This is minor, but I think this part is backwards:
>Most people don’t clearly say that excess winter deaths are a combination of cold-related (from the flu) and season-related (from cardiovascular) deaths, even though something like this has to be true
Isn't the flu season related and cardiovascular deaths cold related?
I don't really think pointing to influenza or other diseases in Africa does much to explain the data. After all, that just pushes the question back one stage: why is it that these flu deaths are concentrated in the winter? If it's because they are more common when the temperature is lower than wouldn't that also support a causal story? You might try and say it's about the worldwide increase in flu during the winter but that doesn't work as the southern hemisphere has winter when we have summer.
I'm going to suggest a different explanation. Maybe it's all just about extremes of temperature being associated with unusual weather conditions which are more likely to lead to things like crop failures (and all the downstream badness including more wild animals dying leading to more opportunities for death). I have to think a bit more about it but the graphs above estimating MMT make me suspect that this is all mostly seeing some kind of mathematical artifact (e.g. that the more extreme the temperature is on a day the more likely it will be to occur during an unusual weather year).
I believe that David D. Friedman has an explanation for "[w]hy would cold places adapt so hard that they did better than warm places?"
In short, I believe the explanation is that it does not make sense to invest in heat regulating equipment or insulation in temperate places (in his example, New Zealand), because they have high fixed costs. Accordingly, houses in New Zealand are very poorly heat regulated (and, although it does not get extremely cold in New Zealand, the houses are much colder than countries with more extreme temperatures). In contrast, to survive in certain places with more extreme temperatures, it makes sense to incur the fixed costs. Once those costs have been incurred (e.g., for insulation), the average cost of achieving the optimum temperature year round is low.
I seem to recall that David D Friedman had this written up somewhere, but I can no longer find it. Since I understand David reads this substack, hopefully he will be able to expand further (and apologies in advance for any incorrect summary).
Wait, no, isn't there a *really* simply explanation here. Generate some random data. It will always have some minimum mortality associated temperature. If you then call the increases in death relative to that MMT that occur at higher temperatures heat related and those at lower temperatures cold related you'll find alot of heat and cold related deaths.
I agree this doesn't quite explain the asymmetry between hot and cold temperatures but I'm going to guess it's something simple about the fact that plants are grown during the hottest part of the year leaving the coldest part of the year more time to do things like fight wars or when shortages are more likely to push people into lower immune activity or making more dangerous choices.
I have little to add aside from linking to my favorite flu-related paper, on the 9 conundrums of influenza
" (1) Why is influenza both seasonal and ubiquitous and where is the virus between epidemics? (2) Why are the epidemics so explosive?
(3) Why do they end so abruptly?
(4) What explains the frequent coincidental timing of epidemics in countries of similar latitude? (5) Why is the serial interval obscure?
(6) Why is the secondary attack rate so low?
(7) Why did epidemics in previous ages spread so rapidly, despite the lack of modern transport? (8) Why does experimental inoculation of seronegative humans fail to cause illness in all the volunteers?
(9) Why has influenza mortality of the aged not declined as their vaccination rates increased? "
The authors hypothesize Vitamin D levels and "Good infectors". Whole paper is worth a read though.
It frustrates me a little that the messaging around covid at the moment is still "We don't know if it's seasonal", when it's been behaving exactly like a seasonal virus all this time.
I worry that the Northern Hemisphere is about to discover that even with a heavily vaccinated population, keeping Delta (or maybe Delta+) covid under control in the winter is a much harder job than keeping it under control in the summer.
As far as I understand it, the expectation of increased mortality at higher temperatures boils down to (no pun intended) the shape of the mortality curve at most cities. The rate of increase of mortality below the optimal temperature is gradual, while the rate of increase of mortality above the optimal temperature is steep. Assuming that the mortality vs temperature curve doesn't change over time (a big if), a given temperature increase causes a large increase in the heat-related mortality and a smaller decrease in the cold-related mortality.
In winter people have fewer fresh fruits and vegetables to eat (especially outside the first world). They also get less vitamin D from sunlight. Worse nutritional status in the population could weaken immune systems and slightly increase the r-factor of any virus. Plus cold helps the virus survive longer outside the body, and incentivizes people to gather indoors. The r-factor of the flu hovers near 1, so those small changes can make it go supercritical or subcritical seasonally. That's my best guess as to why the flu is seasonal.
But in general warmer areas have a higher disease burden due to vectors that can't thrive in colder climates. Warming will likely expand the territory of malaria, and I don't know if anyone is factoring that into their calculation of warming deaths. But maybe that will be moot if someone invents a good vaccine or a clever way to kill the insect vector. There's too much unpredictable human action between the warming and the final consequences to have high confidence in any number of deaths.
-Presumably one way to die while hunting in Greenland involves ice not being as solid as you thought, which is more likely if it's warmer? Do Tibet and the Andes experience something similar with more avalanches or rock/mudslides?
-One group of people who are particularly vulnerable to the cold are the homeless. Is there a relation between homeless population and cold-weather deaths, and is this affected by things like emergency shelters that only open in unusually cold weather?
I find the human ability to adapt to different temperatures fascinating, and I'm not sure I understand it well enough to dismiss the idea that people are dying at 60 degrees F out of hand.
My brothers and I all grew up in a temperate, almost Mediterranean environment: rare to get as hot as 100, rare to get as cold as 25. As an adult I moved to a place where the typical winter temperature is around 0, and in summer it doesn't reach 90. He moved to Mexico.
He visited me once in summer: it was 75-80 degrees the whole time he was here, and he spent the whole trip in a long sleeve jacket with a puffy vest on top. Because he was cold! It certainly wasn't a put on, his internal thermometer had just shifted upwards while mine had shifted down. A couple years ago we had a heat wave where it hit 88 degrees for a week: we were all miserable with the heat, even though I would have been fine with 88 before I moved up here. My younger brother is planning on moving to Sudan and has visited there before, in a region where the typical summer temperature is in the high 90s, low 100s. While he was living in Texas someone who had lived in South Sudan for a few years came to visit and talk to him about moving to Sudan, and that guy also wore a long sleeve jacket and puffy vest his whole visit. In Texas. In summer. He was genuinely cold.
I don't know how the body does it, but if someone can be genuinely cold in Texas in summer because they're used to hotter, isn't it possible that person might die of cold if it hits 50 degrees?
No consideration of the possibility that all this weirdness has something to do with genetic differences between populations? Africans are adapted to one climate, Swedes another. You can speculate all day on what that means, but all we know is that genetics is probably conflating all of this somehow and we can’t know anything until we account for that.
Aren't suicides seasonal? A quick search gives me Wikipedia saying they're much higher in spring and summer, though it sounds like it's about the season and not the temperature. Is this effect too small to be important?
A quick bit of googling found that chilblains can show up at temperatures up to 16° C. No one is dying of hypothermia at that temperature, but that doesn't mean health can't be affected, especially if you don't have access to a source of artificial heat.
My completely speculative take of the scatter plot you you show is that countries to the top-right, i.e. high-temperature high-death countries, look like they could have more homelessness than the ones on the bottom-left. Perhaps it is homeless and almost homelessness that is explaining part of the relation, but I doubt it is much.
I don't understand how the MMT chart for NYC (showing the highest mortality at high temperatures) fits with the NYT deaths-over-time chart (showing the most deaths in the winter). I didn't take the MMT charts to be some sort of adjusted-for-season death rate, it's just death rate vs temperature, right?
It appears that the answer to the question "will global warming cause fewer people to die from the cold?" is "no: it will in fact cause _more_ people to die from the cold".
This depends on whether the "death vs. temperature" distribution stays fixed as the distribution of temperatures moves up, but that naively seems unlikely to me given that "death vs. temperature" is already so highly variable across geography.
Also relevant: did the Grateful Dead prophesy in "New Speedway Boogie" that the end of the world would come with cold-related deaths in high temperatures?
More than half of all Americans die in an institutional setting: hospital, nursing home, or inpatient hospice. All home + road + other deaths combined are less than 50%. The temperature inside a hospital has very little correlation with outdoors temperature, yet we see this incredibly consistent temperature-mortality correlation throughout multiple US and world cities.
If there was a breakdown of temperature-mortality curves based on place of death, we'd have a fairly good idea of whether it has anything to do with temperature at all.
If the correlation was truly a direct causal effect (unusual temperature -> death) then we would see an extremely strong correlation for outdoors deaths, a moderate correlation for home deaths, and very little correlation for hospital deaths. On the other hand, if the correlation mostly reflects seasonal variations in infectious disease, risk taking behavior, diet, etc. then we would see very similar curves regardless of place of death, or even stronger mortality curves in hospice and nursing home settings where the populations have the highest susceptibility to infection.
Here's a well-documented example of heat-related excess deaths: Worst heatwave of my 18 years in Chicago was five days in July 1995, where the temperature peaked at 106 and humidity was very high. The heat caused partial power outages so air conditioners were off at times and even iceboxes lost their ice.
Out of a population between 2.5 and 3.0 million, an estimated 739 more Chicagoans died that week than was normal. From Wikipedia:
"Eric Klinenberg, author of the 2002 book Heat Wave: A Social Autopsy of Disaster in Chicago, has noted that the map of heat-related deaths in Chicago mirrors the map of poverty.[2][7] Most of the heat wave victims were the elderly poor living in the heart of the city, who either had no working air conditioning or could not afford to turn it on. Many older citizens were also hesitant to open windows and doors at night for fear of crime. Elderly women, who may have been more socially engaged, were less vulnerable than elderly men. By contrast, during the heat waves of the 1930s, many residents slept outside in the parks or along the shore of Lake Michigan."
The city government didn't do a good job of responding with cooling shelters or public service messages to check on your aged relatives, although after the disaster they improved their response notably in subsequent heat waves.
Who dies of 12C weather & why very cold cities have fewer cold-related deaths than hot countries in Sub-Saharan Africa has everything to do with the simple fact that cold places tend to be rich and hot places tend to be poor, and poor people in hot places have exactly one way of dealing with cold weather they aren't used to -- they build fires.
Remember, we are talking about people too poor to own sweaters, or boots, or woolens of any kind. Their only shoes are sandals. They live in huts with zero insulation, because they are made for air flow in hot weather. And they often sleep outside, with thin sheets to serve as blankets, if any.
Under these circumstances, 12C or even 15C or 18C is absolute torture, especially when your body is not used to it. I grew up in a tropical country and despite almost 20 years in the US I am still miserable at any temperature below about 18C (65F). And I own all the winter paraphernalia I need!
So what do you do when it's a bitterly cold 17C and you have no way to keep warm? You build a fire, and try to keep it going all night. And you have no actual fireplace, or chimney. I wonder how many of these winter deaths in hot countries are actually a consequence of fire.
Climbers head to the Himalayas and the Andes to mountain climb in the summer and it's fairly dangerous. Not sure if an Everest avalanche tourist death in late spring might be counted as a Tibetan heat related death or not.
Death by hypothermia being more common in hotter climes actually makes a good deal of sense to me. Yes deserts are hot, but they also shed heat incredibly quickly once the sun goes down as anyone who's spent a fair bit of time in Africa, the Middle East, or even Utah can attest. Getting caught outside after dark without a blanket or warm clothing is a legitimate and widely recognized danger.
That said I don't see how that would translate to people dying of heat-stroke in Greenland. A rash of malfunctioning saunas maybe?
When we are talking about sub-Saharan Africa, what months are winter? Does the flu season actually correspond with the lowest-temperature months in all these places or does the fact that it's flu season in other populous parts of the world change that?
Not particularly happy with any of the studies either, or our ability to draw conclusions from them.
But one thing I found interesting was the global mortality rates with income-based adaptation (like more a/c) mentioned in Bressler. Logically, as people get richer, they can offset some of the heat-related deaths by investing in adaptation, and the higher emission mortality rate decreases from 6.2% to 4.2% when this effect is included (a not insignificant effect).
But one piece that is missing is many proposals for mitigating climate change (e.g. a carbon tax) have economic costs that will compound and lower global economic growth over time. If income-based adaptation to heat can have a significant impact to global mortality projections, how much of a decrease could the foregone income from lower growth rates have bought (across not just heat adaptation but all healthcare-related investments)? Isn’t it possible that the effects on mortality of having $10’s or $100’s of billions less of global GDP over a period of 60 years would swamp any direct change in the mortality rate from temperature changes like the ones forecasted?
This, of course, would say nothing about whether those costs or mortality benefits would be equitably distributed, but it’s a piece of the puzzle that is rarely pointed out in papers that seek to quantify specific costs of letting the temperature rise.
I suspect one reason why cold cities over-adapt is that some of the important ways cold is dealt with tend to be fairly binary. That is, you aren't really optimizing houses for a particular temperature, you're optimizing them for heat retention (within some bounds, of course, but it's not a very granular decision). You either have heating infrastructure or you don't (and if you do you either have laws and norms about making sure people get heating even if they can't really afford it or you don't). Sure there's more gradation at the personal level with things like various jackets and coats being appropriate for various temperatures, but at the level of construction and governance there are big, binary choices and as they get made they push you into being over-adapted.
Three comments. The first is a point already implicit in your discussion, but one that I think you missed earlier and many people still do. Heat mortality isn't just, probably isn't mainly, people going out in a heat wave and dropping dead. Cold mortality isn't just people freezing to death. Those are dramatic examples, but probably more important are the people who are made a little worse off by heat or by cold, a few of whom die sooner than they otherwise would.
The second is something that I noticed looking at the latest IPCC report and that they, I think, never mention. The effect on heat or cold-associated mortality depends on how much warmer climate change makes winters, how much hotter summers. The report gives projections for the change in how hot the hottest day of the year will be in various places with various amounts of global warming. It has a chart showing how cold the coldest day of the year will be in various places with various degrees of warming.
I looked at how much hotter the hottest day got in hot places and how much colder the colder day got in cold places. The answer was that the coldest day in cold places got two to three degrees warmer for every degree of global warming, the hottest day in hot places got about one degree warmer for every degree of global warming. Warming makes winters milder and summers hotter but, at least for the places I looked at, the former effect was two or three times stronger than the latter. The report never made that comparison, provided the necessary information in different places and contexts for warming and cooling.
Similarly, the report routinely said that climate change had both effects but paid attention almost entirely to the effect of hotter summers. That fits my general view of the report, that the authors honestly report their results but are looking for reasons why climate change makes things worse, not reason why it makes things better. If you don't look for something you are quite likely not to find it.
I was thinking in terms of temperature extremes and had not yet read your post, so it didn't occur to me to look at the effect of warming on cold extremes in hot countries or on hot extremes in cold. Looking at those, the pattern is less extreme, but the qualitative difference remains — in most but not all places, climate change raises minimum temperatures more than maximum. I find in the Summary for Policy Makers:
"Some mid-latitude and semi-arid regions, and the South American Monsoon region, are projected to see the highest increase in the temperature of the hottest days, at about 1.5 to 2 times the rate of global warming (high confidence). The Arctic is projected to experience the highest increase in the temperature of the coldest days, at about 3 times the rate of global warming (high confidence).
My third comment has to do with the various attempts to actually measure the mortality effects. None of them should be trusted, at least until you go over them carefully. If an honest and intelligent person solves a simple problem he is quite likely to get the right answer. The more complicated the problem is, the more his answer will reflect either what he expects to find or what he wants to find. For an example outside of climate issues, consider the history of measurements of the charge of the electron.
Kampala, Uganda not only never really gets cold, it also has practically no seasonal variation in temperature. If someone has actually calculated temperature-related excess deaths for it, that must be from random weather changes, rather than seasonal changes.
Given that Kampala or similar places likely have no heating at all, and little insulation, a cool temperature outside corresponds to cool temperature inside. If the relation between colder temperatures and heart attacks exists even at near-room-temperatures, it's plausible that there are more heart attacks in Kampala at relatively cooler temperatures.
Scott, how long does it take you to put together a post like this? Just finding and processing these disparate sources on this out-of-left-field topic is something. But you actually synthesize them into a meta-study, which you wrap head to toe in engaging prose. (Or are there some behind-the-scenes researchers or editors contributing to this production?)
Feature request: Provide subscribers an estimated Hours To Produce figure on your posts?
I don't know if this is supported by evidence at all, but I think it's one possible solution to the paradox: suppose that temperature-related deaths are, for whatever reason, extremely non-linear with temperature. For example, suppose that you get 90% of heat-related deaths between 95F and 100F and 90% of cold-related deaths between 60F and 50F. Then in the hottest countries, heat-related deaths might be spread so evenly through the year that you couldn't identify a relationship between hotter days and more deaths. Similarly for the coldest countries you couldn't identify the cold-related deaths.
But even if something like this was going on, I think it could only explain the very hottest and coldest countries - if the trend holds up when just looking at the countries in the middle, then I don't think this would explain anything. From eyeballing the graph it seems like the trend does hold for the middle countries.
> Everyone says that global warming will worsen mortality from heat. I’m a bit confused by this also
There's an asymmetry here that might be worth noting: when it's cold, you can usually put more clothes on to warm up. There is only so much you can take off when it's hot.
(I've always found that frustrating, because I'm increasingly incapacitated by temperatures beyond 75F.)
A possible explanation for the data in Bangkok and other tropical parts of the world - the "cold" season is not just winter, it is also the rainy season when the disease burden and mortality go up every year due to a whole host of diseases of which flu is just one of them. Examples of other illnesses include dengue fever and leptospirosis.
This is certainly the case in my home state in India, Kerala. Mortality goes up in the rainy season which is not cold by any measure. But the absence of sunlight, presence of stagnant water etc probably does as much damage as colder weather does elsewhere.
I think these sorts of studies miss some huge confounding factors related to some of the details that excess death numbers just cannot get at. In Michigan, where I live, we get a few pretty severe hot days in the summer and a few pretty severe cold days in the winter. When it’s severely hot out, we have old people dying in un-air-conditioned homes, since many here still don’t have central air and many old people cheap out about putting in window units until it’s truly hot out, not to mention farmers and construction workers who have to work in the heat. On the other hand, we get fairly few direct freezing to deaths in the winter because everyone has heat and most people avoid activity when it’s that cold. We get far more winter deaths from icy roads or heavy snow or the heart attacks from shoveling snow than from the temperature per se. This is compounded by the fact that below about 0*F we tend not to get much snow, so much of the direct causes death decrease below a certain temperature.
