The burden of heat-related mortality attributable to poor modeling

By Pasi Autio

I can feel the heat…

New Study “The burden of heat-related mortality attributable to recent human-induced climate change” published on Nature Climate Change makes case that one-third of the heat-related deaths in many cities around the world can be attributable to Climate Change. A very strong claim indeed. The study has got wide publicity in high-profile media, such as in New York Times.

Study claims that heat-related deaths have increased by an average of 37.0% on 732 locations in 43 countries covered. 37.0% increase between 1991 and 2018.

The make such claim you would need to establish the following:

  1. Extreme temperatures have indeed increased on study locations
  2. Temperature increase during the study period is not due to other factors such as urban heat island effect
  3. Deaths have really increased during high-heat periods
  4. The increase of deaths is not due to increase of population
  5. The increase of deaths is not due to population average age being higher
  6. No other factors have an effect on deaths such as natural disasters

Let’s review how this study covers those questions to establish their case. Let’s start with temperature.

Study methods

Study analyses the data in two steps. First they generate association model between deaths and daily temperature:

As described in detail in the Methods, a first-stage model estimates associations for each
location, which are then pooled in a meta-analysis (the second stage). The observed temperature and mortality data were collected through the Multi-Country Multi-City (MCC) Collaborative Research Network, the largest weather and health data consortium to date (

They don’t provide the full dataset as a part of the supplemental data, but they do provide R-code and sample dataset. From the sample dataset we can see the following source data for each location:

Sample data from Supplemental material

Date, deaths and temperature. The basic assumption seems to be that high temperature directly affects the death rate. Hold on! Where is the population data or age distribution data? Such details seem to be considered as trivial information, which is not needed for state-of-art analysis.

In many countries the population within study location might have been increasing considerable already during the 10 years. And the same applies to percentage of senior citizens, which is increasing at the mortality rate on many study locations.

The second step they make is to establish “Climate Change”-related deaths value by:

In the second step, we used the estimated exposure-response
functions to compute the heat-related mortality burden between
1991 and 2018 for each location under two scenarios: a factual
scenario consisting of simulations of historical climate (all climate
forcings) and a counterfactual scenario where climate simulations
are driven by natural forcings only, thus approximating the climate
that would have occurred in a world without human-induced or
anthropogenic climate change

Really straightforward: Just assess the temperature – death-rate relationship and then consider how much the temperature has increased by using Climate Models. End-result is the percentage of deaths caused by Climate Change.

Straightforward and totally wrong. Instead of evaluating all factors listed earlier (1 to 7) they consider none of them. To prove the point, let’s analyze couple of locations in more detail.

Figure 5 from the study: Heat-related mortality rate attributable on human-induced climate change 1991-2018

The figure above is provided as a part of study. The analysis of all 732 locations would require considerable time and effort for data collection, so let’s concentrate on two countries, which are highlighted with high “Heat-related mortality rate attributed to climate change”.

Let’s start with Finland:

Heat-related mortality in Finland

Study finds Northern European country Finland and the capital city Helsinki to have high heat-related death rate. Really? Finland? My home country is not exactly known for high temperatures or long heat waves. Most of the Finns wait for decent summer temperatures, which is considered to be over 25 Celsius. There is even a Finnish word “helle” for this sunny summer weather and when the “helle” arrives, this is good news for majority of Finns every summer.

To make the case for increased temperatures, we first need to establish whether these “heat waves” have increased in Finland. For capital of Finland we have temperature data available between 1844-2021. Let’s count for days with temperature maximum of over 25 Celsius for each year:

Number of days annually when tmax => 25 Celsius. Data source: Finnish Meteorogical institute, open data

What we can see is no significant increase of => 25 days during the history of Helsinki Kaisaniemi data. Slight increase at the end does not significantly differ from 1940s. Also consider increased Urban Heat Island effect: Helsinki population is now much higher than in 1940s.

If you limit your study just to years 1991-2018, you might (incorrectly) attribute the increase of warm days to Climate Change.

So for Helsinki the point 1: “Extreme temperatures have indeed increased on study locations” is only partially correct.

How about the deaths?

To study the mortality I downloaded the following data from the Statistics Finland open data for years 1945-2020:

  • Total Population
  • Deaths during months of June, July and August
  • Deaths on other months
  • Population data for age groups over 85
  • Deaths for age group over 85

I calculated a trend of deaths happening on summer months (June, July and August) vs. all deaths during the same year. The percentage is extremely stable and even slight decreasing during years Nature study years 1991-2018 while considering that population in age group 85 years or older has increased 10-fold between 1945-2019. Elderly people tend to be more vulnerable to high temperatures, but this has zero effect on mortality.

