Great explanation of heat-related mortality numbers. I've wondered how those numbers are derived, since there are so many variables and temperatures are often not that extreme. It's not like the opening scene in the book "Ministry for the Future".
It strikes me it would help this discussion dramatically if someone mentioned that we need to not the question 'how many people are killed by heat?', but rather 'how many people are killed by heat plus poverty?'
If the recorded temperature for a day is 24 degrees (Celcius), the heat in a non air-conditioned flat in the attic with windows that won't open could be much, much more. And the ambient temperature in a high-density heat island covered with asphalt roads and roofs is going to be a lot hotter than in a suburb with mature trees lining the streets.
Assuming-out the problem of wealth-stratification really makes the discussion somewhat meaningless.
In the case of the European heat waves, a lot of the deaths were because the houses were built to retain heat. It wasn't just that they didn't have air conditioning, but that there was little ventilation and the apartments/townhouses could be hotter than outside.
My childhood home in New Orleans was built without A/C with high ceilings, big windows and a breezy screen porch. In Massachusetts, the old boxy Victorian era home I lived in was stifling in the summer, even at lower temps than we had in NOLA.
I agree that more, longer and hotter heat waves will disproportionately affect poor people. All global warming's costs fall more heavily on those with fewer resources to adapt. 'Twas ever thus (https://en.wikipedia.org/wiki/Matthew_effect)!
The poor will always be with you (St. Matthew again). Discussing total heat deaths, OTOH, is meaningful because a rising trend is easily understood by anyone not in denial, as a clear consequence of continued fossil carbon emissions: heat-related deaths will rise as long as atmospheric CO2 does, and the more people who know that, the more likely they'll act collectively to cap the mortality trend by decarbonizing their national economies. AFAICT, that's the underlying meaning of Dr. Dessler's post.
In the USA, for example, it will take less than 2% more Democratic votes than in 2024, to overturn all our preposterous POTUS's actions on behalf of fossil fuel producers and investors, and put us back on the decarbonization path begun by the previous Democratic administration and Congress. Meanwhile, the percentage of Americans who are "alarmed" or "concerned" about climate change has risen yearly (https://climatecommunication.yale.edu/about/projects/global-warmings-six-americas/), although Trump's sanctioning of denialism has enabled a slight reversal since 2024. Official denialism notwithstanding, every broken extreme-weather record we hear about raises the level of voters' concern. My fellow Americans, please vote Democratic, as the defacto party of collective action for public good in our country: at least until some Republican candidate publicly repudiates their party's decades-old anti-decarbonization plank.
Actually, I was trying to point out that heat death numbers will be substantively different in a nation with less wealth-stratification because there will be fewer non air-conditioned apartments with windows that don’t open in heat islands with too many people living there.
Trying to come up with numbers that show the result of climate change without any attempt to control for different rates of adaptation by the populace are bound to be suspect.
I didn’t make the most clear comment, but I wasn’t just trying to inject a moral or emotional concern (although those do exist), but rather quibbling about the statistical science.
The problem with improvement projects in poor neighborhoods is that making the neighborhood ·nicer· means more people want to live there and the rents go up. It's how gentrification starts.
Another differentiator is who can still *run* air conditioners after the power goes out. (Local organizations in New Orleans got together to form community cooling centers and they've since been integrated into the municipal government.)
Thanks, and I wasn't actually criticizing you. Your first and last sentences in your initial comment seemed pretty clear, though: you're pointing out the fundamental economic injustice of anthropogenic climate change as the principle moral concern in this discussion. FWIW, I agree.
TBH, your comment was mainly an opportunity to identify ongoing climate change as a manifestation of the class warfare that has driven history since the spread of agriculture, and the rationale for collectively decarbonizing the US and global economies despite the morally repugnant, sadly successful disinformation campaign by carbon capitalists to protect their profit streams.
Thanks for clarifying this. However, you refer only to numbers and not the fraction of the population. Since the population itself is presumably increasing, more people would be dying, regardless? This thought also raises questions about changes in the population itself in terms of ethnic factors, diet, air conditioning, and so forth. If there is a major flood and people die, it it split off, or attributed to "heat". Carry on. Thanks, Kevin
Great article Andrew. The 2 factors that scare me beyond the actual temp are the humidity and the increase chance of power failure when everyone cranks up their a/c's on sweltering days. We are in a new unchartered territory now.