I think this analogizes well to the pandemic, actually. Despite the lockdown orders here, and despite the number of people working from home, traffic deaths went up in 2020 vs 2019. Way more people took advantage of empty freeways and the state troopers explicitly saying that they weren’t going to interact with people early in the pandemic just to write tickets to do dumbass car racing at 120 mph on the freeway and wrapped their shiny Shelby 350s around a bridge abutment. Similarly, some of the stay at home prevented flu deaths, but increased, say, cancer deaths due to delayed diagnosis. These things are often deeply complex systems with complex causation and I see no reason why temperature related deaths would be different.
The thought is that I am surprised you didn't mention increased traffic fatalities as one of the possible contributors to excess cold deaths. Obviously less relevant in places that don't get snow/ice in the winter, but where I am from traffic accidents do go up considerably once the roads are covered with winter yuck.
The anecdote:
It probably doesn't shed any direct light on the human data, but when I was growing up my family saw a very clear pattern in seasonal mortality of our flock of pet chickens. We typically had around 20-25 at any given time, and most only live to 9-11 years (actually somewhat bimodal with a peak at 5-6 and the other around 10) so we got a fair number of data points, and deaths of 'old age' clustered around early winter and mid spring. The early winter makes sense, they had an insulated chicken coop with an electric water heater and an electric heater in the coop, but they were still essentially living outdoors and the cold is an extra source of stress on the oldest/frailest. But the odd thing was the spring peak, which was actually the higher of the two. it was before the summer heat came in, but still well into spring and we could never figure out what the stressor was when the weather was that mild except that it must have something to do with the change in temperature moreso than the absolute temperature, especially since the winter peak was well before the coldest part of the year.
Don't extreme temperatures cause mortality in a lot more ways than listed here? They just sort of generally take a toll and make you more likely to die if you're sick, heat makes people more violent, cold makes people less social, etc. In places that aren't super food-secure they cause famines.
Just so I've got a handle to work with the equal and opposite ideas of more cold deaths in hot places and hot deaths in cold places, I'm going to refer to them collectively as environmentally oppositional deaths (EODs). So my first thought was that the EODs might be caused by excessive environmental controls: setting the A/C too low in hot places and cranking the heater too high in cold places.
There's a meme in some places that the weather forecast is always wrong (statistics to the contrary notwithstanding). In places where this idea is pretty widespread, would people develop a habit of compensating for how wrong the forecast is? Would this lead to unexpected extremes, ones bad enough to up the number of EODs?
Anecdotally, recently a small cold front went through, so we turned the heater on for the first time this season to brace for it and to get the cobwebs out for the months ahead. Unfortunately we didn't know how small the front actually was, because in the middle of the night we were woken up by how hot it was. I checked the thermostat, and while the heater was set to only 70, the temp gauge said it was 77 in the house! That's 7 degrees of difference, and compared to the usual climate here, that was a rather mild night. If something like this happened in a place with more extreme temperatures, I can't imagine how bad the temperature differential might be from such a mistake, and how many EODs that might lead to.
I would like to see these numbers controlled for schools in session. I find it highly likely that many seasonal diseases are seasonal because schools are usually packed full of children who pass illnesses to one another, are often asymptomatic or lightly symptomatic, and then go home to their families who are more susceptible.
This feels like the kind of post where it might be worth just calling up someone in the field and asking them questions for 45 minutes. I know that has never traditionally been the format of this blog but it would probably be a shortcut to a lot of interesting stuff that hasn't been synthesised in any published papers yet. In my experience, not every scientist you email will want to talk to you, but a lot of them will.
One point which has not been stressed here at all is the role of humidity especially for feeling cold. The effort to keep up a certain temperature increases with humidity due to higher heat capacity and conductivity of wet air (20C in water is quite different than 20C in air). This effect should be expected to be higher in warmer regions where humidity is higher and the number of layers of clothes is less.
We have examined relationships between mortality and cold and hot weather effects in Hong Kong. Basically the cold weather effect on mortality is pronounced and is independent of influenza rates. Also almost all causes of death are affect (except for cancer and accidents) not just cardiovascular deaths:
Hong Kong is a good place to test this as the weather during winters varies considerably. During some winters temperature rarely go below 15C while others have been characterized by long cold spells (by our standard a cold spell has temperatures < 15C). During those winters with colder temperatures we see a lot more excess mortality. So not seasonal (at least not here).
Seasons in the Andes are not like seasons elsewhere. Winter is sunny and dry, with blue skies; summers are damp, and it's cloudy, and not that hot. (There are also mudslides during the summer, but much of their damage is to lowland regions lying further downstream.) Yes, in winter, it's chilly in the early morning, or even mid-morning if you are in the shadow (and it's temperatures in the shadow that are usually recorded, no?), but there's plenty of radiant heat from the sun. Of course too much UV can also cause problems, but generally not immediately - you could get skin cancer or sight problems later on. I'd certainly say winter *feels* healthier (to me, and to anybody else who is somewhat affected by asthma/allergies), at least in the regions that Peruvians think of as having "moderate altitude" (< 3750m or so).
While we are at it: global warming affects much more than just ocean levels. Andean glaciers are melting rapidly. Momentarily, the effect is not entirely bad (more water! good harvest! ah, ok, mudslides, but those are partly further down), but in the medium to long run, it's bound to be pretty terrible - without glaciers and less rainfall, the entire region could become basically uninhabitable (or really uninhabitable, according to some projections).
I'd expect regions to adapt according to comfort, which might be more than is needed to not die. So from a perspective that's only about death rates, it looks like over-adaptation.
Accidents are the number 3 cause of death (in the US anyway), and it seems plausible that you’re more likely to have an accident when extreme conditions force you to do things differently than normal. Maybe?
Also, FWIW, if their model uses 0.5 degree latitude by 0.5 degree longitude squares, that means the equatorial squares are much larger than the polar “squares”, though I’m not sure that helps explain anything…
I don't have time to check this carefully right now, but keep in mind that car crashes occur more frequently during cold months. Northern countries have methods of dealing with slippery roads such as spreading sand or mandating use of snow tires on vehicles. I assume that warm countries do none of these things and instead get surprised when the occasional cold month hits them.
My personal experience is that the change in temperature or any environment is a challenge to the body. 16°C in October feels cold, the same temperature in April makes me thinking about wearing nothing but a t-shirt (and if you see people wearing t-shirt in April - that are tourist from scandinavia visiting Germany).
How does this effect sub-sahara africa? People are used to constant temperatures during their whole live, and they are not trained to handle changes. I know a man in Bujumbura, Burundi, who went to hospital in Nairobi, Kenia. He felt uncomfortable because it was too cold (and we are talking about 10°F colder temeratures).
So the environmental changes could be more challenging to people in areas with less seasonal differences.
1) You don’t buy the idea of 12C being a dangerous temperature, but have you ever spent a significant period at that temperature in an uninsulated building/outside? It’s freezing!
2) That said, Kampala’s annual temperature curve is basically flat, with a daily mean of 22-23 C all year. The way the main paper fits functions on top of functions, it seems inevitable that trying to draw a signal out of a 1C range will result in nonsense.
3) Nepal/Tibet could be related to the the monsoon, which coincides with high temperatures.
4) Does this post on the harms of cold have anything to do with your time in England?
I wonder whether the variability of temperature could play a role. That is a sudden heat wave or cold snap is worse for mortality than if it is always pretty cold or pretty warm. The nordic countries that have low winter excess mortality also have pretty stable climates. Iceland which had no winter excess death has a really low temperature variability (at least in the populated parts). Reykjavik has a daily mean of 0.7C in January and 11.6 in July and record cold of -20C. Nome in Alaska is at the same latitude and has a daily mean in January of -15C and record low of -54C.
- R-nought for the flu gets above 1.0 in the temperate northern part of the world in, say, November-March and in the temperate southern part of the world (e.g., Buenos Aires, Melbourne) in May-September.
- People from the temperate world travel to the equatorial world more or less year round.
- Temperate people are more likely to bring flu with them in their homeland's winter and infect equatorial people they are visiting.
- There are vastly more people living in the temperate north than the temperate south.
Prediction: More equatorial people get flu in the Northern winter than in the Southern winter.
Stockholm is actually not very cold. The average minimum for January is -3, same as New York, as compared to -21 in Novosibirsk. Still, it's cold enough that I'm surprised not to see any mention of the lives lost to slipping and falling on ice/snow (I think about half a percent of deaths), or the QALYs lost to injuries from slipping and also from the fear of slipping and the isolation brought by such fear (among the elderly).
Best scientific treatment I have seen so far on variations in temperature-deaths, and a nice open-ended discussion of possible implications of global warming.
Scott asks the question: Is it reasonable to assume people in cold climates over-adapt to the cold, relative to people in the South? (quote: "Why would cold places adapt so hard that they did better than warm places?")
I think a theory can be formulated. At least I have got one, based on living in the North of Europe and sometimes travelling to the South of Europe to escape winter – only to find myself almost freezing to death in some rented house in the South. (Ok, n=1, but wait for the theory)
Here is the theory: People in the North know that when winter comes and it gets cold, it stays cold for a long time. You cannot wait it out. So you have to put in the money to get central heating and those triple-glassed windows.
While people in the South know that when it gets cold, it usually does not stay cold for very long. If you brace yourself, the cold spell is usually over in three weeks max. You can brace yourself to live through three weeks of cold, but not four months. So you do not adapt at all.
Plus, to some extent people in the South must do the opposite: They adapt their houses to the often very warm summers. That is why I have never frozen more than in the South. Old stone-built country houses in particular (where old people often live), are built to keep the heat out in summer. Which makes the houses ice boxes in winter.
…for US people, a similar logic is captured by Mark Twain’s dry observation: “The coldest winter I ever lived was a summer in San Francisco.”
Finally getting to the testable hypothesis: If I am right that people in the South sit out the cold while people in the North adapt to the cold, we should get excess cold deaths in the South, but only in years with unusually long Southern winters; i.e. when the presumption that “the cold will pass” is not borne out. Scott’s information that cold deaths usually take place 14+ days after the cold spell starts, fits with this assumption.
To test this hypothesis we would need data not only on winter temperatures in different countries and across time, but also variations in how long the winters last. Cold deaths in the South should peak in years where winters surprise everybody by being long.
Finally, a bit of travel advice to ACT readers: Be careful if you live in the North and are tempted to rent one of those picturesque and suspiciously cheap old rural stone cottages in the South to escape your own winter! Speaking from bitter experience….
Confounding this is the fact that Scandinavian countries are not only prepared for cold weather, they do so in rather safe ways. Electrical or natural gas heating, or when wood is burned it is in airtight stoves with well-maintained flues. Here in Nova Scotia house fires and flue fires are common winter occurrences, but we can't afford to do things as well as the Scandinavians. But consider the case of sub-Saharan Africa: most cooking and heating is done over indoor open wood fires in rural areas. Even in cities the electricity supply is unreliable. Open fires mean increased COPD from breathing smoke, and that in turn means respiratory infections are likely to be more dangerous or even lethal. My wife started an orphanage for AIDS affected or AIDS orphaned kids in Kenya, and goes there yearly. She notices how they feel the cold - even when it seems hot to her they will put on coats as 20ºC seems bloody cold to them. So more wood gets burned. More risk of fires, and more respiratory infections from huddling indoors, and those infections will be more deadly in lungs that have been inhaling woodsmoke. Add to that the immunosuppression and general weakness from endemic TB, malaria and AIDS, and you can see why deaths skyrocket in the cold season. One thing we have done is to encourage the use of rocket stoves, which burn less wood (in short supply) and produce far less smoke. There is even a charity dedicated to encouraging their use - see https://www.aidafrica.net/rocket_stoves/
I'm taking the liberty of posting before reading all the comments. If lack of sunlight is a factor in winter deaths, then there should be a weaker winter death effect closer to the equator, even allowing for warmer temperatures.
If excess mortality is caused by temperatures outside the usual range, then moving the range up isn't going to lead to fewer deaths from cold.
For reasons I'm not going into, I live in Philadelphia without air conditioning. This gives me a different understanding of the effects of challenging weather than a lot of other people seem to have.
The high and low temperatures only give a modest amount of information. For *how* *long* was the temperature at or near the high? What were the lows like-- how much of a chance does the house have to cool off at night?
The worst summer weather I experienced was in Philadelphia in 1995. Two weeks of high of 110F and low of 85F, with high humidity. The air felt like it was so heavy it was hard to breathe.
Incidentally, the past three summers here have been relatively tolerable. Previous, the humidity was always pretty high, and I thought that it was inevitable because I'm living between two rivers. That theory is wrong-- the past summers have been at least as hot as the usual (highest temperatures in the 90Fs), but with moderate humidity. I have no idea what's going on.
From experience living in a multicultural family, I believe the over-adaptation to cold is true.
The (simplistic) rational is as follows:
- If you do not wear the appropriate clothing in mild European climate in winter, you might catch a cold. Big deal. People end up wearing unappropriate clothing out of laziness, wanting to look cool/strong (teenagers), and eventually habit.
- If you do not wear the appropriate clothing in Russian winter, you... die. Hence people are much more careful, and the intensity of this effect is non linear.
Slightly counter-intuitive, probably controversial, but all my personal data points support the hypothesis so far.
I haven't read the papers, but does all of this relate to natural deaths only? Because I would imagine there to be a pretty strong link between suicide, car accidents, falling etc. with the cold (and thus dark) season. Sure, these don't make up the lion's share of deaths, but they surely play a role.
It's really hard to hypothesize about causes without more info, like:
- Separate deaths from transmissible diseases
- Separate deaths from exposure itself (i.e. "freezing to death")
- Attempt to account for "when people spend more time indoors" - this probably varies a lot by region, as some regions consider it "too cold" at different times than other regions. It's not settled fact that flu spikes in winter for ventilation-related reasons, but it's at least part of the equation. Related interesting question... when it's way too hot and everyone stays inside, does that lead to more disease transmission?
Thanks. I realize people are quite confused about this; someone even asks if hot places have winter. But I want to remark at least three main issues with this whole analysis that make me very suspicious about cross-country comparisons regarding deaths, temperatures and seasons:
1) CONFOUNDERS: distinguishing the “temperature factor” and “winter factor” is harder than we think, especially if what you want to measure is the impact of climate on health. It’s not just that there are too many confounders, it’s hard to define what is a confounder and what is causally relevant. For instance, winter is the dry season in Brazil: prices and allergies (because of dust) spike; global warming will likely make this worse. On the other hand, in higher latitudes, you have way less sunlight and significant behavioral changes; global warming may or may not help with that.
2) ADAPTATION: I wonder if physiological adaptation is underestimated. Acclimatization takes a while to be optimal – think about adaptation to changes in altitude; so, gradual transitions between temperatures should be optimal. But in tropical climates, you don’t have that: living in Sao Paulo, you can have 30ºC on a hot dry winter day, followed by a cold or hypothermia with 15ºC on the following rainy evening.
3) VARIANCE and MEASUREMENT: notice that some of the linked papers (those I checked, AT LEAST) used data on the average temperatures (usually the mean between the max-min on the same day). Not only this neglects wet-bulb temperature and windchill factor, it also equates a wet day with min of 15ºC and max of 35ºC (I hate those days) with a pleasant dry day ranging around 25ºC.
I wonder how the results would look when compared with seasonal temperature variability, as opposed to how hot or cold it gets on an absolute scale? Humans seem to benefit from a certain amount of variance, so maybe people who live in places where the annual temperature is between -10F and 60F are better adapted to deal with general physical stressors than people who live in places where the annual temperature is between 70F and 90F.
1. Let's say someone had a heart attack/blood clot because of a cold day. You'd expect to see increased mortality about a week or so later, because, while some people would just drop dead, others would go to the hospital and die there. A group looked a weather variables and incidence of DVT (blood clots) and found that around 9-10 days after a rainy day, or a windy day, or a day with low atmospheric pressure (more on that below), there was an increase in blood clots about a week later (source: https://pubmed.ncbi.nlm.nih.gov/19806252/#affiliation-1). It seems more plausible that these effects are mediated by inactivity than the effects of weather on our physiology.
2. Hawaii has VERY little variability in seasonal temperature (coldest month with a high of 80F, hottest with a high of 88F), but has about the same seasonality to respiratory infection and cardiovascular disease as other places with more variable temperatures (source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC28593/pdf/1946.pdf). Please click through and look at how smooth the temperature curve is while the respiratory infection and cardiovascular disease curves whip up and down every year. It just does not seem biologically plausible that temperature effects on physiology could account for such a significant amount of variation. Another way to say this; I don't think increased blood viscosity or peripheral vasoconstriction due to *slightly* colder weather could be causing increased cardiovascular mortality in Hawaii.
3. Inactivity is high associated with all cause mortality (https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2783711) though it's tough to determine causality since maybe people who are sick for other reasons move around less rather than moving being protective (though it does seem that a preponderance of evidence suggest that, all things being equal, not moving around much is bad for you-if anyone thinks there's good evidence to the contrary please let me know).
4. Re: association between low barometric pressure and blood clots I brought up in (1). I think even a short period of inactivity (I'm talking a few hours) likely significantly (but slightly) increases your risk of death in the short term. Case in point, physicians are trained to ask if you've recently taken a long flight when you come in with a blood clot. The reason is that the way blood returns from the legs back to the heart to get recirculated is by being squeezed by the leg muscles during normal activity. When you sit in a cramped airplane for a transatlantic flight, you might sit more or less perfectly still for >6 hours. Blood that's not moving is MUCH more likely to clot, and so you can get a blood clot.
The authors of the weather vs. clots study noted the strongest association between low atmospheric pressure and incident blood clots. I interpret that to mean that days with low atmospheric pressure (overcast, windy, rainy) correspond to lazy, inactive days at home. They wonder if there's a link between the low cabin pressures in airplanes and blood clots, in addition to the activity. Not sure how you would tease this apart.
I don't understand the definition of "cold-related death". Is it strictly death from hypothermia ? Is it death from seasonal illnesses, which are caused by the cold ? How far up the chain of cause and effect are we going to follow ? If a person is driving his car to work one day, hits a patch of black ice, spins out of control, and plows full-speed into a pedestrian, then did that pedestrian "die from cold" ?
First, the causes of death. Heat-related causes of death are generally pretty direct; dehydration and heat stroke. They also predominantly hit the medically frail, but will also hit those with less experience with heat worse; as somebody who has lived in one of the hottest places in the country, I recognize the symptoms of heat exhaustion, and immediately rectify the situation. Somebody without experience with heat might not notice their heat exhaustion until they're too mentally addled to actually do anything about it.