In the past, Texas' grid (run by ERCOT) used to resort to rolling blackouts during record demand. These past few years have seen much higher demand (higher temps x higher population), yet between the solar and battery additions not only do we have enough supply but it's *cheaper* than when they had to rely on gas peaker plants.
No matter how much power is on the grid, though, that doesn't address local power outages that come with storms.
Allegedly cheapest source of power (solar) produces at its peak during the heatwaves (most sunny days, although heat reduces output). Shouldn't be a problem (sarcasm). Few years ago it used to be popular to say that conventional grids are not needed, outdated and expensive instruments. Just now more and more clean, reliable and cheap power is needed.
Indeed, my biggest fear during the lethal PNW heatwave of 2021 was that my utility power would fail, and my heat pump with it. Thankfully, my power is over 50% hydro and renewable. When the heat pump eventually did fail a year ago, I replaced it for $7000 without hesitation, mindful of approaching summer. My next major home improvement will be solar panels and a battery.
saved this article! Thank you for talking about this. It’s important to make climate storytelling personal and understand the health impacts of a heatwave. I had no idea about the statistics
So if i understand correctly, there is no way of getting empirical evidence? Could we not compare over time and normalise for demographics rather then the option 3 which keeps the demographics constant and simulates the temperature? Or is that just verifying the smile curve.
And as im typing im now wondering if the smile curve is robust and we know extreme heat is increasing as per ipcc, then is that not enough evidence of an upwards trend?
An aspect that maybe is slightly outside of scope but could still be interesting to address, is the difference between US and Europe. I am not going to post them, but I remember reading what looked like trustable comparisons between heat death in Europe and the US, whereas there are many many more in Europe, due to indeed maladapted housing stock, and, unavoidably, much lower use of A/C.
This becomes a political argument because, in fact, American jingoists participating to this debate pointed out that this, a recurring difference in death, was much higher than the intercontinental difference running the other way for "gun" deaths, a much more politically charged subject.
This did kind of shock me a little bit. As I understand it, in most EU care homes A/C is compulsory and/or widespread, but that does not seem enough. Any thoughts?
That "u-shaped" curve of T v. mortality does not look like the curves I have seen in two different studies (URLs below): It's too symmetric around the optimal temperature. In those papers the rise in morbidity/mortality is much steeper on the heat side.
Further, those curves reflect the large difference in the physiological response of humans to cold vs. heat.
To retain heat in the cold we have vasoconstriction (to the extreme of frostbite), curling up to reduce surface area, huddling with other endotherms (e.g., "three dog night"), shivering, adding insulation (blankets) and increasing physical activity.
To shed heat we have evaporative cooling (sweat) and direct heat transfer (cooler surfaces or substances).
1) The OTM measurement comes across as something of a neoclassical economic fantasy, that there is somehow one (narrow) optimum temperature and deaths above that may relate in some way to climate change. In reality, humans are a physiologically adaptable mammal, able to adapt and thrive across a range of temperatures (hence our movement out of Africa). It seems to me that there must be a range of optimum temperatures across age and privilege (aging countries like Germany and Japan would show a greater mortality offset by relative wealth, for example).
2) Using 1950-1963 as a range may be inaccurate - effects of climate change started before that and using 1950-63 as a benchmark would already include a minority (at least) of deaths caused by climatically-affected temperatures.
3) Since 1950 the ability of autopsy/post-mortem analysis to determine causes and means of death has increased immeasurably (https://pmc.ncbi.nlm.nih.gov/articles/PMC12034628/), even though there are now substantial problems with autopsy reporting re cause of death. To compare causes of death from 1950-63 to today is to contrast bodies of evidence selected by entirely different toolsets and expertise.
Every lost life is sad, but the only certainties are death, taxes and renewable subsidies to unworthy greedy rent-seekers who have wrecked economies and wasted money that could be used for genuine environmental and health issues. Weak economies are the No.1 cause of premature deaths and renewables are a major cause of weakening economies. Look at Europe (especially Spain), UK & Australia that are de-industrializing and have refused to drill their own extensive petroleum resources and are now beggar nations.