Cold-related causes of death include both direct and indirect causes, however. For direct, there is hypothermia and exposure, which I think will predominantly affect the medically frail. But there are also cold-related accidents (slips/falls and traffic incidents), and also being snowed in, which can cause people to die of apparently unrelated accidents (bleeding out while waiting for an ambulance after a kitchen accident). These can be mitigated to a significant extent by appropriate local investment (snowplows, salting and sanding roads), but this is only done if it makes sense to make that investment.
For the indirect cold-related deaths, I think are notable in that they are not as limited to the medically frail. I'd hazard a guess that the average cold-related death costs far more QALYs than the average heat-related death.
Re: heart attack deaths, the paper you linked seems to be about blood thickening below a specific temperature rather than relative to local baseline. So maybe places like Stockholm are cold enough year round that people's blood isn't much thicker in the winter than it is the rest of the year?
It seems to me that the explanation about vulnerable (near death) populations is the most probable. It explains the lag time between cold weather and deaths (they get sick first) and also the tendency to be opposite in cold verses warm locations. A location that's unusually warm may help stave off a person getting sick, but a 10-20 degree temperature drop, even if the resulting temperature is well above what's needed for survival, would be enough to take their already frail body to a place where death is much more likely. In a truly cold place, that person would have gotten sick and died earlier (general death statistics regardless of temperature), or have been placed in a location where temperature differences are less of an issue - i.e. the insulation discussion, where Swedes are used to being cold and better prepare their populations for it.
In this theory, it's not acute cold that causes death, but instead lower temperatures that result in sickness and then death. Heat deaths, on the other hand, tend to be more sudden and directly related to high levels of heat, but would affect similar populations. Heat deaths come from heat stroke and other direct effects, rather than opening a person up to sickness.
Did you consider traffic fatalities in the winter? Anecdotally and from basically everybody I've spoken to, winters are more dangerous for driving due to snow, slush, wetter conditions, overcast etc.
It’s kind of fun to figure out where in the world commenters are sitting at their keyboards.
Unless they make an explicit mention of their location it’s enjoyable to see what can be inferred by their units of measure, local season mentioned, acronyms used or distinctive spelling of English words.
I am amazed by the global reach of ACX. Western Hemisphere and Eastern. Northern and Southern.
Our host has touched on how his readership has spread since his - I’m searching for neutral terminology here - let’s just call it interaction with the NYT.
No doubt it was traumatic at the time but the result sure seems like a long term net positive.
I'm wondering if that's a missing factor here. Is it less about the temperature and more about the humidity and whether it's raining? I'd be curious to see what mortality is like during rainy vs sunny periods, since that seems to correlate with temperature and could resolve the confusion about why the temperature differences for when mortality starts going up are so big from place to place.
I can't cache this out in detail, but I wonder if the odd global MMT results are partly just statistical artifacts. Like, sometimes the tails of distributions are the weirdest, least-normal parts (so maybe hottest and coldest places will break the model), and grid squares with smaller populations will have higher variance (e.g., Greenland must have a small population; thinking of that Andrew Gelman county-level rates of stomach cancer example).
I once treated someone for the beginning symptoms of frostbite in 60°F. I was so surprised I checked her several times before bringing her in and beginning treatment.
"I find this hard to analyze because I still don’t really get why cold cities over-adapt and end up with even lower mortality than the warm ones."
Just a theory. But because cold cities *know they are cold*? Whereas in warm cities, any increase in death might either not be particularly noticed, or not attributed to the temperature - because that possibility simply won't enter citizens' or policymaker's minds. After all, they're not cold cities!
Put another way, 'cold-related deaths' are simply more salient in cities that are already cold.
"I think the idea is something like if an extreme weather event kills lots of people one year, the next year extreme weather events will kill fewer people than normal, because a lot of the vulnerable people are already dead."
I wonder if there is evidence for this from, say, bad flu seasons - or indeed covid.
Extremely low confidence explanation for some of the weirder data:
Perhaps the human body, over long periods of time, adapts to given temperature ranges? Eg, someone from Uganda might find 80 degrees to be uncomfortably cold, with some of the associated dangers, as it’s on the low end of what their body has experienced. I don’t know enough to propose any mechanisms for this, but it seems like the sort of thing biological systems would cook up.
Anecdotally, I’ve known transplants from Florida to NYC who complain bitterly about temperatures that a local person would find quite comfy (~70 degrees).
Your central source (Zhao et al) didn’t collect data on mortality in the places you’re most curious about -- Tibet, Greenland, central Africa, etc. They collected data on mortality in 43 countries (see fig. 1 -- it’s mostly high-income or middle-income countries) and used that to train a model that predicts the temperature-mortality function based on “meta-predictors” like GDP/capita and Köppen–Geiger climate classification. They didn’t look at any mortality data on Greenland -- they just look at the meta-predictors for Greenland, and use that to predict the temperature-mortality function for Greenland. They use that, plus Greenland’s population and temperature history, to guess how many heat-related and cold-related deaths it has. So the lack of curiosity about Greenland isn’t because they’re ignoring a strange real-world phenomenon -- it’s because they’re ignoring the strange behavior of their model at the edges of its distribution.
Note that Tibet, Greenland, and the Andes are all in the same Köppen–Geiger climate classification -- “ET” on the Wikipedia map. It seems likely that the training data included some Andean location with weirdly high mortality sensitivity to warm temperatures, and the paper’s model generalized from that to the few other populated areas with climate classification ET. Maybe that was a good generalization! Maybe whatever is causing high sensitivity to warm temperatures in the Andes is also true in Greenland. But the paper doesn't have Greenland mortality data to test that.
Exposure to cold temperatures has been shown to encourage fat loss and possibly help with diabetes. There are multiple mechanisms: other than simple thermodynamics, the human body adapts to cold temperatures by producing brown fat, which consumes calories to produce more heat in order to maintain body temperature.
This could explain why people in colder climates seem to be doing better overall: they're losing more fat naturally and improving their BMIs.
This link is a decent starting point, if you want to know more you should search for Ray Cronise (a former NASA scientist) and Tim Ferriss, a health and fitness author. They were among the first to popularize this effect AFAIK.
Scott, you spend a lot of this post discussing whether seasonal effects (rather than temperature effects) are driving the cold-weather deaths. But I think the paper is trying to control for seasonal mortality effects, and just focus on the excess mortality (excess relative to seasonal trends and other trends) associated with cold (or hot) days.
“...in the first stage, the temperature–mortality association for each of the 750 locations was estimated by use of a quasi-Poisson regression with a distributed lag non-linear model… where… ns is the natural cubic spline for time with eight df per year to control for long-term trends and seasonality”
They might do a bad job controlling for seasonality! But I would be very surprised if the cold-weather mortality they observe is mostly seasonal.
I’ve dug into this literature for a previous project. Despite the model’s strange behavior in low-population areas, my sense is that it’s probably doing a decent job estimating the temperature-mortality relationship in rich and middle-income countries. But if you want to use any of this to make inferences about the mortality cost of climate change, you need to reckon with a few other details:
The paper’s training data didn’t include any low-income countries. (See my comment on Tibet and Greenland, for a discussion of how they only train their model on a few countries.) The closest they get is the Philippines, a lower-middle-income country. (This is a welcome addition -- previous papers in this literature, like that from the Climate Impacts Lab at Chicago, only used upper-middle income countries like China and Brazil.) From what little data we have, it seems like infant mortality is much more sensitive to high temperatures in low-income countries. (See https://www.nber.org/papers/w24870. This makes sense: if you can afford any climate control -- a swamp cooler, a neighbor’s cellar -- you use it to protect infants on a hot day. So infant mortality is a lot less sensitive to heat in lower-middle income countries than low-income countries.) So, if you use this paper to estimate the effects of warmer temperatures on mortality, you’re going to miss a lot of infant deaths in low-income countries.
The papers you’re citing combine deaths across all ages. But the excess deaths on cold days are concentrated among the elderly, whereas infants disproportionately die on hot days. (You can get this result by playing with the data from the appendices of this paper: https://www.nber.org/papers/w27599) If you care more about the death of an infant than an elderly person, then this pattern will significantly increase the net mortality costs of warmer temperatures.
When economists try to turn these temperature-mortality functions into a “mortality cost of carbon”, they often assume perfect adaptation -- i.e. if temperatures in Delhi start to look like Kuwait City, well then everyone in Delhi will live like people in Kuwait do. Never mind that they may not be able to afford the air conditioning that makes Kuwait livable.
And then of course, none of this captures the mortality cost of stuff like climate-induced migration. Desertification of the Sahel, flooding in Bangladesh -- those are going to drive migration and conflict, and those mortality costs will be significant too.
"Why would cold places adapt so hard that they did better than warm places? I don’t know, but this is what everybody says."
Adaptations aren't continuous, they're discrete - e.g. if you already have a heating system, if it gets extra cold you can turn the heat up a little more, but if you have no heating system you will die.
> When you’re skeptical of complicated models, sometimes it helps to go back to the rawest data you can find. So here’s a graph of mortality rates in New York City over time.
But that's not the rawest data you can find. The rawest data is the number of people in New York City before checking what rate they're dying.
> If growth mindset was so great, you would expect fixed mindset people at Stanford to be as rare as, say, people with less than 100 IQ are at Stanford. Given that you will search in vain for the latter but have no trouble finding a bunch of the former for your study on how great growth mindset is, it sure looks like IQ is useful but growth mindset isn’t.
But I would drift one degree away from the rawest of data, because there's an elephant in the room: wealth. You talk about "cultural adaptation", but a lot of "cultural adaptation" is pretty obviously only posssible with large amounts of wealth.
> The worse your climate, the more likely you are to have good central heating.
Good luck having good central heating without wealth.
> Stockholm doesn’t get any increased mortality from the cold, no matter how cold it gets. Plausibly that’s because they’ve organized their lives and built environment around surviving cold winters.
There are a lot of people in Stockholm. But Stockholm is very wealthy. If Stockholm were not so wealthy, they would not be able to sustain so many people in such a hostile environment.
> I’m not entirely convinced by this story. Shouldn’t this mean that everywhere has the same level of excess death from the cold? Why would cold places adapt so hard that they did better than warm places? I don’t know, but this is what everybody says.
Cold places adapt better to everything. And yes, cold places really do adapt so hard that they do better than warm places. And the reason for that is because having a large enough population to be studied, in a cold place, is very very very strongly correlated with wealth. Cold places, or rather, the people *in* cold places, are wealthy, and wealthy people adapt better to any environment.
And why are large populations in cold places necessarily so wealthy?
There are places on Earth that reached large populations despite lacking great wealth. All such locations have one thing in common: they are warm.
This patterns *jumps* out of the data. You will search in vain for cold regions that reached large populations before acquiring large amounts of wealth, but warm regions have no such difficulty.
The one thing we can say a priori about the winter death rate in New York is that it can't possibly be very bad, because if it was, then there wouldn't be so many people in New York.
Which is a more dangerous location for children to play: a backyard swimming pool, or an interstate freeway? Well, many children die each year playing in swimming pools, and very few playing on interstate freeways. Therefore swimming pools are more dangerous. Do you see the obvious problem with this logic? The reason there aren't so many children dying while playing on interstate freeways is because there aren't so many children playing on interstate freeways. And the reason for that is because interstate freeways are so incredibly dangerous.
The death rate for interstate freeways looks pretty good, only because the population the death rate is measured among (adults in cars) includes none of the relevant vulnerable population. Because the relevant vulnerable population simply can't be found in any great numbers at that location. Because it's too dangerous.
Rich people are going to be fine anywhere. (Stockholm doesn’t get any increased mortality from the cold, no matter how cold it gets.) The relevant vulnerable population is poor people. Poor people simply can't be found in cold places because cold places kill poor people too reliably for a not-wealthy population to grow.
> The lowest recorded temperature in Kampala, Uganda was 12C (54F). Who’s dying from that?
Have you tried to live at 54F? Actually tried? It's really hard! That's why you don't have your thermostat set to 54F. It wouldn't kill *you*, because you're a wealthy First Worlder, but if you're so poor that survival isn't a given, "everything in life is harder" has a lot of knock-on effects.
When in Saudia, I had a long talk with a German organ-transplant-surgeon. He said the declared "causes" on "certificates of death" are a bad joke (at least in Germany): if one dies at home, a doc (usu. GP) takes a quick look and writes: sth. sth. heart-attack. Which thus ends up meaning: "no idea, really, but does not look like murder" (in hospitals they will usu. at least have a clue, what to suppose). "Cardiovascular" is the default diagnoses, without much if any value.
There might indeed be many, many more "flu-related"(as in "corona-related") deaths than the records show. Esp. among the frail.
Saudia (Kuwait): - death among "true" Saudis should not show much seasonal fluctuation - they spend 99% of the day in ac-cars, ac-houses, ac-offices, ac-malls. AC usu. put on max. power. (They may go out for a picnic in the cooler months, they do not use "crowded transport" all year). out I had to wear a jacket in office, it was just too cool without. South-Asian workers there (building!) at 50C in the scorching sun: sure, they should show higher mortality in summer. Statistics from this region need to be at least double-checked (90%+ of people in Qatar are not Kataris).
Last: DANKE! I wondered about this heat-cold-deaths for a long time, now I can wonder much more profoundly. - Why even with central heating a day in winter kills 40% more than a day in summer - yeah, one might think that is relevant enough to study till we know.
So basically the Winter-Death correlation is huge, but not empirically related to temperature itself. I suppose someone needs to come at it sideways by crunching data on non-temperature variables to try to tease out their separate effects. For example, randomly:
2. How does altitude affect the winter-death connection? For example, you could hold geographical region constant while comparing temperature fluctuation if you compared the winter death rates in tropical African areas with colder high-altitude locations nearby (does anyone live on Mt. Kilimanjaro?) Do high-altitude, low latitude death rates correlate more with geographical region or places with similar temperature fluctuation?
3. Do hours of light and dark separately correlate with death rates? Are there seasonal fluctuations in hormones, Vitamin D production, sleep patterns, etc. that could be explanatory?
If someone really cracks this extremely non-trivial issue you've identified it might be a Nobel-worthy event.
There are a number of comments speculating that different populations may have different genetic adaptations to environmental conditions.
No need to speculate.
I recommend this review: "The Genomics of Human Local Adaptation", Jasmin S. Rees et al, Trends in Genetics, June 2020.
There are lots of excellent references within the paper that people can then follow up on.
Here's the abstract:
"Modern humans inhabit a variety of environments and are exposed to a plethora of selective pressures, leading to multiple genetic adaptations to local environmental conditions. These include adaptations to climate, UV exposure, disease, diet, altitude, or cultural practice and have generated important genetic and phenotypic differences amongst populations.
In recent years, new methods to identify the genomic signatures of natural selection underlying these adaptations, combined with novel types of genetic data (e.g., ancient DNA), have provided unprecedented insights into the origin of adaptive alleles and the modes of adaptation. As a result, numerous instances of local adaptation have been identified in humans.
Here, we review the most exciting recent developments and discuss, in our view, the future of this field."
>But then why don’t we see any effect from excess winter heart attacks in very cold places like Stockholm or Siberia? Overall I’m not convinced of this one either.
Selection? This would be extremely interesting to study (genetically or epigenetically).
It's not the cold - it is the UV light that is missing in winter.
A whole host of physiological processes are dependent on UV light, vitamin D synthesis being the best known. But also nitrous oxide synthesis, lots of weird immunology and neurology are affected.
All the studies looking at excess winter deaths are the same as the ones looking at increased mortality from low vitamin D - they are measuring a surrogate for low UV exposure.
As a result, I expect global warming to be a net benefit as less clothing will being worn, hence elevated UV exposure.
Forgive me if this has been covered in the many, many comments below, but:
My understanding as to why flu is more prevalent in colder weather is that 1) sunlight kills germs, and there’s less sunlight (and people go outside less, which is perhaps the more important factor) in the winter, and 2) viruses don’t like humidity (for reasons I don’t quite understand). These at least seem to be the popular theories, and I would think that they at least deserve a mention, if only to dismiss them.
On a separate note, I’ve gone from “global warming will decrease cold deaths less than it will increase heat deaths” to “I’ve heard that that’s not true, and so now I don’t know,” to, now that I’ve read this article, “it looks like cold and heat deaths are mostly about human adaptation or lack thereof, so there’s no real way to tell what the effect will be—probably very little, but, as always, worse in poorer areas."
>The lowest recorded temperature in Kampala, Uganda was 12C (54F). Most years it doesn’t even get that low! Who’s dying from that?
Ok so it's clear you haven't been to Kampala in the winter, because 12C when it's usually >35 is absolutely freezing. The people in Kampala are certainly all wearing mittens and fur coats when it's 12C; I spent a couple of months in a similar place and if it reached 12C that was bad. Not only that, but 12C without heating at night is even worse. If you don't have super warm blankets and try to sleep in an unheated house as 12C you will certainly get sick. Add to that the fact that if it's 12C at night it might still be 35C in the day a few weeks later. The sudden temperature swings are what people say triggers the flu wave; not sure if true but certainly seemed plausible.
I know it's probably impossible to measure well, but whenever I see something like this, I always wish that we could get a measure of QALYs rather than deaths.
Because if it's like 'these terminally-ill bed-ridden 90+ year-olds are going to die from something in the next year or two, and it turned out to be becaus their hospice nurse was 20 minutes late because of snow on the road', then my reaction to that is very different from 'healthy people in the prime of their lives get freak heart attacks from constricted blood vessels when otherwise they would have lived another 50 healthy years'.
> I find this suspicious, and I wonder if there are a bunch of less obvious seasonal viruses going around causing deaths that don’t get recorded as “seasonal viruses”. Or: we know that sometimes people can get strokes and heart attacks as complications of the flu - maybe we don’t notice the flu, or coroners don’t record it, and it just gets marked as a stroke or heart attack.
I had exactly this discussion with my partner who is a doctor. I had been speculating that our increasing understanding of COVID complications like strokes, clotting, heart attacks, etc. likely indicates that there are all sorts of complications with other common illnesses that we never studied deeply enough noticed before, and so we may have underestimated those numbers for years. Comparing like vs. like against COVID will be a shifting game for years if this is true.
Unfortunately this will also probably be used as justification by both sides of the lockdown debate.
I think you are on to something with extreme weather, as it is experienced locally, being the culprit. We had a bad heat wave in Oregon recently and a lot of older people died. It was even worse in British Columbia.
It wasn't the old people who needed to be cared for by other people who died. The victims tended to be independent old people who lived alone. My mother is really old, but she grew up in the tropics and rolled her eyes at me when I gave her advice about how to keep cool. She was fine even without air conditioning.
It was pretty hot, but I doubt if comparable heat in the Deep South would have had the same impact. A lot of the harm of extreme weather is going to fall on frail people who don't know how to cope. A young, fit person can deal with stress that will kill an old person. It will suck for them, but they'll live. Old people don't have the same margin of error, and if they don't have the experience to deal with the weather event they are far more likely to die.
There are a lot of simple things that people do every day that are taken for granted, but in aggregate they matter a lot. I think many lives could be saved by educating people who have narrow margins for survival how to survive rare events.
As for winter being a problem in tropical countries... I'm not sure about the flu being the culprit. What's the weather like during winter? Does it rain more? Does it flood? I'm with you on the temperature not being the cause but correlating with something else going on.
That excess winter death graph you have is interesting. The Netherlands, Belgium and France are right next to each other, but their data points are very far apart. Half of Belgium is Dutch, the other half is French, so IDK what the hell is going on.
Can somebody explain what the "minimum monthly temperature" means in the plot? Because I'm from Portugal and I'm sure it gets well below 10C there in the Winter...
One possibility is that people choose to rest during periods of "aberrant" temperature (heat in the tropical regions, cold in the cold regions). While you are resting (sleeping, siesta, whatever) at home, you are LESS likely to die.
So, the actual effect may be that cold death rates in sub Saharan Africa are "normal" and heats results in lower than "norm" death dur to lack of exertion. The opposite with heat in the cold regions.
Maybe influenza (and other seasonal viruses) are cyclical by nature (evolution/mutation load in ARN viruses together with group immunity can lead to that, in a typical cyclic predator/prey dynamic), so a rather weak and local periodic signal (winter in the more densely populated regions for example) will act as a sychronizing clock to the inherently non-linear cyclical epidemy. This signal can be weak, with period variation, even skip a beat from time to time, while the response stay strong with a more stable period than the trigger...
This is also a postulated mechanism for global climate periodic variation (glaciation, oceanic cyclic oscillations), and quite a convincing argument on how relatively stable periodic phenomenon occurs seemingly out of nowhere...
Surely it's all the indirect reasons that are most accountable. From what I understand, 'crop yield down -> guy somewhat poorer -> more stressed and heart attack' would also get captured by their function.
- The estimations of the number of deaths due to Climate Change are dominated by deaths due to malaria and famines, both of which seem preventable by non-climate-related methods, i.e. better treatments for malaria (which are being worked on) and either some economic or humanitarian measures to mitigate the effects of localized droughts.
- Even if you consider the deaths from hypothermia alone (which are definitely cold-related -- it's there in the name), you'll end up with at the very least 50000 death per year, probably more, which is higher than the number of deaths from heat.
- That said, it is not clear how climate change will affect hypothermia, because deaths from it occur during unusual cold spells, and their frequency and severity may actually be increased due to climate change, because it increases the variance in weather events.
So there’s a clear hypothesis why warmer places have higher winter mortality; they get a similar variation in UV light, plus the warmth is good for bacterial and viral growth and survival.
One possible (partial) explanation for the unintuitive effects is that a lot of the investment/infrastructure that reduces weather-related mortality-- heating, air conditioning, social norms that reduce time spent outside in poor conditions-- aren't really about mortality. They're about enjoying life and being comfortable. So sure, warm places might invest more in AC and maybe won't invest in good insulation and back-up heating systems. And as a result, they'll be more susceptible to mortality to cold than heat. But they weren't trying to equate the marginal cost of mortality prevention across hot and cold days... they were trying to equate the marginal cost of *enjoying life*. Growing up in a cold climate, the first even remotely warm day of May, my parents would take my brother and I to the lake and we'd exhaust ourselves swimming in the frigid water. Later, in college, that same warm May day would be an occasion for excessive binge drinking on our outdoor couch. Beach-going and alcohol are probably bad for maximizing life expectancy, but certainly good for something.
1. Deaths in tropical EU are practically not seasonal. Below is a chart I made for covid tracking reasons for Overseas Territories of France, the gray line is the average of weekly deaths in 2016-19.
2. Most of the studies I have seen uses daily average temperature. Maximum and minimum may be more relevant. For example, without air conditioning a lot of people have trouble to have a good night’s sleep when the minimum is more than 24C.
3. Climate/weather is more than temperature: for example, weather fronts are known to have large health effects, and weather fronts can be seasonal. Also, wet bulb temperature can be very different from actual temperature.
4. There can be a lagged effect of cold/hot weather, with some kind of accumulated damage/depleted resources (vitamin D, other vitamins etc.). The post mentions it, but it can be even longer lasting than just the extreme weather spell (there could be a decline throughout winter).
5. The ultimate question is whether apart from seasonality, overall mortality is lower in places with “better” climate (this may be difficult to define). There are many confounding factors, income, smoking etc., but within the EU at least, there is some evidence that the further South a location is, the higher is life expectancy (there is data for NUTS2 regions). The Madrid region has the highest life expectancy amongst EU regions. Corsica, Caribbean islands of France are pretty well placed too. In the detailed data though, as far as I remember, this results mainly from lower cardiovascular and cancer deaths – it would be a very important area to study.
6. There is a large difference between life expectancy of US regions and EU regions (latter is typically higher), if anyone has studies that compare seasonality, please link it here (i.e. is it mainly excess winter deaths, or is it higher all year around).
> Why would cold places adapt so hard that they did better than warm places? I don’t know, but this is what everybody says.
> I still don’t really get why cold cities over-adapt and end up with even lower mortality than the warm ones.
(I'm confused by the overall picture too.)
That's probably because many of these adaptations are discrete, not continuous. There's a certain cost in turning the heating slightly up or down (which is continuous), but the main cost is setting up the infrastructure. If you have 80% of the pipes needed for central heating to work, you don't have 80% of the heating, you just get a plumbing mess.
Are we dismissing the idea that temperatures that seem moderate to you are highly uncomfortable for people born in a different area? -- so I imagine the people are adapted to that temperature, and they function less well in other areas. There's long term and short term adjustment -- apparently stuff like the number of sweat glands you have is calibrated based on how hot it is for your mother when you're in the womb; other stuff is multi-generational adjustment.
But anyways, just anecdotally, I know people from much colder climates and much hotter climates who self report as being less comfortable and less healthy whatever they do. Even if you cover up, you're still having to breathe in a lot of cold air all the time if you're from a culture where covering your face is weird (or maybe with covid, that taboo has been busted?); but it's self-reported so who knows.
Separate question: how do we deal with the issue that death is inevitable when looking at these numbers? I've always wondered about the fact that presumably above a certain age, when death is inevitably just around the corner and you only need to make a mistake -- if causes of death are zero sum: reducing the number of deaths from falling down the stairs has to be balanced by deaths from some other source, because it's inevitable -- modulo extending someone's life by a year. I guess this is why people focus on deaths to youngish people?
If you are a stranger in Florida on an epic hot / humid day you are surrounded by people who are experts in surviving that climate with the necessary infrastructure to survive. If you show up on a very rare epic cold day you surrounded by idiots who don't have a clue what to do.
> The lowest recorded temperature in Kampala, Uganda was 12C (54F). Most years it doesn’t even get that low! Who’s dying from that?
Try being in that temperature without proper clothes. I am pretty sure that it is enough.
I was sleeping in test 12 C with clothes for 16 C and it was miserable. I would not be surprised by frail person with clothes for 26 C dying.
And poor weather to that like rain or wind and lack of high quality tent and add illness/malnutrition on top of that. And I would be even less surprised.
Many years ago I remember (anecdote alert) that the radio news reported that missing persons were often found dead in the countryside, and to have died from 'exposure'.
It's quite possible that people who are warm in the day through activity, climate, or shelter nonethe less die of 'cold' or 'exposure' overnight because of the reduced activity and shelter even if the temperature is not absolutely cold in temperature terms. I imagine that people in Africa might find the nights lethally cool if there was no cloud cover or shelter.
In extremely poor regions of South America and Africa, it happens that people die in winter during sleep because they use charcoal for heating and get suffocated.
If HxNy were the only flu strain, we would approach herd immunity within several years, even through a cold winter. So the flu continues to mutate into different strains to evade immunity, and one of the major unmentioned factors here is this strain churn, means a (in reality, a set of dozens of) different strains circulates through populations each year. The consistent cyclicality of flu season is largely driven by strain churn, but that still doesn't explain the peak/trough and their correlation to seasons.
I'd speculate summer as the selection bottleneck in highly seasonal regions, and winter as the exponential part of infection S-curve of a novel infectious agent. So: it's summer is northern Eurasia, and the living is easy, except for the immuno-compromised. Which strain is best able to make it through the summer? This is largely driven by which strain does the immune system have the least memory of. And since the immuno-compromised are usually old, this is perfect for finding something most other people have never been exposed to either.
Now it's September, and the flu has faced a 99% mass extinction event - especially around the previous year's strain where R0 is approaching less than one. Whichever funky new (so old, it's new) strain was able to hang on and continue to infect is going to well poised to spread through the rest of the population. Through travel, hajj's, agrarian laborers etc, these selected for strains again move throughout the world causing another peak. Immunity to the new strain builds, and then we do the summer selection process all over again.
"We still don’t really understand why the flu is seasonal."
Is anyone looking into migratory bird patterns? I'm surprised that the Wiki article didn't even mention those as relevant.
Waterfowl like ducks are reservoirs for influenza strains and migratory birds are known to be important to influenza's evolution and spread.
"Virologic surveillance of apparently healthy birds has established that the waterfowl of the world are the natural reservoirs of all known influenza A viruses. The Anseriformes (waterfowl) and Charadriiformes (shorebirds and gulls) are the major reservoirs in which the 16 HA and nine NA subtypes are perpetuated"
A common chain of transmission is that a virus will spread from migratory birds to farm-birds like ducks to farm birds like chickens sometimes passing through pigs and finally to humans.
It seems notable that the % overall excess death ratio reported in the Zhao et al. study throws up the most extreme and counterintuitive results in areas where the study's data is very poor and the temperatures are very extreme. It looks like they only had daily time-series data on mortality for 43 countries and extrapolated their mortality rates for all other areas based on factors like GDP/capita and daily temperature ranges. Some areas in sub-Saharan Africa and central Asia have extrapolated excess death rates (for counterintuitive causes of death) as high as 20-25%, which is WILD, and these areas seem to correspond with a) a lack of daily time-series mortality data for that location b) low GDP/capita and c) extreme local temperatures. It's possible that these simply ARE the conditions under which extreme counterintuitive mortality rate increases occur, but it feels much more like a model being left to its own devices and getting a little wibbly around the edges when the data is spotty.
(It's also worth noting that the scales on the map of annual average heat related deaths in Fig. 3 look suspiciously data-crime-y, but that's more of a procedural quibble than a criticism of the article. I bring it up here because without paying attention to the scales of the graphs it looks deceptively like the rate of heat related deaths for Europe [where there data is good] is very high.)
I find myself mulling over whether there is any correlation between the average wealth of a culture, and the rate of deaths related to either extreme cold or extreme heat. But I also am trying to figure out how pre-industrial cultures and civilizations dealt with extreme weather.
Do we have good data for deaths due to extreme weather among the Dorset people, or Icelandic settlers, in Greenland 1000 years ago? Between the two groups of people, I would suspect that the Icelandic culture was slightly wealthier. Did this affect survival rates during the transition from Medieval Warm Period to Little Ice Age?
What about the Thule people, who replaced both groups in Greenland? Were they wealthier, or not?
If any of these three groups had a better ability to survive in climatic extremes, it was more a product of culturally-learned behavior than of genetics or economic success.
I suspect that this pattern shows up in many of the examples cited for deaths due to hypothermia during a cold snap in warm climates, or deaths due to heat stroke in a cold climate. If the problem hasn't shown up often enough to generate a cultural story of what not to do in that scenario, then the likelihood of a person choosing to do something foolish increases.
The wealth of a culture can put a layer of protection around a person. It can reduce the need for the transmission of cultural knowledge. In some cultures, it was the knowledge about how to keep warm sleeping on the ground. In other cultures, it was the knowledge about how to keep cool when the temperature stays hot all day and night for many weeks on end.
Sorry, I didn't read all the comments, and certainly someone else mentioned this - so apologies to them, but I think you're looking at this the wrong way. You finally touch on this at the end of the article, but you use the word "because" as it relates to death which I believe has distorted your thinking. People don't die "because" of the flu, the heat, the cold, etc. People die. (hard period). However people die * sooner than we might like * "because" of the heat, cold, etc. So, the only stat that makes sense and what you need to look at is Years of Life Lost (YLL), or better yet Years of Quality Life Lost. Deaths will go up short term during the cold and heat, but a careful analysis should (perhaps) look at the annual death rates and see if during a year with higher than average temperature in a region the annual death rate has increased. I'm not saying it's not a tragedy when a certain percentage of the population dies 6 months sooner than they normally might, but that doesn't have the same implication as "10% of all deaths are due to cold".
One problem with "hot cities have worse life expectancy" is that hot cities also have lower income and otherwise differ demographically.
If you look at North America and Europe, the most affluent countries are in the north, and the poorest are in the south. Moreover, further north in the US, there are generally fewer black people on average, and more Asians, and blacks have higher mortality rates than whites do while Asians have lower mortality rates and live longer.
Hawaii - a tropical state with very few black people, but enormous numbers of Asians - has the highest life expectancy of any state. California, which has a lot of Asians and Hispanics (both of which have above-white life expectancy in the US) has the second highest life expectancy, despite being a hotter state. Indeed, the US north/south cline is mostly because of the South, which is also extremely obese, which is likely another significant driver of the trend.
As such, this really seems likely to be a "richer places live longer" thing... which makes the trendline completely worthless. The rich places that are pretty hot - like Hong Kong and Singapore - have quite long life expectancy, and Australia, which is also a pretty hot country, also has a good life expectancy. These "abnormalities" are simply the result of there not being many developed regions in hotter areas of the world.
And with regards to mortality rate increasing over the 21st century, this is goin to happen regardless of global warming, because the population is getting older on average because people are having fewer kids. So it's kind of worthless to project that mortality rates are going to rise, because no matter what we do, they're going to go up simply because there will be a higher percentage of old people in the population, especially in developed countries.
Okay, simple correlation: more exposure to sunshine = higher serum Vitamin D3 levels. Countries that consume a lot of fish/fish oils will have consistently higher levels of Vitamin D3 during periods when the population has lower exposure to sunlight. Higher levels of Vitamin D3 provide higher levels of protection against diseases and blood clotting/strokes/heart attacks.
Lancet article says: https://www.thelancet.com/journals/lanplh/article/PIIS2542-5196(21)00081-4/fulltext tl;dr: "Globally, 5 083 173 deaths were associated with non-optimal temperatures per year, 9·43% of all deaths were cold-related and 0·91% were heat-related). ... Eastern Europe had the highest heat-related excess death rate and Sub-Saharan Africa had the highest cold-related excess death rate. ... From 2000–03 to 2016–19, the global cold-related excess death ratio changed by −0·51 percentage points and the global heat-related excess death ratio increased by 0·21 percentage points, leading to a net reduction in the overall ratio." - Cheers, global warming for saving millions from premature death this century! Ahrrg, "millions" - so it's just statistics ... :(
>the excess winter heart attacks, which are a direct effect of cold weather.
Keep in mind that influenza increases heart attack risk. https://www.nejm.org/doi/full/10.1056/NEJMoa1702090?query=featured_home
This is minor, but I think this part is backwards:
>Most people don’t clearly say that excess winter deaths are a combination of cold-related (from the flu) and season-related (from cardiovascular) deaths, even though something like this has to be true
Isn't the flu season related and cardiovascular deaths cold related?
I don't really think pointing to influenza or other diseases in Africa does much to explain the data. After all, that just pushes the question back one stage: why is it that these flu deaths are concentrated in the winter? If it's because they are more common when the temperature is lower than wouldn't that also support a causal story? You might try and say it's about the worldwide increase in flu during the winter but that doesn't work as the southern hemisphere has winter when we have summer.
I'm going to suggest a different explanation. Maybe it's all just about extremes of temperature being associated with unusual weather conditions which are more likely to lead to things like crop failures (and all the downstream badness including more wild animals dying leading to more opportunities for death). I have to think a bit more about it but the graphs above estimating MMT make me suspect that this is all mostly seeing some kind of mathematical artifact (e.g. that the more extreme the temperature is on a day the more likely it will be to occur during an unusual weather year).
> are a combination of cold-related (from the flu) and season-related (from cardiovascular)
Are these supposed to be swapped?
I believe that David D. Friedman has an explanation for "[w]hy would cold places adapt so hard that they did better than warm places?"
In short, I believe the explanation is that it does not make sense to invest in heat regulating equipment or insulation in temperate places (in his example, New Zealand), because they have high fixed costs. Accordingly, houses in New Zealand are very poorly heat regulated (and, although it does not get extremely cold in New Zealand, the houses are much colder than countries with more extreme temperatures). In contrast, to survive in certain places with more extreme temperatures, it makes sense to incur the fixed costs. Once those costs have been incurred (e.g., for insulation), the average cost of achieving the optimum temperature year round is low.
I seem to recall that David D Friedman had this written up somewhere, but I can no longer find it. Since I understand David reads this substack, hopefully he will be able to expand further (and apologies in advance for any incorrect summary).
Wait, no, isn't there a *really* simply explanation here. Generate some random data. It will always have some minimum mortality associated temperature. If you then call the increases in death relative to that MMT that occur at higher temperatures heat related and those at lower temperatures cold related you'll find alot of heat and cold related deaths.
I agree this doesn't quite explain the asymmetry between hot and cold temperatures but I'm going to guess it's something simple about the fact that plants are grown during the hottest part of the year leaving the coldest part of the year more time to do things like fight wars or when shortages are more likely to push people into lower immune activity or making more dangerous choices.
I have little to add aside from linking to my favorite flu-related paper, on the 9 conundrums of influenza
" (1) Why is influenza both seasonal and ubiquitous and where is the virus between epidemics? (2) Why are the epidemics so explosive?
(3) Why do they end so abruptly?
(4) What explains the frequent coincidental timing of epidemics in countries of similar latitude? (5) Why is the serial interval obscure?