More deaths are caused by infections in the bunions of elderly people, especially those with diabetes, than from the small percentage increase in summer heatwaves. I've seen this happen and it is deeply disturbing as the foot is eventually amputated. Where is the marching in the streets protesting against bunions? What are the policies of James Hansen, Al Gore and Greta Thunberg about the unfortunate truth of bunions? Where are the subsidies to tackle the bunion pandemic?
These summer heatwaves are bad. I can't install electricity-guzzling, CO2 emitting air-conditioning in my place and I can't install rooftop solar either. So, I cop it bad for a few days each year but I'm acclimatized to it.
Heatwaves can be especially awful in urbanized areas, but heatwaves today are still less severe than the heatwaves in the 1930s. In the 1970s, we watched New Yorkers turning-on the fire hydrants to cool-off when nobody had air-conditioning. And we had a great song by the Lov'in Spoonful band:
Anything that changes people’s underlying health will impact the death rate. So if the population ages or people are otherwise less healthy, the death rate will go up.
The Minoan, Greek and Roman civilizations prospered during equally intense warm periods with only primitive air conditioning. There seems to be an anthropomorphic technology inherited from our African savannah origins to handle heat. It's called shade, ventillation and hydration. Cold was a tougher challenge but fire, warm shelters and the needle for stitching animal-skin garments helped a lot. Humans succeeded because we are incredibly capable of adaptations to cope with climate variations and humans are still prospering in today's warming period.
With a positive economic approach, global civilization may be achieved late in this century. If we burden the 3rd world with inefficient, unreliable technologies, that will slow the spread of civilization egregiously.
Our rising excess death rates have deeper medico-socio-economic roots that health groups are researching worldwide. That topic is intensely debated and highly contentious.
A robust economy and an optimistic outlook are the most effective cures for the falling longevity rates in some western countries. Scaring the younger generation is dangerous because despair increases death rates far more than heat or cold could ever do. So scientists need to act responsibly.
"Humans succeeded because we are incredibly capable of adaptations to cope with climate variations and humans are still prospering in today's warming period."
Yes, some humans prospered during previous climate variations. Others died. Now more people are dying of heat-related causes than previously, and those numbers are increasing. Are you OK with that? Because the victims and their families presumably aren't.
"With a positive economic approach, global civilization may be achieved late in this century. If we burden the 3rd world with inefficient, unreliable technologies, that will slow the spread of civilization egregiously."
I cowered in my heat-pump-cooled manufactured home for three days in June 2021, hoping my power stayed on (it's >50% hydro and renewable, and didn't fail), while over 800 deaths in two states and two provinces were later attributed (https://www.nature.com/articles/s41467-023-36289-3) to gobsmackingly high daily maximum temperatures, absurdly improbable even without the 1.3°C of global warming since the Industrial Revolution accelerated the spread of "civilization" along with population growth. In a counterfactual world where burning fossil carbon does not cause global warming, those people almost certainly would not have died. Would they be glad knowing that in the factual world, civilization is still spreading?
Believe it or not, profit-driven CO2 emissions are already taking an egregious economic and human toll, and both are open-ended until fossil carbon is no longer being transferred to the atmosphere by the gigatonnes annually. And it's no longer necessary to socialize the private marginal cost of fossil carbon, to drive the spread of putative civilization. We need not burden the world with less reliable energy production technology, to decarbonize the global marketplace. The only thing obstructing decarbonization, is the money to be made by selling fossil carbon for all the traffic will bear while socializing the marginal climate-change cost out of the market price.
"Heat-related deaths" is a complicated subject. An aspect not covered in this short piece is the cumulative impact of previous heat exposures. So, death is not neatly attributable to one exposure. Previous high heat exposures can cause damage under the death threshold, then th enext exposure need not be so high to precipitate death. One can attempt to simplify death counts but it is the determination of causation is challenging because it is complicated.
The risk curves we used are derived from a lagged model that estimates mortality on a particular day from the temperature of the previous 21 days. So this impact is included, to some extent at least.
"To some degree" is a punny and trite dismissal of the point in that the damage can be cumulative over long periods (years). Also, how accurate is the attribution of coroners of cause of death? Kidney failure of someone on dialysis in the current political clime would likely be assessed as kidney failure due to long-term kidney health issues. While partially true, the deceased could possibly have lived years longer if not subjected to heat stress. So, the "error bars" in your piece's data are critical.