(6) Why is the secondary attack rate so low?
(7) Why did epidemics in previous ages spread so rapidly, despite the lack of modern transport? (8) Why does experimental inoculation of seronegative humans fail to cause illness in all the volunteers?
(9) Why has influenza mortality of the aged not declined as their vaccination rates increased? "
The authors hypothesize Vitamin D levels and "Good infectors". Whole paper is worth a read though.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2279112/
It frustrates me a little that the messaging around covid at the moment is still "We don't know if it's seasonal", when it's been behaving exactly like a seasonal virus all this time.
I worry that the Northern Hemisphere is about to discover that even with a heavily vaccinated population, keeping Delta (or maybe Delta+) covid under control in the winter is a much harder job than keeping it under control in the summer.
As far as I understand it, the expectation of increased mortality at higher temperatures boils down to (no pun intended) the shape of the mortality curve at most cities. The rate of increase of mortality below the optimal temperature is gradual, while the rate of increase of mortality above the optimal temperature is steep. Assuming that the mortality vs temperature curve doesn't change over time (a big if), a given temperature increase causes a large increase in the heat-related mortality and a smaller decrease in the cold-related mortality.
Whatever the mechanism turns out to be, what a fascinatingly counter-intuitive pattern of data. I love this kind of stuff.
> One more thing: is all of this is mostly killing very frail people who are on the verge of death anyway?
A lot of people are asking the same question about Covid-19.
In winter people have fewer fresh fruits and vegetables to eat (especially outside the first world). They also get less vitamin D from sunlight. Worse nutritional status in the population could weaken immune systems and slightly increase the r-factor of any virus. Plus cold helps the virus survive longer outside the body, and incentivizes people to gather indoors. The r-factor of the flu hovers near 1, so those small changes can make it go supercritical or subcritical seasonally. That's my best guess as to why the flu is seasonal.
But in general warmer areas have a higher disease burden due to vectors that can't thrive in colder climates. Warming will likely expand the territory of malaria, and I don't know if anyone is factoring that into their calculation of warming deaths. But maybe that will be moot if someone invents a good vaccine or a clever way to kill the insect vector. There's too much unpredictable human action between the warming and the final consequences to have high confidence in any number of deaths.
A couple of weird thoughts:
-Presumably one way to die while hunting in Greenland involves ice not being as solid as you thought, which is more likely if it's warmer? Do Tibet and the Andes experience something similar with more avalanches or rock/mudslides?
-One group of people who are particularly vulnerable to the cold are the homeless. Is there a relation between homeless population and cold-weather deaths, and is this affected by things like emergency shelters that only open in unusually cold weather?
I find the human ability to adapt to different temperatures fascinating, and I'm not sure I understand it well enough to dismiss the idea that people are dying at 60 degrees F out of hand.
My brothers and I all grew up in a temperate, almost Mediterranean environment: rare to get as hot as 100, rare to get as cold as 25. As an adult I moved to a place where the typical winter temperature is around 0, and in summer it doesn't reach 90. He moved to Mexico.
He visited me once in summer: it was 75-80 degrees the whole time he was here, and he spent the whole trip in a long sleeve jacket with a puffy vest on top. Because he was cold! It certainly wasn't a put on, his internal thermometer had just shifted upwards while mine had shifted down. A couple years ago we had a heat wave where it hit 88 degrees for a week: we were all miserable with the heat, even though I would have been fine with 88 before I moved up here. My younger brother is planning on moving to Sudan and has visited there before, in a region where the typical summer temperature is in the high 90s, low 100s. While he was living in Texas someone who had lived in South Sudan for a few years came to visit and talk to him about moving to Sudan, and that guy also wore a long sleeve jacket and puffy vest his whole visit. In Texas. In summer. He was genuinely cold.
I don't know how the body does it, but if someone can be genuinely cold in Texas in summer because they're used to hotter, isn't it possible that person might die of cold if it hits 50 degrees?
No consideration of the possibility that all this weirdness has something to do with genetic differences between populations? Africans are adapted to one climate, Swedes another. You can speculate all day on what that means, but all we know is that genetics is probably conflating all of this somehow and we can’t know anything until we account for that.
Aren't suicides seasonal? A quick search gives me Wikipedia saying they're much higher in spring and summer, though it sounds like it's about the season and not the temperature. Is this effect too small to be important?
A quick bit of googling found that chilblains can show up at temperatures up to 16° C. No one is dying of hypothermia at that temperature, but that doesn't mean health can't be affected, especially if you don't have access to a source of artificial heat.
Could there be aspects of acclimation in addition to adaptation going on here?
My completely speculative take of the scatter plot you you show is that countries to the top-right, i.e. high-temperature high-death countries, look like they could have more homelessness than the ones on the bottom-left. Perhaps it is homeless and almost homelessness that is explaining part of the relation, but I doubt it is much.
I don't understand how the MMT chart for NYC (showing the highest mortality at high temperatures) fits with the NYT deaths-over-time chart (showing the most deaths in the winter). I didn't take the MMT charts to be some sort of adjusted-for-season death rate, it's just death rate vs temperature, right?
It appears that the answer to the question "will global warming cause fewer people to die from the cold?" is "no: it will in fact cause _more_ people to die from the cold".
This depends on whether the "death vs. temperature" distribution stays fixed as the distribution of temperatures moves up, but that naively seems unlikely to me given that "death vs. temperature" is already so highly variable across geography.
Also relevant: did the Grateful Dead prophesy in "New Speedway Boogie" that the end of the world would come with cold-related deaths in high temperatures?
> Now I don't know but I was told
> In the heat of the sun a man died of cold
> Do we keep on coming or stand and wait
> With the sun so dark and the hour so late?
More than half of all Americans die in an institutional setting: hospital, nursing home, or inpatient hospice. All home + road + other deaths combined are less than 50%. The temperature inside a hospital has very little correlation with outdoors temperature, yet we see this incredibly consistent temperature-mortality correlation throughout multiple US and world cities.
If there was a breakdown of temperature-mortality curves based on place of death, we'd have a fairly good idea of whether it has anything to do with temperature at all.
If the correlation was truly a direct causal effect (unusual temperature -> death) then we would see an extremely strong correlation for outdoors deaths, a moderate correlation for home deaths, and very little correlation for hospital deaths. On the other hand, if the correlation mostly reflects seasonal variations in infectious disease, risk taking behavior, diet, etc. then we would see very similar curves regardless of place of death, or even stronger mortality curves in hospice and nursing home settings where the populations have the highest susceptibility to infection.
Here's a well-documented example of heat-related excess deaths: Worst heatwave of my 18 years in Chicago was five days in July 1995, where the temperature peaked at 106 and humidity was very high. The heat caused partial power outages so air conditioners were off at times and even iceboxes lost their ice.
Out of a population between 2.5 and 3.0 million, an estimated 739 more Chicagoans died that week than was normal. From Wikipedia:
"Eric Klinenberg, author of the 2002 book Heat Wave: A Social Autopsy of Disaster in Chicago, has noted that the map of heat-related deaths in Chicago mirrors the map of poverty.[2][7] Most of the heat wave victims were the elderly poor living in the heart of the city, who either had no working air conditioning or could not afford to turn it on. Many older citizens were also hesitant to open windows and doors at night for fear of crime. Elderly women, who may have been more socially engaged, were less vulnerable than elderly men. By contrast, during the heat waves of the 1930s, many residents slept outside in the parks or along the shore of Lake Michigan."
The city government didn't do a good job of responding with cooling shelters or public service messages to check on your aged relatives, although after the disaster they improved their response notably in subsequent heat waves.
https://en.wikipedia.org/wiki/1995_Chicago_heat_wave
Who dies of 12C weather & why very cold cities have fewer cold-related deaths than hot countries in Sub-Saharan Africa has everything to do with the simple fact that cold places tend to be rich and hot places tend to be poor, and poor people in hot places have exactly one way of dealing with cold weather they aren't used to -- they build fires.
Remember, we are talking about people too poor to own sweaters, or boots, or woolens of any kind. Their only shoes are sandals. They live in huts with zero insulation, because they are made for air flow in hot weather. And they often sleep outside, with thin sheets to serve as blankets, if any.
Under these circumstances, 12C or even 15C or 18C is absolute torture, especially when your body is not used to it. I grew up in a tropical country and despite almost 20 years in the US I am still miserable at any temperature below about 18C (65F). And I own all the winter paraphernalia I need!
So what do you do when it's a bitterly cold 17C and you have no way to keep warm? You build a fire, and try to keep it going all night. And you have no actual fireplace, or chimney. I wonder how many of these winter deaths in hot countries are actually a consequence of fire.
Shoveling snow off your driveway is a stereotypical way for a man to trigger a fatal heart attack.
I have no idea, however, how big of an effect that is.
Climbers head to the Himalayas and the Andes to mountain climb in the summer and it's fairly dangerous. Not sure if an Everest avalanche tourist death in late spring might be counted as a Tibetan heat related death or not.
Death by hypothermia being more common in hotter climes actually makes a good deal of sense to me. Yes deserts are hot, but they also shed heat incredibly quickly once the sun goes down as anyone who's spent a fair bit of time in Africa, the Middle East, or even Utah can attest. Getting caught outside after dark without a blanket or warm clothing is a legitimate and widely recognized danger.
That said I don't see how that would translate to people dying of heat-stroke in Greenland. A rash of malfunctioning saunas maybe?
When we are talking about sub-Saharan Africa, what months are winter? Does the flu season actually correspond with the lowest-temperature months in all these places or does the fact that it's flu season in other populous parts of the world change that?
Not particularly happy with any of the studies either, or our ability to draw conclusions from them.
But one thing I found interesting was the global mortality rates with income-based adaptation (like more a/c) mentioned in Bressler. Logically, as people get richer, they can offset some of the heat-related deaths by investing in adaptation, and the higher emission mortality rate decreases from 6.2% to 4.2% when this effect is included (a not insignificant effect).
But one piece that is missing is many proposals for mitigating climate change (e.g. a carbon tax) have economic costs that will compound and lower global economic growth over time. If income-based adaptation to heat can have a significant impact to global mortality projections, how much of a decrease could the foregone income from lower growth rates have bought (across not just heat adaptation but all healthcare-related investments)? Isn’t it possible that the effects on mortality of having $10’s or $100’s of billions less of global GDP over a period of 60 years would swamp any direct change in the mortality rate from temperature changes like the ones forecasted?
This, of course, would say nothing about whether those costs or mortality benefits would be equitably distributed, but it’s a piece of the puzzle that is rarely pointed out in papers that seek to quantify specific costs of letting the temperature rise.
I suspect one reason why cold cities over-adapt is that some of the important ways cold is dealt with tend to be fairly binary. That is, you aren't really optimizing houses for a particular temperature, you're optimizing them for heat retention (within some bounds, of course, but it's not a very granular decision). You either have heating infrastructure or you don't (and if you do you either have laws and norms about making sure people get heating even if they can't really afford it or you don't). Sure there's more gradation at the personal level with things like various jackets and coats being appropriate for various temperatures, but at the level of construction and governance there are big, binary choices and as they get made they push you into being over-adapted.
Can someone ELI5 those graphs of mortality in cities? I don’t understand how the histogram of deaths relates to the curve.
Three comments. The first is a point already implicit in your discussion, but one that I think you missed earlier and many people still do. Heat mortality isn't just, probably isn't mainly, people going out in a heat wave and dropping dead. Cold mortality isn't just people freezing to death. Those are dramatic examples, but probably more important are the people who are made a little worse off by heat or by cold, a few of whom die sooner than they otherwise would.
The second is something that I noticed looking at the latest IPCC report and that they, I think, never mention. The effect on heat or cold-associated mortality depends on how much warmer climate change makes winters, how much hotter summers. The report gives projections for the change in how hot the hottest day of the year will be in various places with various amounts of global warming. It has a chart showing how cold the coldest day of the year will be in various places with various degrees of warming.
I looked at how much hotter the hottest day got in hot places and how much colder the colder day got in cold places. The answer was that the coldest day in cold places got two to three degrees warmer for every degree of global warming, the hottest day in hot places got about one degree warmer for every degree of global warming. Warming makes winters milder and summers hotter but, at least for the places I looked at, the former effect was two or three times stronger than the latter. The report never made that comparison, provided the necessary information in different places and contexts for warming and cooling.
Similarly, the report routinely said that climate change had both effects but paid attention almost entirely to the effect of hotter summers. That fits my general view of the report, that the authors honestly report their results but are looking for reasons why climate change makes things worse, not reason why it makes things better. If you don't look for something you are quite likely not to find it.
I was thinking in terms of temperature extremes and had not yet read your post, so it didn't occur to me to look at the effect of warming on cold extremes in hot countries or on hot extremes in cold. Looking at those, the pattern is less extreme, but the qualitative difference remains — in most but not all places, climate change raises minimum temperatures more than maximum. I find in the Summary for Policy Makers:
"Some mid-latitude and semi-arid regions, and the South American Monsoon region, are projected to see the highest increase in the temperature of the hottest days, at about 1.5 to 2 times the rate of global warming (high confidence). The Arctic is projected to experience the highest increase in the temperature of the coldest days, at about 3 times the rate of global warming (high confidence).
My third comment has to do with the various attempts to actually measure the mortality effects. None of them should be trusted, at least until you go over them carefully. If an honest and intelligent person solves a simple problem he is quite likely to get the right answer. The more complicated the problem is, the more his answer will reflect either what he expects to find or what he wants to find. For an example outside of climate issues, consider the history of measurements of the charge of the electron.
Kampala, Uganda not only never really gets cold, it also has practically no seasonal variation in temperature. If someone has actually calculated temperature-related excess deaths for it, that must be from random weather changes, rather than seasonal changes.
Given that Kampala or similar places likely have no heating at all, and little insulation, a cool temperature outside corresponds to cool temperature inside. If the relation between colder temperatures and heart attacks exists even at near-room-temperatures, it's plausible that there are more heart attacks in Kampala at relatively cooler temperatures.
Scott, how long does it take you to put together a post like this? Just finding and processing these disparate sources on this out-of-left-field topic is something. But you actually synthesize them into a meta-study, which you wrap head to toe in engaging prose. (Or are there some behind-the-scenes researchers or editors contributing to this production?)
Feature request: Provide subscribers an estimated Hours To Produce figure on your posts?
I don't know if this is supported by evidence at all, but I think it's one possible solution to the paradox: suppose that temperature-related deaths are, for whatever reason, extremely non-linear with temperature. For example, suppose that you get 90% of heat-related deaths between 95F and 100F and 90% of cold-related deaths between 60F and 50F. Then in the hottest countries, heat-related deaths might be spread so evenly through the year that you couldn't identify a relationship between hotter days and more deaths. Similarly for the coldest countries you couldn't identify the cold-related deaths.
But even if something like this was going on, I think it could only explain the very hottest and coldest countries - if the trend holds up when just looking at the countries in the middle, then I don't think this would explain anything. From eyeballing the graph it seems like the trend does hold for the middle countries.
> Everyone says that global warming will worsen mortality from heat. I’m a bit confused by this also
There's an asymmetry here that might be worth noting: when it's cold, you can usually put more clothes on to warm up. There is only so much you can take off when it's hot.
(I've always found that frustrating, because I'm increasingly incapacitated by temperatures beyond 75F.)
A possible explanation for the data in Bangkok and other tropical parts of the world - the "cold" season is not just winter, it is also the rainy season when the disease burden and mortality go up every year due to a whole host of diseases of which flu is just one of them. Examples of other illnesses include dengue fever and leptospirosis.
This is certainly the case in my home state in India, Kerala. Mortality goes up in the rainy season which is not cold by any measure. But the absence of sunlight, presence of stagnant water etc probably does as much damage as colder weather does elsewhere.
It is difficult to find many papers on this subject but a a review of "fevers" in Asia is https://www.sciencedirect.com/science/article/pii/S1198743X18302544. Random newspaper articles on the monsoon season and disease in Kerala - https://indianexpress.com/article/explained/fever-panic-in-kerala-numbers-and-the-reasons-4715870/ https://theprint.in/india/dengue-h1n1-leptospirosis-the-monsoon-challenges-kerala-faces-besides-coronavirus/433127/
I think these sorts of studies miss some huge confounding factors related to some of the details that excess death numbers just cannot get at. In Michigan, where I live, we get a few pretty severe hot days in the summer and a few pretty severe cold days in the winter. When it’s severely hot out, we have old people dying in un-air-conditioned homes, since many here still don’t have central air and many old people cheap out about putting in window units until it’s truly hot out, not to mention farmers and construction workers who have to work in the heat. On the other hand, we get fairly few direct freezing to deaths in the winter because everyone has heat and most people avoid activity when it’s that cold. We get far more winter deaths from icy roads or heavy snow or the heart attacks from shoveling snow than from the temperature per se. This is compounded by the fact that below about 0*F we tend not to get much snow, so much of the direct causes death decrease below a certain temperature.
I think this analogizes well to the pandemic, actually. Despite the lockdown orders here, and despite the number of people working from home, traffic deaths went up in 2020 vs 2019. Way more people took advantage of empty freeways and the state troopers explicitly saying that they weren’t going to interact with people early in the pandemic just to write tickets to do dumbass car racing at 120 mph on the freeway and wrapped their shiny Shelby 350s around a bridge abutment. Similarly, some of the stay at home prevented flu deaths, but increased, say, cancer deaths due to delayed diagnosis. These things are often deeply complex systems with complex causation and I see no reason why temperature related deaths would be different.
Does your metabolic rate vary over the year? Could that be relevant?
Here's the best paper I've seen on why flu is worse in the winter:
Seasonality of Respiratory Viral Infections, Miyu Moriyama, Walter J. Hugentobler, and Akiko Iwasaki, Annual Review of Virology 2020
A thought and an anecdote:
The thought is that I am surprised you didn't mention increased traffic fatalities as one of the possible contributors to excess cold deaths. Obviously less relevant in places that don't get snow/ice in the winter, but where I am from traffic accidents do go up considerably once the roads are covered with winter yuck.