You're correct that deaths occurring more than a few weeks after exposure to a hot day won't be counted by this regression method. Attribution by coroners is not particularly good for heat, which is why their numbers should be considered a lower limit.
This is a great writeup. Has anyone examined whether the Optimal Temperature has changed over time? I'd think it might have increased with greater availability of air conditioning as the 20th Century progressed. But it might also have decreased (at least in some areas) as governments became more adept at dealing with snow and ice.
Could you apply the same methodology to deaths from cold? It would be interesting to compare increased deaths from heat to (presumably) decreased deaths from cold.
I never seen an analysis of how the OT has changed over time. You would need to get a very long-term data set of mortality, which might be hard to get. However, you can look at how OT changes between cities with different climates. What you find is that, as the climate warms, the OT increases. I'm guessing that would also happen over time as people adapt to warmer temperatures.
In theory, you can do the same calculation for the cold side of the risk curve. However, the parameterization we used for estimating the risk curves (from Shindell et al.) only parameterizes the hot side of the risk curve. So, you would need to parameterize the cold side as well. We did think about doing that but never got around to it.
“For that, we use what we refer to as the Excess Death Method (EDM). Our approach is to take today’s mortality risk curve (based on today’s population, today’s demographics, **today’s level of adaptation to heat**), but plug in the temperatures from a past period — in our analysis, we used 1950-1963.”
This seems worth highlighting considering that there is a fairly direct relationship between today’s warming and adaptation via the wealth.
If you’re interested in heat vs cold, I’ve previously written about this.
https://www.theclimatebrink.com/p/unraveling-the-debate-does-heat-or?r=27daj&triedRedirect=true
Great explanation of heat-related mortality numbers. I've wondered how those numbers are derived, since there are so many variables and temperatures are often not that extreme. It's not like the opening scene in the book "Ministry for the Future".
Thanks Andrew!
It strikes me it would help this discussion dramatically if someone mentioned that we need to not the question 'how many people are killed by heat?', but rather 'how many people are killed by heat plus poverty?'
If the recorded temperature for a day is 24 degrees (Celcius), the heat in a non air-conditioned flat in the attic with windows that won't open could be much, much more. And the ambient temperature in a high-density heat island covered with asphalt roads and roofs is going to be a lot hotter than in a suburb with mature trees lining the streets.
Assuming-out the problem of wealth-stratification really makes the discussion somewhat meaningless.
In the case of the European heat waves, a lot of the deaths were because the houses were built to retain heat. It wasn't just that they didn't have air conditioning, but that there was little ventilation and the apartments/townhouses could be hotter than outside.
My childhood home in New Orleans was built without A/C with high ceilings, big windows and a breezy screen porch. In Massachusetts, the old boxy Victorian era home I lived in was stifling in the summer, even at lower temps than we had in NOLA.
I agree that more, longer and hotter heat waves will disproportionately affect poor people. All global warming's costs fall more heavily on those with fewer resources to adapt. 'Twas ever thus (https://en.wikipedia.org/wiki/Matthew_effect)!
The poor will always be with you (St. Matthew again). Discussing total heat deaths, OTOH, is meaningful because a rising trend is easily understood by anyone not in denial, as a clear consequence of continued fossil carbon emissions: heat-related deaths will rise as long as atmospheric CO2 does, and the more people who know that, the more likely they'll act collectively to cap the mortality trend by decarbonizing their national economies. AFAICT, that's the underlying meaning of Dr. Dessler's post.
In the USA, for example, it will take less than 2% more Democratic votes than in 2024, to overturn all our preposterous POTUS's actions on behalf of fossil fuel producers and investors, and put us back on the decarbonization path begun by the previous Democratic administration and Congress. Meanwhile, the percentage of Americans who are "alarmed" or "concerned" about climate change has risen yearly (https://climatecommunication.yale.edu/about/projects/global-warmings-six-americas/), although Trump's sanctioning of denialism has enabled a slight reversal since 2024. Official denialism notwithstanding, every broken extreme-weather record we hear about raises the level of voters' concern. My fellow Americans, please vote Democratic, as the defacto party of collective action for public good in our country: at least until some Republican candidate publicly repudiates their party's decades-old anti-decarbonization plank.
Actually, I was trying to point out that heat death numbers will be substantively different in a nation with less wealth-stratification because there will be fewer non air-conditioned apartments with windows that don’t open in heat islands with too many people living there.
Trying to come up with numbers that show the result of climate change without any attempt to control for different rates of adaptation by the populace are bound to be suspect.
I didn’t make the most clear comment, but I wasn’t just trying to inject a moral or emotional concern (although those do exist), but rather quibbling about the statistical science.
The problem with improvement projects in poor neighborhoods is that making the neighborhood ·nicer· means more people want to live there and the rents go up. It's how gentrification starts.
Another differentiator is who can still *run* air conditioners after the power goes out. (Local organizations in New Orleans got together to form community cooling centers and they've since been integrated into the municipal government.)
Thanks, and I wasn't actually criticizing you. Your first and last sentences in your initial comment seemed pretty clear, though: you're pointing out the fundamental economic injustice of anthropogenic climate change as the principle moral concern in this discussion. FWIW, I agree.
TBH, your comment was mainly an opportunity to identify ongoing climate change as a manifestation of the class warfare that has driven history since the spread of agriculture, and the rationale for collectively decarbonizing the US and global economies despite the morally repugnant, sadly successful disinformation campaign by carbon capitalists to protect their profit streams.
Thanks for clarifying this. However, you refer only to numbers and not the fraction of the population. Since the population itself is presumably increasing, more people would be dying, regardless? This thought also raises questions about changes in the population itself in terms of ethnic factors, diet, air conditioning, and so forth. If there is a major flood and people die, it it split off, or attributed to "heat". Carry on. Thanks, Kevin
Great article Andrew. The 2 factors that scare me beyond the actual temp are the humidity and the increase chance of power failure when everyone cranks up their a/c's on sweltering days. We are in a new unchartered territory now.
In the past, Texas' grid (run by ERCOT) used to resort to rolling blackouts during record demand. These past few years have seen much higher demand (higher temps x higher population), yet between the solar and battery additions not only do we have enough supply but it's *cheaper* than when they had to rely on gas peaker plants.
No matter how much power is on the grid, though, that doesn't address local power outages that come with storms.
Allegedly cheapest source of power (solar) produces at its peak during the heatwaves (most sunny days, although heat reduces output). Shouldn't be a problem (sarcasm). Few years ago it used to be popular to say that conventional grids are not needed, outdated and expensive instruments. Just now more and more clean, reliable and cheap power is needed.
That is yet another super good argument for distributed solar. A heatwave can kill many who rely on a failed grid.
Indeed, my biggest fear during the lethal PNW heatwave of 2021 was that my utility power would fail, and my heat pump with it. Thankfully, my power is over 50% hydro and renewable. When the heat pump eventually did fail a year ago, I replaced it for $7000 without hesitation, mindful of approaching summer. My next major home improvement will be solar panels and a battery.
saved this article! Thank you for talking about this. It’s important to make climate storytelling personal and understand the health impacts of a heatwave. I had no idea about the statistics
On my climate blog, I just wrote an article about what my country, India, is going through officially being the hottest country on earth right now and it’s important for every country to realize why this is happening. Do give it a read! https://substack.com/@susitout/note/p-199003713?r=3pcwen&utm_medium=ios&utm_source=notes-share-action
So if i understand correctly, there is no way of getting empirical evidence? Could we not compare over time and normalise for demographics rather then the option 3 which keeps the demographics constant and simulates the temperature? Or is that just verifying the smile curve.
And as im typing im now wondering if the smile curve is robust and we know extreme heat is increasing as per ipcc, then is that not enough evidence of an upwards trend?
An aspect that maybe is slightly outside of scope but could still be interesting to address, is the difference between US and Europe. I am not going to post them, but I remember reading what looked like trustable comparisons between heat death in Europe and the US, whereas there are many many more in Europe, due to indeed maladapted housing stock, and, unavoidably, much lower use of A/C.
This becomes a political argument because, in fact, American jingoists participating to this debate pointed out that this, a recurring difference in death, was much higher than the intercontinental difference running the other way for "gun" deaths, a much more politically charged subject.