The anecdote:
It probably doesn't shed any direct light on the human data, but when I was growing up my family saw a very clear pattern in seasonal mortality of our flock of pet chickens. We typically had around 20-25 at any given time, and most only live to 9-11 years (actually somewhat bimodal with a peak at 5-6 and the other around 10) so we got a fair number of data points, and deaths of 'old age' clustered around early winter and mid spring. The early winter makes sense, they had an insulated chicken coop with an electric water heater and an electric heater in the coop, but they were still essentially living outdoors and the cold is an extra source of stress on the oldest/frailest. But the odd thing was the spring peak, which was actually the higher of the two. it was before the summer heat came in, but still well into spring and we could never figure out what the stressor was when the weather was that mild except that it must have something to do with the change in temperature moreso than the absolute temperature, especially since the winter peak was well before the coldest part of the year.
Don't extreme temperatures cause mortality in a lot more ways than listed here? They just sort of generally take a toll and make you more likely to die if you're sick, heat makes people more violent, cold makes people less social, etc. In places that aren't super food-secure they cause famines.
Just so I've got a handle to work with the equal and opposite ideas of more cold deaths in hot places and hot deaths in cold places, I'm going to refer to them collectively as environmentally oppositional deaths (EODs). So my first thought was that the EODs might be caused by excessive environmental controls: setting the A/C too low in hot places and cranking the heater too high in cold places.
There's a meme in some places that the weather forecast is always wrong (statistics to the contrary notwithstanding). In places where this idea is pretty widespread, would people develop a habit of compensating for how wrong the forecast is? Would this lead to unexpected extremes, ones bad enough to up the number of EODs?
Anecdotally, recently a small cold front went through, so we turned the heater on for the first time this season to brace for it and to get the cobwebs out for the months ahead. Unfortunately we didn't know how small the front actually was, because in the middle of the night we were woken up by how hot it was. I checked the thermostat, and while the heater was set to only 70, the temp gauge said it was 77 in the house! That's 7 degrees of difference, and compared to the usual climate here, that was a rather mild night. If something like this happened in a place with more extreme temperatures, I can't imagine how bad the temperature differential might be from such a mistake, and how many EODs that might lead to.
Maybe I'm missing something obvious, but I thought the flu is seasonal because people spend more time inside in crammed spaces in winter.
I would like to see these numbers controlled for schools in session. I find it highly likely that many seasonal diseases are seasonal because schools are usually packed full of children who pass illnesses to one another, are often asymptomatic or lightly symptomatic, and then go home to their families who are more susceptible.
This feels like the kind of post where it might be worth just calling up someone in the field and asking them questions for 45 minutes. I know that has never traditionally been the format of this blog but it would probably be a shortcut to a lot of interesting stuff that hasn't been synthesised in any published papers yet. In my experience, not every scientist you email will want to talk to you, but a lot of them will.
One point which has not been stressed here at all is the role of humidity especially for feeling cold. The effort to keep up a certain temperature increases with humidity due to higher heat capacity and conductivity of wet air (20C in water is quite different than 20C in air). This effect should be expected to be higher in warmer regions where humidity is higher and the number of layers of clothes is less.
We have examined relationships between mortality and cold and hot weather effects in Hong Kong. Basically the cold weather effect on mortality is pronounced and is independent of influenza rates. Also almost all causes of death are affect (except for cancer and accidents) not just cardiovascular deaths:
https://ehjournal.biomedcentral.com/articles/10.1186/1476-069X-12-59
Hong Kong is a good place to test this as the weather during winters varies considerably. During some winters temperature rarely go below 15C while others have been characterized by long cold spells (by our standard a cold spell has temperatures < 15C). During those winters with colder temperatures we see a lot more excess mortality. So not seasonal (at least not here).
Seasons in the Andes are not like seasons elsewhere. Winter is sunny and dry, with blue skies; summers are damp, and it's cloudy, and not that hot. (There are also mudslides during the summer, but much of their damage is to lowland regions lying further downstream.) Yes, in winter, it's chilly in the early morning, or even mid-morning if you are in the shadow (and it's temperatures in the shadow that are usually recorded, no?), but there's plenty of radiant heat from the sun. Of course too much UV can also cause problems, but generally not immediately - you could get skin cancer or sight problems later on. I'd certainly say winter *feels* healthier (to me, and to anybody else who is somewhat affected by asthma/allergies), at least in the regions that Peruvians think of as having "moderate altitude" (< 3750m or so).
While we are at it: global warming affects much more than just ocean levels. Andean glaciers are melting rapidly. Momentarily, the effect is not entirely bad (more water! good harvest! ah, ok, mudslides, but those are partly further down), but in the medium to long run, it's bound to be pretty terrible - without glaciers and less rainfall, the entire region could become basically uninhabitable (or really uninhabitable, according to some projections).
I'd expect regions to adapt according to comfort, which might be more than is needed to not die. So from a perspective that's only about death rates, it looks like over-adaptation.
Accidents are the number 3 cause of death (in the US anyway), and it seems plausible that you’re more likely to have an accident when extreme conditions force you to do things differently than normal. Maybe?
Also, FWIW, if their model uses 0.5 degree latitude by 0.5 degree longitude squares, that means the equatorial squares are much larger than the polar “squares”, though I’m not sure that helps explain anything…
I don't have time to check this carefully right now, but keep in mind that car crashes occur more frequently during cold months. Northern countries have methods of dealing with slippery roads such as spreading sand or mandating use of snow tires on vehicles. I assume that warm countries do none of these things and instead get surprised when the occasional cold month hits them.
My personal experience is that the change in temperature or any environment is a challenge to the body. 16°C in October feels cold, the same temperature in April makes me thinking about wearing nothing but a t-shirt (and if you see people wearing t-shirt in April - that are tourist from scandinavia visiting Germany).
How does this effect sub-sahara africa? People are used to constant temperatures during their whole live, and they are not trained to handle changes. I know a man in Bujumbura, Burundi, who went to hospital in Nairobi, Kenia. He felt uncomfortable because it was too cold (and we are talking about 10°F colder temeratures).
So the environmental changes could be more challenging to people in areas with less seasonal differences.
Doesn't help with iceland though.
My first thought was variation in day length and natural immunity. But then I would've expected a clear trend with latitude.
Still feel like something like this must hold. Would love to see an investigation of the seasonal health of the immune system.
Some thoughts that I haven’t seen mentioned:
1) You don’t buy the idea of 12C being a dangerous temperature, but have you ever spent a significant period at that temperature in an uninsulated building/outside? It’s freezing!
2) That said, Kampala’s annual temperature curve is basically flat, with a daily mean of 22-23 C all year. The way the main paper fits functions on top of functions, it seems inevitable that trying to draw a signal out of a 1C range will result in nonsense.
3) Nepal/Tibet could be related to the the monsoon, which coincides with high temperatures.
4) Does this post on the harms of cold have anything to do with your time in England?
I wonder whether the variability of temperature could play a role. That is a sudden heat wave or cold snap is worse for mortality than if it is always pretty cold or pretty warm. The nordic countries that have low winter excess mortality also have pretty stable climates. Iceland which had no winter excess death has a really low temperature variability (at least in the populated parts). Reykjavik has a daily mean of 0.7C in January and 11.6 in July and record cold of -20C. Nome in Alaska is at the same latitude and has a daily mean in January of -15C and record low of -54C.
A stylized model:
- R-nought for the flu gets above 1.0 in the temperate northern part of the world in, say, November-March and in the temperate southern part of the world (e.g., Buenos Aires, Melbourne) in May-September.
- People from the temperate world travel to the equatorial world more or less year round.
- Temperate people are more likely to bring flu with them in their homeland's winter and infect equatorial people they are visiting.
- There are vastly more people living in the temperate north than the temperate south.
Prediction: More equatorial people get flu in the Northern winter than in the Southern winter.
Is that true?
>very cold places like Stockholm or Siberia
Stockholm is actually not very cold. The average minimum for January is -3, same as New York, as compared to -21 in Novosibirsk. Still, it's cold enough that I'm surprised not to see any mention of the lives lost to slipping and falling on ice/snow (I think about half a percent of deaths), or the QALYs lost to injuries from slipping and also from the fear of slipping and the isolation brought by such fear (among the elderly).
Best scientific treatment I have seen so far on variations in temperature-deaths, and a nice open-ended discussion of possible implications of global warming.
Scott asks the question: Is it reasonable to assume people in cold climates over-adapt to the cold, relative to people in the South? (quote: "Why would cold places adapt so hard that they did better than warm places?")
I think a theory can be formulated. At least I have got one, based on living in the North of Europe and sometimes travelling to the South of Europe to escape winter – only to find myself almost freezing to death in some rented house in the South. (Ok, n=1, but wait for the theory)
Here is the theory: People in the North know that when winter comes and it gets cold, it stays cold for a long time. You cannot wait it out. So you have to put in the money to get central heating and those triple-glassed windows.
While people in the South know that when it gets cold, it usually does not stay cold for very long. If you brace yourself, the cold spell is usually over in three weeks max. You can brace yourself to live through three weeks of cold, but not four months. So you do not adapt at all.
Plus, to some extent people in the South must do the opposite: They adapt their houses to the often very warm summers. That is why I have never frozen more than in the South. Old stone-built country houses in particular (where old people often live), are built to keep the heat out in summer. Which makes the houses ice boxes in winter.
…for US people, a similar logic is captured by Mark Twain’s dry observation: “The coldest winter I ever lived was a summer in San Francisco.”
Finally getting to the testable hypothesis: If I am right that people in the South sit out the cold while people in the North adapt to the cold, we should get excess cold deaths in the South, but only in years with unusually long Southern winters; i.e. when the presumption that “the cold will pass” is not borne out. Scott’s information that cold deaths usually take place 14+ days after the cold spell starts, fits with this assumption.
To test this hypothesis we would need data not only on winter temperatures in different countries and across time, but also variations in how long the winters last. Cold deaths in the South should peak in years where winters surprise everybody by being long.
Finally, a bit of travel advice to ACT readers: Be careful if you live in the North and are tempted to rent one of those picturesque and suspiciously cheap old rural stone cottages in the South to escape your own winter! Speaking from bitter experience….
Confounding this is the fact that Scandinavian countries are not only prepared for cold weather, they do so in rather safe ways. Electrical or natural gas heating, or when wood is burned it is in airtight stoves with well-maintained flues. Here in Nova Scotia house fires and flue fires are common winter occurrences, but we can't afford to do things as well as the Scandinavians. But consider the case of sub-Saharan Africa: most cooking and heating is done over indoor open wood fires in rural areas. Even in cities the electricity supply is unreliable. Open fires mean increased COPD from breathing smoke, and that in turn means respiratory infections are likely to be more dangerous or even lethal. My wife started an orphanage for AIDS affected or AIDS orphaned kids in Kenya, and goes there yearly. She notices how they feel the cold - even when it seems hot to her they will put on coats as 20ºC seems bloody cold to them. So more wood gets burned. More risk of fires, and more respiratory infections from huddling indoors, and those infections will be more deadly in lungs that have been inhaling woodsmoke. Add to that the immunosuppression and general weakness from endemic TB, malaria and AIDS, and you can see why deaths skyrocket in the cold season. One thing we have done is to encourage the use of rocket stoves, which burn less wood (in short supply) and produce far less smoke. There is even a charity dedicated to encouraging their use - see https://www.aidafrica.net/rocket_stoves/
I'm taking the liberty of posting before reading all the comments. If lack of sunlight is a factor in winter deaths, then there should be a weaker winter death effect closer to the equator, even allowing for warmer temperatures.
If excess mortality is caused by temperatures outside the usual range, then moving the range up isn't going to lead to fewer deaths from cold.
For reasons I'm not going into, I live in Philadelphia without air conditioning. This gives me a different understanding of the effects of challenging weather than a lot of other people seem to have.
The high and low temperatures only give a modest amount of information. For *how* *long* was the temperature at or near the high? What were the lows like-- how much of a chance does the house have to cool off at night?
The worst summer weather I experienced was in Philadelphia in 1995. Two weeks of high of 110F and low of 85F, with high humidity. The air felt like it was so heavy it was hard to breathe.
Incidentally, the past three summers here have been relatively tolerable. Previous, the humidity was always pretty high, and I thought that it was inevitable because I'm living between two rivers. That theory is wrong-- the past summers have been at least as hot as the usual (highest temperatures in the 90Fs), but with moderate humidity. I have no idea what's going on.
Brilliant critical thinking.
From experience living in a multicultural family, I believe the over-adaptation to cold is true.
The (simplistic) rational is as follows:
- If you do not wear the appropriate clothing in mild European climate in winter, you might catch a cold. Big deal. People end up wearing unappropriate clothing out of laziness, wanting to look cool/strong (teenagers), and eventually habit.
- If you do not wear the appropriate clothing in Russian winter, you... die. Hence people are much more careful, and the intensity of this effect is non linear.
Slightly counter-intuitive, probably controversial, but all my personal data points support the hypothesis so far.
"You can see further debate between these groups here and here" - Both those links are the same.
I haven't read the papers, but does all of this relate to natural deaths only? Because I would imagine there to be a pretty strong link between suicide, car accidents, falling etc. with the cold (and thus dark) season. Sure, these don't make up the lion's share of deaths, but they surely play a role.
It's really hard to hypothesize about causes without more info, like:
- Separate deaths from transmissible diseases
- Separate deaths from exposure itself (i.e. "freezing to death")
- Attempt to account for "when people spend more time indoors" - this probably varies a lot by region, as some regions consider it "too cold" at different times than other regions. It's not settled fact that flu spikes in winter for ventilation-related reasons, but it's at least part of the equation. Related interesting question... when it's way too hot and everyone stays inside, does that lead to more disease transmission?
Thanks. I realize people are quite confused about this; someone even asks if hot places have winter. But I want to remark at least three main issues with this whole analysis that make me very suspicious about cross-country comparisons regarding deaths, temperatures and seasons:
1) CONFOUNDERS: distinguishing the “temperature factor” and “winter factor” is harder than we think, especially if what you want to measure is the impact of climate on health. It’s not just that there are too many confounders, it’s hard to define what is a confounder and what is causally relevant. For instance, winter is the dry season in Brazil: prices and allergies (because of dust) spike; global warming will likely make this worse. On the other hand, in higher latitudes, you have way less sunlight and significant behavioral changes; global warming may or may not help with that.
2) ADAPTATION: I wonder if physiological adaptation is underestimated. Acclimatization takes a while to be optimal – think about adaptation to changes in altitude; so, gradual transitions between temperatures should be optimal. But in tropical climates, you don’t have that: living in Sao Paulo, you can have 30ºC on a hot dry winter day, followed by a cold or hypothermia with 15ºC on the following rainy evening.
3) VARIANCE and MEASUREMENT: notice that some of the linked papers (those I checked, AT LEAST) used data on the average temperatures (usually the mean between the max-min on the same day). Not only this neglects wet-bulb temperature and windchill factor, it also equates a wet day with min of 15ºC and max of 35ºC (I hate those days) with a pleasant dry day ranging around 25ºC.
I wonder how the results would look when compared with seasonal temperature variability, as opposed to how hot or cold it gets on an absolute scale? Humans seem to benefit from a certain amount of variance, so maybe people who live in places where the annual temperature is between -10F and 60F are better adapted to deal with general physical stressors than people who live in places where the annual temperature is between 70F and 90F.
"I can’t really find anyone taking this seriously and saying that, as colder cities get warmer, their heat-related mortality will decrease."
Shouldn't that be "as warmer cities get warmer, their heat-related mortality will decrease"?
1. Let's say someone had a heart attack/blood clot because of a cold day. You'd expect to see increased mortality about a week or so later, because, while some people would just drop dead, others would go to the hospital and die there. A group looked a weather variables and incidence of DVT (blood clots) and found that around 9-10 days after a rainy day, or a windy day, or a day with low atmospheric pressure (more on that below), there was an increase in blood clots about a week later (source: https://pubmed.ncbi.nlm.nih.gov/19806252/#affiliation-1). It seems more plausible that these effects are mediated by inactivity than the effects of weather on our physiology.
2. Hawaii has VERY little variability in seasonal temperature (coldest month with a high of 80F, hottest with a high of 88F), but has about the same seasonality to respiratory infection and cardiovascular disease as other places with more variable temperatures (source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC28593/pdf/1946.pdf). Please click through and look at how smooth the temperature curve is while the respiratory infection and cardiovascular disease curves whip up and down every year. It just does not seem biologically plausible that temperature effects on physiology could account for such a significant amount of variation. Another way to say this; I don't think increased blood viscosity or peripheral vasoconstriction due to *slightly* colder weather could be causing increased cardiovascular mortality in Hawaii.
3. Inactivity is high associated with all cause mortality (https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2783711) though it's tough to determine causality since maybe people who are sick for other reasons move around less rather than moving being protective (though it does seem that a preponderance of evidence suggest that, all things being equal, not moving around much is bad for you-if anyone thinks there's good evidence to the contrary please let me know).
4. Re: association between low barometric pressure and blood clots I brought up in (1). I think even a short period of inactivity (I'm talking a few hours) likely significantly (but slightly) increases your risk of death in the short term. Case in point, physicians are trained to ask if you've recently taken a long flight when you come in with a blood clot. The reason is that the way blood returns from the legs back to the heart to get recirculated is by being squeezed by the leg muscles during normal activity. When you sit in a cramped airplane for a transatlantic flight, you might sit more or less perfectly still for >6 hours. Blood that's not moving is MUCH more likely to clot, and so you can get a blood clot.
The authors of the weather vs. clots study noted the strongest association between low atmospheric pressure and incident blood clots. I interpret that to mean that days with low atmospheric pressure (overcast, windy, rainy) correspond to lazy, inactive days at home. They wonder if there's a link between the low cabin pressures in airplanes and blood clots, in addition to the activity. Not sure how you would tease this apart.
I don't understand the definition of "cold-related death". Is it strictly death from hypothermia ? Is it death from seasonal illnesses, which are caused by the cold ? How far up the chain of cause and effect are we going to follow ? If a person is driving his car to work one day, hits a patch of black ice, spins out of control, and plows full-speed into a pedestrian, then did that pedestrian "die from cold" ?
Having lived in both extremes, some thoughts.
First, the causes of death. Heat-related causes of death are generally pretty direct; dehydration and heat stroke. They also predominantly hit the medically frail, but will also hit those with less experience with heat worse; as somebody who has lived in one of the hottest places in the country, I recognize the symptoms of heat exhaustion, and immediately rectify the situation. Somebody without experience with heat might not notice their heat exhaustion until they're too mentally addled to actually do anything about it.