This did kind of shock me a little bit. As I understand it, in most EU care homes A/C is compulsory and/or widespread, but that does not seem enough. Any thoughts?
That "u-shaped" curve of T v. mortality does not look like the curves I have seen in two different studies (URLs below): It's too symmetric around the optimal temperature. In those papers the rise in morbidity/mortality is much steeper on the heat side.
Further, those curves reflect the large difference in the physiological response of humans to cold vs. heat.
To retain heat in the cold we have vasoconstriction (to the extreme of frostbite), curling up to reduce surface area, huddling with other endotherms (e.g., "three dog night"), shivering, adding insulation (blankets) and increasing physical activity.
To shed heat we have evaporative cooling (sweat) and direct heat transfer (cooler surfaces or substances).
https://www.nature.com/articles/s41467-020-16273-x
https://www.thelancet.com/journals/lanplh/article/piis2542-5196%2823%2900023-2/fulltext
1) The OTM measurement comes across as something of a neoclassical economic fantasy, that there is somehow one (narrow) optimum temperature and deaths above that may relate in some way to climate change. In reality, humans are a physiologically adaptable mammal, able to adapt and thrive across a range of temperatures (hence our movement out of Africa). It seems to me that there must be a range of optimum temperatures across age and privilege (aging countries like Germany and Japan would show a greater mortality offset by relative wealth, for example).
2) Using 1950-1963 as a range may be inaccurate - effects of climate change started before that and using 1950-63 as a benchmark would already include a minority (at least) of deaths caused by climatically-affected temperatures.
3) Since 1950 the ability of autopsy/post-mortem analysis to determine causes and means of death has increased immeasurably (https://pmc.ncbi.nlm.nih.gov/articles/PMC12034628/), even though there are now substantial problems with autopsy reporting re cause of death. To compare causes of death from 1950-63 to today is to contrast bodies of evidence selected by entirely different toolsets and expertise.
Every lost life is sad, but the only certainties are death, taxes and renewable subsidies to unworthy greedy rent-seekers who have wrecked economies and wasted money that could be used for genuine environmental and health issues. Weak economies are the No.1 cause of premature deaths and renewables are a major cause of weakening economies. Look at Europe (especially Spain), UK & Australia that are de-industrializing and have refused to drill their own extensive petroleum resources and are now beggar nations.
More deaths are caused by infections in the bunions of elderly people, especially those with diabetes, than from the small percentage increase in summer heatwaves. I've seen this happen and it is deeply disturbing as the foot is eventually amputated. Where is the marching in the streets protesting against bunions? What are the policies of James Hansen, Al Gore and Greta Thunberg about the unfortunate truth of bunions? Where are the subsidies to tackle the bunion pandemic?
These summer heatwaves are bad. I can't install electricity-guzzling, CO2 emitting air-conditioning in my place and I can't install rooftop solar either. So, I cop it bad for a few days each year but I'm acclimatized to it.
Heatwaves can be especially awful in urbanized areas, but heatwaves today are still less severe than the heatwaves in the 1930s. In the 1970s, we watched New Yorkers turning-on the fire hydrants to cool-off when nobody had air-conditioning. And we had a great song by the Lov'in Spoonful band:
Hot town, summer in the city
Back of my neck gettin' dirty and gritty
Been down, isn't it a pity?
Doesn't seem to be a shadow in the city
Does the increase in obesity have an impact?
Anything that changes people’s underlying health will impact the death rate. So if the population ages or people are otherwise less healthy, the death rate will go up.
Obesity can save in extreme cold. Not a great reason to get fat
The Minoan, Greek and Roman civilizations prospered during equally intense warm periods with only primitive air conditioning. There seems to be an anthropomorphic technology inherited from our African savannah origins to handle heat. It's called shade, ventillation and hydration. Cold was a tougher challenge but fire, warm shelters and the needle for stitching animal-skin garments helped a lot. Humans succeeded because we are incredibly capable of adaptations to cope with climate variations and humans are still prospering in today's warming period.
With a positive economic approach, global civilization may be achieved late in this century. If we burden the 3rd world with inefficient, unreliable technologies, that will slow the spread of civilization egregiously.