Cold-related causes of death include both direct and indirect causes, however. For direct, there is hypothermia and exposure, which I think will predominantly affect the medically frail. But there are also cold-related accidents (slips/falls and traffic incidents), and also being snowed in, which can cause people to die of apparently unrelated accidents (bleeding out while waiting for an ambulance after a kitchen accident). These can be mitigated to a significant extent by appropriate local investment (snowplows, salting and sanding roads), but this is only done if it makes sense to make that investment.
For the indirect cold-related deaths, I think are notable in that they are not as limited to the medically frail. I'd hazard a guess that the average cold-related death costs far more QALYs than the average heat-related death.
Re: heart attack deaths, the paper you linked seems to be about blood thickening below a specific temperature rather than relative to local baseline. So maybe places like Stockholm are cold enough year round that people's blood isn't much thicker in the winter than it is the rest of the year?
It seems to me that the explanation about vulnerable (near death) populations is the most probable. It explains the lag time between cold weather and deaths (they get sick first) and also the tendency to be opposite in cold verses warm locations. A location that's unusually warm may help stave off a person getting sick, but a 10-20 degree temperature drop, even if the resulting temperature is well above what's needed for survival, would be enough to take their already frail body to a place where death is much more likely. In a truly cold place, that person would have gotten sick and died earlier (general death statistics regardless of temperature), or have been placed in a location where temperature differences are less of an issue - i.e. the insulation discussion, where Swedes are used to being cold and better prepare their populations for it.
In this theory, it's not acute cold that causes death, but instead lower temperatures that result in sickness and then death. Heat deaths, on the other hand, tend to be more sudden and directly related to high levels of heat, but would affect similar populations. Heat deaths come from heat stroke and other direct effects, rather than opening a person up to sickness.
Did you consider traffic fatalities in the winter? Anecdotally and from basically everybody I've spoken to, winters are more dangerous for driving due to snow, slush, wetter conditions, overcast etc.
> See also this paper, which is the closest thing to a useful summary by people with a smidgeon of curiosity that I could find in this space.
Clicking on the "this paper" link, I just see "AccessDeniedAccess denied"
It’s kind of fun to figure out where in the world commenters are sitting at their keyboards.
Unless they make an explicit mention of their location it’s enjoyable to see what can be inferred by their units of measure, local season mentioned, acronyms used or distinctive spelling of English words.
I am amazed by the global reach of ACX. Western Hemisphere and Eastern. Northern and Southern.
Our host has touched on how his readership has spread since his - I’m searching for neutral terminology here - let’s just call it interaction with the NYT.
No doubt it was traumatic at the time but the result sure seems like a long term net positive.
Linsey Marr recommended keeping air humid as a defense against covid but it depends on the virus for whether it prefers dry vs humid conditions. https://www.nytimes.com/2021/10/19/opinion/covid-flu-air-transmission.html
https://journals.asm.org/doi/10.1128/mSphere.00552-19
I'm wondering if that's a missing factor here. Is it less about the temperature and more about the humidity and whether it's raining? I'd be curious to see what mortality is like during rainy vs sunny periods, since that seems to correlate with temperature and could resolve the confusion about why the temperature differences for when mortality starts going up are so big from place to place.
I can't cache this out in detail, but I wonder if the odd global MMT results are partly just statistical artifacts. Like, sometimes the tails of distributions are the weirdest, least-normal parts (so maybe hottest and coldest places will break the model), and grid squares with smaller populations will have higher variance (e.g., Greenland must have a small population; thinking of that Andrew Gelman county-level rates of stomach cancer example).
I once treated someone for the beginning symptoms of frostbite in 60°F. I was so surprised I checked her several times before bringing her in and beginning treatment.
"I find this hard to analyze because I still don’t really get why cold cities over-adapt and end up with even lower mortality than the warm ones."
Just a theory. But because cold cities *know they are cold*? Whereas in warm cities, any increase in death might either not be particularly noticed, or not attributed to the temperature - because that possibility simply won't enter citizens' or policymaker's minds. After all, they're not cold cities!
Put another way, 'cold-related deaths' are simply more salient in cities that are already cold.
"I think the idea is something like if an extreme weather event kills lots of people one year, the next year extreme weather events will kill fewer people than normal, because a lot of the vulnerable people are already dead."
I wonder if there is evidence for this from, say, bad flu seasons - or indeed covid.
Extremely low confidence explanation for some of the weirder data:
Perhaps the human body, over long periods of time, adapts to given temperature ranges? Eg, someone from Uganda might find 80 degrees to be uncomfortably cold, with some of the associated dangers, as it’s on the low end of what their body has experienced. I don’t know enough to propose any mechanisms for this, but it seems like the sort of thing biological systems would cook up.
Anecdotally, I’ve known transplants from Florida to NYC who complain bitterly about temperatures that a local person would find quite comfy (~70 degrees).
On Tibet, Greenland, etc:
Your central source (Zhao et al) didn’t collect data on mortality in the places you’re most curious about -- Tibet, Greenland, central Africa, etc. They collected data on mortality in 43 countries (see fig. 1 -- it’s mostly high-income or middle-income countries) and used that to train a model that predicts the temperature-mortality function based on “meta-predictors” like GDP/capita and Köppen–Geiger climate classification. They didn’t look at any mortality data on Greenland -- they just look at the meta-predictors for Greenland, and use that to predict the temperature-mortality function for Greenland. They use that, plus Greenland’s population and temperature history, to guess how many heat-related and cold-related deaths it has. So the lack of curiosity about Greenland isn’t because they’re ignoring a strange real-world phenomenon -- it’s because they’re ignoring the strange behavior of their model at the edges of its distribution.
Note that Tibet, Greenland, and the Andes are all in the same Köppen–Geiger climate classification -- “ET” on the Wikipedia map. It seems likely that the training data included some Andean location with weirdly high mortality sensitivity to warm temperatures, and the paper’s model generalized from that to the few other populated areas with climate classification ET. Maybe that was a good generalization! Maybe whatever is causing high sensitivity to warm temperatures in the Andes is also true in Greenland. But the paper doesn't have Greenland mortality data to test that.
Don't deserts actually cool down really quickly?
https://www.livescience.com/why-do-deserts-get-cold-at-night.html
Exposure to cold temperatures has been shown to encourage fat loss and possibly help with diabetes. There are multiple mechanisms: other than simple thermodynamics, the human body adapts to cold temperatures by producing brown fat, which consumes calories to produce more heat in order to maintain body temperature.
This could explain why people in colder climates seem to be doing better overall: they're losing more fat naturally and improving their BMIs.
This link is a decent starting point, if you want to know more you should search for Ray Cronise (a former NASA scientist) and Tim Ferriss, a health and fitness author. They were among the first to popularize this effect AFAIK.
https://www.theatlantic.com/magazine/archive/2015/01/does-global-warming-make-me-look-fat/383509/
Maybe the next survey should have a question about preferred temperature ranges.
Scott, you spend a lot of this post discussing whether seasonal effects (rather than temperature effects) are driving the cold-weather deaths. But I think the paper is trying to control for seasonal mortality effects, and just focus on the excess mortality (excess relative to seasonal trends and other trends) associated with cold (or hot) days.
“...in the first stage, the temperature–mortality association for each of the 750 locations was estimated by use of a quasi-Poisson regression with a distributed lag non-linear model… where… ns is the natural cubic spline for time with eight df per year to control for long-term trends and seasonality”
They might do a bad job controlling for seasonality! But I would be very surprised if the cold-weather mortality they observe is mostly seasonal.
I’ve dug into this literature for a previous project. Despite the model’s strange behavior in low-population areas, my sense is that it’s probably doing a decent job estimating the temperature-mortality relationship in rich and middle-income countries. But if you want to use any of this to make inferences about the mortality cost of climate change, you need to reckon with a few other details:
The paper’s training data didn’t include any low-income countries. (See my comment on Tibet and Greenland, for a discussion of how they only train their model on a few countries.) The closest they get is the Philippines, a lower-middle-income country. (This is a welcome addition -- previous papers in this literature, like that from the Climate Impacts Lab at Chicago, only used upper-middle income countries like China and Brazil.) From what little data we have, it seems like infant mortality is much more sensitive to high temperatures in low-income countries. (See https://www.nber.org/papers/w24870. This makes sense: if you can afford any climate control -- a swamp cooler, a neighbor’s cellar -- you use it to protect infants on a hot day. So infant mortality is a lot less sensitive to heat in lower-middle income countries than low-income countries.) So, if you use this paper to estimate the effects of warmer temperatures on mortality, you’re going to miss a lot of infant deaths in low-income countries.
The papers you’re citing combine deaths across all ages. But the excess deaths on cold days are concentrated among the elderly, whereas infants disproportionately die on hot days. (You can get this result by playing with the data from the appendices of this paper: https://www.nber.org/papers/w27599) If you care more about the death of an infant than an elderly person, then this pattern will significantly increase the net mortality costs of warmer temperatures.
When economists try to turn these temperature-mortality functions into a “mortality cost of carbon”, they often assume perfect adaptation -- i.e. if temperatures in Delhi start to look like Kuwait City, well then everyone in Delhi will live like people in Kuwait do. Never mind that they may not be able to afford the air conditioning that makes Kuwait livable.
And then of course, none of this captures the mortality cost of stuff like climate-induced migration. Desertification of the Sahel, flooding in Bangladesh -- those are going to drive migration and conflict, and those mortality costs will be significant too.
"Why would cold places adapt so hard that they did better than warm places? I don’t know, but this is what everybody says."
Adaptations aren't continuous, they're discrete - e.g. if you already have a heating system, if it gets extra cold you can turn the heat up a little more, but if you have no heating system you will die.
> When you’re skeptical of complicated models, sometimes it helps to go back to the rawest data you can find. So here’s a graph of mortality rates in New York City over time.
But that's not the rawest data you can find. The rawest data is the number of people in New York City before checking what rate they're dying.
> If growth mindset was so great, you would expect fixed mindset people at Stanford to be as rare as, say, people with less than 100 IQ are at Stanford. Given that you will search in vain for the latter but have no trouble finding a bunch of the former for your study on how great growth mindset is, it sure looks like IQ is useful but growth mindset isn’t.
But I would drift one degree away from the rawest of data, because there's an elephant in the room: wealth. You talk about "cultural adaptation", but a lot of "cultural adaptation" is pretty obviously only posssible with large amounts of wealth.
> The worse your climate, the more likely you are to have good central heating.
Good luck having good central heating without wealth.
> Stockholm doesn’t get any increased mortality from the cold, no matter how cold it gets. Plausibly that’s because they’ve organized their lives and built environment around surviving cold winters.
There are a lot of people in Stockholm. But Stockholm is very wealthy. If Stockholm were not so wealthy, they would not be able to sustain so many people in such a hostile environment.
> I’m not entirely convinced by this story. Shouldn’t this mean that everywhere has the same level of excess death from the cold? Why would cold places adapt so hard that they did better than warm places? I don’t know, but this is what everybody says.
Cold places adapt better to everything. And yes, cold places really do adapt so hard that they do better than warm places. And the reason for that is because having a large enough population to be studied, in a cold place, is very very very strongly correlated with wealth. Cold places, or rather, the people *in* cold places, are wealthy, and wealthy people adapt better to any environment.
And why are large populations in cold places necessarily so wealthy?
There are places on Earth that reached large populations despite lacking great wealth. All such locations have one thing in common: they are warm.
This patterns *jumps* out of the data. You will search in vain for cold regions that reached large populations before acquiring large amounts of wealth, but warm regions have no such difficulty.
The one thing we can say a priori about the winter death rate in New York is that it can't possibly be very bad, because if it was, then there wouldn't be so many people in New York.
Which is a more dangerous location for children to play: a backyard swimming pool, or an interstate freeway? Well, many children die each year playing in swimming pools, and very few playing on interstate freeways. Therefore swimming pools are more dangerous. Do you see the obvious problem with this logic? The reason there aren't so many children dying while playing on interstate freeways is because there aren't so many children playing on interstate freeways. And the reason for that is because interstate freeways are so incredibly dangerous.
The death rate for interstate freeways looks pretty good, only because the population the death rate is measured among (adults in cars) includes none of the relevant vulnerable population. Because the relevant vulnerable population simply can't be found in any great numbers at that location. Because it's too dangerous.
Rich people are going to be fine anywhere. (Stockholm doesn’t get any increased mortality from the cold, no matter how cold it gets.) The relevant vulnerable population is poor people. Poor people simply can't be found in cold places because cold places kill poor people too reliably for a not-wealthy population to grow.
> The lowest recorded temperature in Kampala, Uganda was 12C (54F). Who’s dying from that?
Have you tried to live at 54F? Actually tried? It's really hard! That's why you don't have your thermostat set to 54F. It wouldn't kill *you*, because you're a wealthy First Worlder, but if you're so poor that survival isn't a given, "everything in life is harder" has a lot of knock-on effects.
When in Saudia, I had a long talk with a German organ-transplant-surgeon. He said the declared "causes" on "certificates of death" are a bad joke (at least in Germany): if one dies at home, a doc (usu. GP) takes a quick look and writes: sth. sth. heart-attack. Which thus ends up meaning: "no idea, really, but does not look like murder" (in hospitals they will usu. at least have a clue, what to suppose). "Cardiovascular" is the default diagnoses, without much if any value.
There might indeed be many, many more "flu-related"(as in "corona-related") deaths than the records show. Esp. among the frail.
Saudia (Kuwait): - death among "true" Saudis should not show much seasonal fluctuation - they spend 99% of the day in ac-cars, ac-houses, ac-offices, ac-malls. AC usu. put on max. power. (They may go out for a picnic in the cooler months, they do not use "crowded transport" all year). out I had to wear a jacket in office, it was just too cool without. South-Asian workers there (building!) at 50C in the scorching sun: sure, they should show higher mortality in summer. Statistics from this region need to be at least double-checked (90%+ of people in Qatar are not Kataris).
Last: DANKE! I wondered about this heat-cold-deaths for a long time, now I can wonder much more profoundly. - Why even with central heating a day in winter kills 40% more than a day in summer - yeah, one might think that is relevant enough to study till we know.
So basically the Winter-Death correlation is huge, but not empirically related to temperature itself. I suppose someone needs to come at it sideways by crunching data on non-temperature variables to try to tease out their separate effects. For example, randomly:
1. Does the winter-death phenomenon exists even in, say, Quito, Peru which is on the equator and literally has the same temperature and sunlight all year round. https://weather-and-climate.com/average-monthly-Rainfall-Temperature-Sunshine,Quito,Ecuador If Winter-Death exists in Quito, what are the categories of excess deaths that increase in Winter?
2. How does altitude affect the winter-death connection? For example, you could hold geographical region constant while comparing temperature fluctuation if you compared the winter death rates in tropical African areas with colder high-altitude locations nearby (does anyone live on Mt. Kilimanjaro?) Do high-altitude, low latitude death rates correlate more with geographical region or places with similar temperature fluctuation?
3. Do hours of light and dark separately correlate with death rates? Are there seasonal fluctuations in hormones, Vitamin D production, sleep patterns, etc. that could be explanatory?
If someone really cracks this extremely non-trivial issue you've identified it might be a Nobel-worthy event.
There are a number of comments speculating that different populations may have different genetic adaptations to environmental conditions.
No need to speculate.
I recommend this review: "The Genomics of Human Local Adaptation", Jasmin S. Rees et al, Trends in Genetics, June 2020.
There are lots of excellent references within the paper that people can then follow up on.
Here's the abstract:
"Modern humans inhabit a variety of environments and are exposed to a plethora of selective pressures, leading to multiple genetic adaptations to local environmental conditions. These include adaptations to climate, UV exposure, disease, diet, altitude, or cultural practice and have generated important genetic and phenotypic differences amongst populations.
In recent years, new methods to identify the genomic signatures of natural selection underlying these adaptations, combined with novel types of genetic data (e.g., ancient DNA), have provided unprecedented insights into the origin of adaptive alleles and the modes of adaptation. As a result, numerous instances of local adaptation have been identified in humans.
Here, we review the most exciting recent developments and discuss, in our view, the future of this field."
>But then why don’t we see any effect from excess winter heart attacks in very cold places like Stockholm or Siberia? Overall I’m not convinced of this one either.
Selection? This would be extremely interesting to study (genetically or epigenetically).
It's not the cold - it is the UV light that is missing in winter.
A whole host of physiological processes are dependent on UV light, vitamin D synthesis being the best known. But also nitrous oxide synthesis, lots of weird immunology and neurology are affected.
All the studies looking at excess winter deaths are the same as the ones looking at increased mortality from low vitamin D - they are measuring a surrogate for low UV exposure.
As a result, I expect global warming to be a net benefit as less clothing will being worn, hence elevated UV exposure.
Forgive me if this has been covered in the many, many comments below, but:
My understanding as to why flu is more prevalent in colder weather is that 1) sunlight kills germs, and there’s less sunlight (and people go outside less, which is perhaps the more important factor) in the winter, and 2) viruses don’t like humidity (for reasons I don’t quite understand). These at least seem to be the popular theories, and I would think that they at least deserve a mention, if only to dismiss them.
On a separate note, I’ve gone from “global warming will decrease cold deaths less than it will increase heat deaths” to “I’ve heard that that’s not true, and so now I don’t know,” to, now that I’ve read this article, “it looks like cold and heat deaths are mostly about human adaptation or lack thereof, so there’s no real way to tell what the effect will be—probably very little, but, as always, worse in poorer areas."
>The lowest recorded temperature in Kampala, Uganda was 12C (54F). Most years it doesn’t even get that low! Who’s dying from that?
Ok so it's clear you haven't been to Kampala in the winter, because 12C when it's usually >35 is absolutely freezing. The people in Kampala are certainly all wearing mittens and fur coats when it's 12C; I spent a couple of months in a similar place and if it reached 12C that was bad. Not only that, but 12C without heating at night is even worse. If you don't have super warm blankets and try to sleep in an unheated house as 12C you will certainly get sick. Add to that the fact that if it's 12C at night it might still be 35C in the day a few weeks later. The sudden temperature swings are what people say triggers the flu wave; not sure if true but certainly seemed plausible.
I know it's probably impossible to measure well, but whenever I see something like this, I always wish that we could get a measure of QALYs rather than deaths.
Because if it's like 'these terminally-ill bed-ridden 90+ year-olds are going to die from something in the next year or two, and it turned out to be becaus their hospice nurse was 20 minutes late because of snow on the road', then my reaction to that is very different from 'healthy people in the prime of their lives get freak heart attacks from constricted blood vessels when otherwise they would have lived another 50 healthy years'.