Our rising excess death rates have deeper medico-socio-economic roots that health groups are researching worldwide. That topic is intensely debated and highly contentious.
A robust economy and an optimistic outlook are the most effective cures for the falling longevity rates in some western countries. Scaring the younger generation is dangerous because despair increases death rates far more than heat or cold could ever do. So scientists need to act responsibly.
"Humans succeeded because we are incredibly capable of adaptations to cope with climate variations and humans are still prospering in today's warming period."
Yes, some humans prospered during previous climate variations. Others died. Now more people are dying of heat-related causes than previously, and those numbers are increasing. Are you OK with that? Because the victims and their families presumably aren't.
"With a positive economic approach, global civilization may be achieved late in this century. If we burden the 3rd world with inefficient, unreliable technologies, that will slow the spread of civilization egregiously."
I cowered in my heat-pump-cooled manufactured home for three days in June 2021, hoping my power stayed on (it's >50% hydro and renewable, and didn't fail), while over 800 deaths in two states and two provinces were later attributed (https://www.nature.com/articles/s41467-023-36289-3) to gobsmackingly high daily maximum temperatures, absurdly improbable even without the 1.3°C of global warming since the Industrial Revolution accelerated the spread of "civilization" along with population growth. In a counterfactual world where burning fossil carbon does not cause global warming, those people almost certainly would not have died. Would they be glad knowing that in the factual world, civilization is still spreading?
Believe it or not, profit-driven CO2 emissions are already taking an egregious economic and human toll, and both are open-ended until fossil carbon is no longer being transferred to the atmosphere by the gigatonnes annually. And it's no longer necessary to socialize the private marginal cost of fossil carbon, to drive the spread of putative civilization. We need not burden the world with less reliable energy production technology, to decarbonize the global marketplace. The only thing obstructing decarbonization, is the money to be made by selling fossil carbon for all the traffic will bear while socializing the marginal climate-change cost out of the market price.
"Heat-related deaths" is a complicated subject. An aspect not covered in this short piece is the cumulative impact of previous heat exposures. So, death is not neatly attributable to one exposure. Previous high heat exposures can cause damage under the death threshold, then th enext exposure need not be so high to precipitate death. One can attempt to simplify death counts but it is the determination of causation is challenging because it is complicated.
The risk curves we used are derived from a lagged model that estimates mortality on a particular day from the temperature of the previous 21 days. So this impact is included, to some extent at least.
"To some degree" is a punny and trite dismissal of the point in that the damage can be cumulative over long periods (years). Also, how accurate is the attribution of coroners of cause of death? Kidney failure of someone on dialysis in the current political clime would likely be assessed as kidney failure due to long-term kidney health issues. While partially true, the deceased could possibly have lived years longer if not subjected to heat stress. So, the "error bars" in your piece's data are critical.
You're correct that deaths occurring more than a few weeks after exposure to a hot day won't be counted by this regression method. Attribution by coroners is not particularly good for heat, which is why their numbers should be considered a lower limit.
This is a great writeup. Has anyone examined whether the Optimal Temperature has changed over time? I'd think it might have increased with greater availability of air conditioning as the 20th Century progressed. But it might also have decreased (at least in some areas) as governments became more adept at dealing with snow and ice.
Could you apply the same methodology to deaths from cold? It would be interesting to compare increased deaths from heat to (presumably) decreased deaths from cold.
I never seen an analysis of how the OT has changed over time. You would need to get a very long-term data set of mortality, which might be hard to get. However, you can look at how OT changes between cities with different climates. What you find is that, as the climate warms, the OT increases. I'm guessing that would also happen over time as people adapt to warmer temperatures.
In theory, you can do the same calculation for the cold side of the risk curve. However, the parameterization we used for estimating the risk curves (from Shindell et al.) only parameterizes the hot side of the risk curve. So, you would need to parameterize the cold side as well. We did think about doing that but never got around to it.
“For that, we use what we refer to as the Excess Death Method (EDM). Our approach is to take today’s mortality risk curve (based on today’s population, today’s demographics, **today’s level of adaptation to heat**), but plug in the temperatures from a past period — in our analysis, we used 1950-1963.”
This seems worth highlighting considering that there is a fairly direct relationship between today’s warming and adaptation via the wealth.