Extremely related, just came out:
https://direct.mit.edu/rest/article-abstract/103/4/740/97668/Adaptation-and-the-Mortality-Effects-of?redirectedFrom=fulltext
Very interesting. A suggested wider take at https://wordpress.com/post/phenell.wordpress.com/6516
> I find this suspicious, and I wonder if there are a bunch of less obvious seasonal viruses going around causing deaths that don’t get recorded as “seasonal viruses”. Or: we know that sometimes people can get strokes and heart attacks as complications of the flu - maybe we don’t notice the flu, or coroners don’t record it, and it just gets marked as a stroke or heart attack.
I had exactly this discussion with my partner who is a doctor. I had been speculating that our increasing understanding of COVID complications like strokes, clotting, heart attacks, etc. likely indicates that there are all sorts of complications with other common illnesses that we never studied deeply enough noticed before, and so we may have underestimated those numbers for years. Comparing like vs. like against COVID will be a shifting game for years if this is true.
Unfortunately this will also probably be used as justification by both sides of the lockdown debate.
I think you are on to something with extreme weather, as it is experienced locally, being the culprit. We had a bad heat wave in Oregon recently and a lot of older people died. It was even worse in British Columbia.
It wasn't the old people who needed to be cared for by other people who died. The victims tended to be independent old people who lived alone. My mother is really old, but she grew up in the tropics and rolled her eyes at me when I gave her advice about how to keep cool. She was fine even without air conditioning.
It was pretty hot, but I doubt if comparable heat in the Deep South would have had the same impact. A lot of the harm of extreme weather is going to fall on frail people who don't know how to cope. A young, fit person can deal with stress that will kill an old person. It will suck for them, but they'll live. Old people don't have the same margin of error, and if they don't have the experience to deal with the weather event they are far more likely to die.
There are a lot of simple things that people do every day that are taken for granted, but in aggregate they matter a lot. I think many lives could be saved by educating people who have narrow margins for survival how to survive rare events.
As for winter being a problem in tropical countries... I'm not sure about the flu being the culprit. What's the weather like during winter? Does it rain more? Does it flood? I'm with you on the temperature not being the cause but correlating with something else going on.
That excess winter death graph you have is interesting. The Netherlands, Belgium and France are right next to each other, but their data points are very far apart. Half of Belgium is Dutch, the other half is French, so IDK what the hell is going on.
Can somebody explain what the "minimum monthly temperature" means in the plot? Because I'm from Portugal and I'm sure it gets well below 10C there in the Winter...
One possibility is that people choose to rest during periods of "aberrant" temperature (heat in the tropical regions, cold in the cold regions). While you are resting (sleeping, siesta, whatever) at home, you are LESS likely to die.
So, the actual effect may be that cold death rates in sub Saharan Africa are "normal" and heats results in lower than "norm" death dur to lack of exertion. The opposite with heat in the cold regions.
Just another (possible) way to frame the data.
SB
Maybe influenza (and other seasonal viruses) are cyclical by nature (evolution/mutation load in ARN viruses together with group immunity can lead to that, in a typical cyclic predator/prey dynamic), so a rather weak and local periodic signal (winter in the more densely populated regions for example) will act as a sychronizing clock to the inherently non-linear cyclical epidemy. This signal can be weak, with period variation, even skip a beat from time to time, while the response stay strong with a more stable period than the trigger...
This is also a postulated mechanism for global climate periodic variation (glaciation, oceanic cyclic oscillations), and quite a convincing argument on how relatively stable periodic phenomenon occurs seemingly out of nowhere...
Surely it's all the indirect reasons that are most accountable. From what I understand, 'crop yield down -> guy somewhat poorer -> more stressed and heart attack' would also get captured by their function.
I tried discussing this on r/AskScienceDiscussion a few months ago: https://www.reddit.com/r/AskScienceDiscussion/comments/ns0qnr/recent_study_estimated_the_number_of_extra/. A few take aways:
- The estimations of the number of deaths due to Climate Change are dominated by deaths due to malaria and famines, both of which seem preventable by non-climate-related methods, i.e. better treatments for malaria (which are being worked on) and either some economic or humanitarian measures to mitigate the effects of localized droughts.
- Even if you consider the deaths from hypothermia alone (which are definitely cold-related -- it's there in the name), you'll end up with at the very least 50000 death per year, probably more, which is higher than the number of deaths from heat.
- That said, it is not clear how climate change will affect hypothermia, because deaths from it occur during unusual cold spells, and their frequency and severity may actually be increased due to climate change, because it increases the variance in weather events.
Isn’t the seasonality of the flu mostly due to solar radiation?
For example, the reference amount of sun (Philly, noon summer sun) kills covid-19 samples at an exponential rate of 90% every 6.8 minutes. https://academic.oup.com/jid/article/222/2/214/5841129
UV sources;
https://www.cpc.ncep.noaa.gov/products/stratosphere/uv_index/gif_files/diurnal.gif
https://www.cpc.ncep.noaa.gov/products/stratosphere/uv_index/
So there’s a clear hypothesis why warmer places have higher winter mortality; they get a similar variation in UV light, plus the warmth is good for bacterial and viral growth and survival.
One possible (partial) explanation for the unintuitive effects is that a lot of the investment/infrastructure that reduces weather-related mortality-- heating, air conditioning, social norms that reduce time spent outside in poor conditions-- aren't really about mortality. They're about enjoying life and being comfortable. So sure, warm places might invest more in AC and maybe won't invest in good insulation and back-up heating systems. And as a result, they'll be more susceptible to mortality to cold than heat. But they weren't trying to equate the marginal cost of mortality prevention across hot and cold days... they were trying to equate the marginal cost of *enjoying life*. Growing up in a cold climate, the first even remotely warm day of May, my parents would take my brother and I to the lake and we'd exhaust ourselves swimming in the frigid water. Later, in college, that same warm May day would be an occasion for excessive binge drinking on our outdoor couch. Beach-going and alcohol are probably bad for maximizing life expectancy, but certainly good for something.
Some related observations:
1. Deaths in tropical EU are practically not seasonal. Below is a chart I made for covid tracking reasons for Overseas Territories of France, the gray line is the average of weekly deaths in 2016-19.
2. Most of the studies I have seen uses daily average temperature. Maximum and minimum may be more relevant. For example, without air conditioning a lot of people have trouble to have a good night’s sleep when the minimum is more than 24C.
3. Climate/weather is more than temperature: for example, weather fronts are known to have large health effects, and weather fronts can be seasonal. Also, wet bulb temperature can be very different from actual temperature.
4. There can be a lagged effect of cold/hot weather, with some kind of accumulated damage/depleted resources (vitamin D, other vitamins etc.). The post mentions it, but it can be even longer lasting than just the extreme weather spell (there could be a decline throughout winter).
5. The ultimate question is whether apart from seasonality, overall mortality is lower in places with “better” climate (this may be difficult to define). There are many confounding factors, income, smoking etc., but within the EU at least, there is some evidence that the further South a location is, the higher is life expectancy (there is data for NUTS2 regions). The Madrid region has the highest life expectancy amongst EU regions. Corsica, Caribbean islands of France are pretty well placed too. In the detailed data though, as far as I remember, this results mainly from lower cardiovascular and cancer deaths – it would be a very important area to study.
6. There is a large difference between life expectancy of US regions and EU regions (latter is typically higher), if anyone has studies that compare seasonality, please link it here (i.e. is it mainly excess winter deaths, or is it higher all year around).
> Why would cold places adapt so hard that they did better than warm places? I don’t know, but this is what everybody says.
> I still don’t really get why cold cities over-adapt and end up with even lower mortality than the warm ones.
(I'm confused by the overall picture too.)
That's probably because many of these adaptations are discrete, not continuous. There's a certain cost in turning the heating slightly up or down (which is continuous), but the main cost is setting up the infrastructure. If you have 80% of the pipes needed for central heating to work, you don't have 80% of the heating, you just get a plumbing mess.
Are we dismissing the idea that temperatures that seem moderate to you are highly uncomfortable for people born in a different area? -- so I imagine the people are adapted to that temperature, and they function less well in other areas. There's long term and short term adjustment -- apparently stuff like the number of sweat glands you have is calibrated based on how hot it is for your mother when you're in the womb; other stuff is multi-generational adjustment.
But anyways, just anecdotally, I know people from much colder climates and much hotter climates who self report as being less comfortable and less healthy whatever they do. Even if you cover up, you're still having to breathe in a lot of cold air all the time if you're from a culture where covering your face is weird (or maybe with covid, that taboo has been busted?); but it's self-reported so who knows.
Separate question: how do we deal with the issue that death is inevitable when looking at these numbers? I've always wondered about the fact that presumably above a certain age, when death is inevitably just around the corner and you only need to make a mistake -- if causes of death are zero sum: reducing the number of deaths from falling down the stairs has to be balanced by deaths from some other source, because it's inevitable -- modulo extending someone's life by a year. I guess this is why people focus on deaths to youngish people?
If you are a stranger in Florida on an epic hot / humid day you are surrounded by people who are experts in surviving that climate with the necessary infrastructure to survive. If you show up on a very rare epic cold day you surrounded by idiots who don't have a clue what to do.
Law of Small Numbers? Greenland has population ~ 60,000. Extreme results are more prone to come from small samples.
> The lowest recorded temperature in Kampala, Uganda was 12C (54F). Most years it doesn’t even get that low! Who’s dying from that?
Try being in that temperature without proper clothes. I am pretty sure that it is enough.
I was sleeping in test 12 C with clothes for 16 C and it was miserable. I would not be surprised by frail person with clothes for 26 C dying.
And poor weather to that like rain or wind and lack of high quality tent and add illness/malnutrition on top of that. And I would be even less surprised.
Many years ago I remember (anecdote alert) that the radio news reported that missing persons were often found dead in the countryside, and to have died from 'exposure'.
It's quite possible that people who are warm in the day through activity, climate, or shelter nonethe less die of 'cold' or 'exposure' overnight because of the reduced activity and shelter even if the temperature is not absolutely cold in temperature terms. I imagine that people in Africa might find the nights lethally cool if there was no cloud cover or shelter.
FWIW
Hyperthermia death
https://www.washingtonpost.com/nation/2021/10/21/california-family-dead-hiking/
Birds carry the Flu viruses, so perhaps the cause are migrations, not the weather.
In extremely poor regions of South America and Africa, it happens that people die in winter during sleep because they use charcoal for heating and get suffocated.
If HxNy were the only flu strain, we would approach herd immunity within several years, even through a cold winter. So the flu continues to mutate into different strains to evade immunity, and one of the major unmentioned factors here is this strain churn, means a (in reality, a set of dozens of) different strains circulates through populations each year. The consistent cyclicality of flu season is largely driven by strain churn, but that still doesn't explain the peak/trough and their correlation to seasons.
I'd speculate summer as the selection bottleneck in highly seasonal regions, and winter as the exponential part of infection S-curve of a novel infectious agent. So: it's summer is northern Eurasia, and the living is easy, except for the immuno-compromised. Which strain is best able to make it through the summer? This is largely driven by which strain does the immune system have the least memory of. And since the immuno-compromised are usually old, this is perfect for finding something most other people have never been exposed to either.
Now it's September, and the flu has faced a 99% mass extinction event - especially around the previous year's strain where R0 is approaching less than one. Whichever funky new (so old, it's new) strain was able to hang on and continue to infect is going to well poised to spread through the rest of the population. Through travel, hajj's, agrarian laborers etc, these selected for strains again move throughout the world causing another peak. Immunity to the new strain builds, and then we do the summer selection process all over again.
"We still don’t really understand why the flu is seasonal."
Is anyone looking into migratory bird patterns? I'm surprised that the Wiki article didn't even mention those as relevant.
Waterfowl like ducks are reservoirs for influenza strains and migratory birds are known to be important to influenza's evolution and spread.
"Virologic surveillance of apparently healthy birds has established that the waterfowl of the world are the natural reservoirs of all known influenza A viruses. The Anseriformes (waterfowl) and Charadriiformes (shorebirds and gulls) are the major reservoirs in which the 16 HA and nine NA subtypes are perpetuated"
https://journals.plos.org/plospathogens/article?id=10.1371/journal.ppat.0030167
A common chain of transmission is that a virus will spread from migratory birds to farm-birds like ducks to farm birds like chickens sometimes passing through pigs and finally to humans.
It seems notable that the % overall excess death ratio reported in the Zhao et al. study throws up the most extreme and counterintuitive results in areas where the study's data is very poor and the temperatures are very extreme. It looks like they only had daily time-series data on mortality for 43 countries and extrapolated their mortality rates for all other areas based on factors like GDP/capita and daily temperature ranges. Some areas in sub-Saharan Africa and central Asia have extrapolated excess death rates (for counterintuitive causes of death) as high as 20-25%, which is WILD, and these areas seem to correspond with a) a lack of daily time-series mortality data for that location b) low GDP/capita and c) extreme local temperatures. It's possible that these simply ARE the conditions under which extreme counterintuitive mortality rate increases occur, but it feels much more like a model being left to its own devices and getting a little wibbly around the edges when the data is spotty.
(It's also worth noting that the scales on the map of annual average heat related deaths in Fig. 3 look suspiciously data-crime-y, but that's more of a procedural quibble than a criticism of the article. I bring it up here because without paying attention to the scales of the graphs it looks deceptively like the rate of heat related deaths for Europe [where there data is good] is very high.)
I find myself mulling over whether there is any correlation between the average wealth of a culture, and the rate of deaths related to either extreme cold or extreme heat. But I also am trying to figure out how pre-industrial cultures and civilizations dealt with extreme weather.
Do we have good data for deaths due to extreme weather among the Dorset people, or Icelandic settlers, in Greenland 1000 years ago? Between the two groups of people, I would suspect that the Icelandic culture was slightly wealthier. Did this affect survival rates during the transition from Medieval Warm Period to Little Ice Age?
What about the Thule people, who replaced both groups in Greenland? Were they wealthier, or not?
If any of these three groups had a better ability to survive in climatic extremes, it was more a product of culturally-learned behavior than of genetics or economic success.
I suspect that this pattern shows up in many of the examples cited for deaths due to hypothermia during a cold snap in warm climates, or deaths due to heat stroke in a cold climate. If the problem hasn't shown up often enough to generate a cultural story of what not to do in that scenario, then the likelihood of a person choosing to do something foolish increases.
The wealth of a culture can put a layer of protection around a person. It can reduce the need for the transmission of cultural knowledge. In some cultures, it was the knowledge about how to keep warm sleeping on the ground. In other cultures, it was the knowledge about how to keep cool when the temperature stays hot all day and night for many weeks on end.
Sorry, I didn't read all the comments, and certainly someone else mentioned this - so apologies to them, but I think you're looking at this the wrong way. You finally touch on this at the end of the article, but you use the word "because" as it relates to death which I believe has distorted your thinking. People don't die "because" of the flu, the heat, the cold, etc. People die. (hard period). However people die * sooner than we might like * "because" of the heat, cold, etc. So, the only stat that makes sense and what you need to look at is Years of Life Lost (YLL), or better yet Years of Quality Life Lost. Deaths will go up short term during the cold and heat, but a careful analysis should (perhaps) look at the annual death rates and see if during a year with higher than average temperature in a region the annual death rate has increased. I'm not saying it's not a tragedy when a certain percentage of the population dies 6 months sooner than they normally might, but that doesn't have the same implication as "10% of all deaths are due to cold".
One problem with "hot cities have worse life expectancy" is that hot cities also have lower income and otherwise differ demographically.
If you look at North America and Europe, the most affluent countries are in the north, and the poorest are in the south. Moreover, further north in the US, there are generally fewer black people on average, and more Asians, and blacks have higher mortality rates than whites do while Asians have lower mortality rates and live longer.
Hawaii - a tropical state with very few black people, but enormous numbers of Asians - has the highest life expectancy of any state. California, which has a lot of Asians and Hispanics (both of which have above-white life expectancy in the US) has the second highest life expectancy, despite being a hotter state. Indeed, the US north/south cline is mostly because of the South, which is also extremely obese, which is likely another significant driver of the trend.
As such, this really seems likely to be a "richer places live longer" thing... which makes the trendline completely worthless. The rich places that are pretty hot - like Hong Kong and Singapore - have quite long life expectancy, and Australia, which is also a pretty hot country, also has a good life expectancy. These "abnormalities" are simply the result of there not being many developed regions in hotter areas of the world.
And with regards to mortality rate increasing over the 21st century, this is goin to happen regardless of global warming, because the population is getting older on average because people are having fewer kids. So it's kind of worthless to project that mortality rates are going to rise, because no matter what we do, they're going to go up simply because there will be a higher percentage of old people in the population, especially in developed countries.
Okay, simple correlation: more exposure to sunshine = higher serum Vitamin D3 levels. Countries that consume a lot of fish/fish oils will have consistently higher levels of Vitamin D3 during periods when the population has lower exposure to sunlight. Higher levels of Vitamin D3 provide higher levels of protection against diseases and blood clotting/strokes/heart attacks.
Lancet article says: https://www.thelancet.com/journals/lanplh/article/PIIS2542-5196(21)00081-4/fulltext tl;dr: "Globally, 5 083 173 deaths were associated with non-optimal temperatures per year, 9·43% of all deaths were cold-related and 0·91% were heat-related). ... Eastern Europe had the highest heat-related excess death rate and Sub-Saharan Africa had the highest cold-related excess death rate. ... From 2000–03 to 2016–19, the global cold-related excess death ratio changed by −0·51 percentage points and the global heat-related excess death ratio increased by 0·21 percentage points, leading to a net reduction in the overall ratio." - Cheers, global warming for saving millions from premature death this century! Ahrrg, "millions" - so it's just statistics ... :(
theory that flu cases rise in the winter due to people spending more https://www.scholarshipbundle.com/2022/02/list-of-fully-funded-phd-programs-2022.html
Influenza virus prefers cold temperatures and low humidity. https://www.scholarshipbundle.com/2022/04/queen-elizabeth-commonwealth.html
Influenza virus prefers cold temperatures and low humidity. https://www.scholarshipbundle.com/2022/04/sydney-scholars-awards-in-australia.html
https://www.scholarshipbundle.com/2022/03/clean-government-scholarship-2022-23.html
https://www.scholarshipbundle.com/2022/03/eui-young-african-leaders-program-2022.html
https://healthy-structure.blogspot.com/2023/03/how-to-get-rid-of-keloids-keloid-scar.html