Thus considering the points earlier:

  • Mortality during summer months have not increased in Finland – at all

In summary: Data does not prove any kind of increase of mortality during summer months.

Heat-related mortality in Spain

Spain is even more dark red in the Nature study being highly vulnerable heat-related increase of mortality.

Fortunately for Spain there is an another study available:

Achebak H, Devolder D, Ballester J (2018) Heat-related mortality trends under recent climate warming in Spain: A 36-year observational study. PLoS Med 15(7): e1002617. 

This study covers 47 major cities from Spain for summer months between 1980 and 2015. This study uses real mortality data and temperatures for this period – not just models as this Nature study does.

Did they find increasing mortality? No they did not.

Achebak H, Devolder D, Ballester J (2018), Figure 5

They did find increasing temperatures with the increase of 0.32 Celsius per decade. But the overall mortality rate is decreasing – heavily.

The temporal pattern of each cause of death was similar in men and women (S2 Fig), with a decline in the number of deaths from circulatory diseases and an increase in the number of deaths from respiratory diseases. Nevertheless, mortality decreased at a slower pace in women for circulatory diseases, therefore increasing the magnitude of the difference between women and men. Moreover, for respiratory diseases, mortality increased at a faster pace in women, therefore reducing the magnitude of the difference between women and men. 

 Achebak H, Devolder D, Ballester J (2018)

Blue and red lines in the figure presents time-varying annual RR curves based on summer 1984 (coolest summer of the period) and red line is based on year 2003 (hottest summer of the period). Mortality rate for similar temperatures is decreasing as a whole for the study period.

The study pointed to a strong reduction in cause-specific and cause-sex mortality RR associated with summer temperatures for the last three and a half decades and, with the exception of respiratory diseases (for men and women together, and for women only), downward trends in heat-attributable deaths. These results strongly support the hypothesis that the observed warming trend in summer temperatures in Spain has not been paralleled by a general increase in the mortality fraction attributable to heat, as a result of substantial decline in population vulnerability to warm temperatures.

Downward trend is spite of portion of people aged over 64 has increased considerably during the years. But why? Study also provides answer for this:

The general downward trend in mortality risks has been attributed by some investigators to socioeconomic development and structural transformations, such as improvements in housing and healthcare services , or even to specific public health interventions. The large socioeconomic advances that occurred in Spain during the last decades might have also contributed to this response, thus reducing the effect of mortality risks over time. For example, the gross domestic product (from €8,798 per capita in 1991 to €22,813 in 2009), the life expectancy at birth (from 77.08 years to 81.58), the expenditure in healthcare (from €605 per capita to €2,182) and social protection (from €1,845 per capita to €5,746), and the number of doctors (from 3,930 per million inhabitants to 4,760 per million inhabitants) have all largely increased in Spain. In addition, the use of air conditioning, which has been postulated as a major contributor to the reduction in heat-related mortality in the United States, has also experienced a strong increase in Spanish households within the analysed period (from 5.3% to 35.5%).

In summary: Adaptation. Spanish population have made considerable investments on air conditioning – because they can. Increasing income provides better means to manage the excess heat.

The same adaptation is also visible in the Nature study: Mortality curve starts increasing at higher temperature for locations where the excess heat is norm: Kuwait city, Bangkok etc. It’s difficult to argue any reason why this adaptation would not continue – and despite of possible Climate Change.


The methods used in A. M. Vicedo-Cabrera et all 2021 are seriously flawed causing results and conclusion to be invalid.

This rebuttal covered just two countries (Finland and Spain), but already this proves that:

  • There is no increased heat-caused mortality due to any reason and if there is no increase in mortality overall it is impossible for Climate Change to have any effect
  • All increases are due to flawed methods, which rely on Climate Models instead of real mortality data
  • Even then the study fails to mention any other factors affecting the mortality such as population aging and increase
  • Adaptation to excess heat is ongoing everywhere automatically when the increasing income allows it


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June 3, 2021 6:17 am

Peer reviewed was it? Presumably Greta liked it.

Peter W
Reply to  observa
June 3, 2021 6:28 am

Perhaps it was peer reviewed by Scientific American?

Paul S
June 3, 2021 6:35 am

What a bunch of poppycock

Bill Powers
Reply to  Paul S
June 3, 2021 1:38 pm

New Donner Party study indicates cannibalism is attributable to Global Cooling.

Right-Handed Shark
June 3, 2021 6:39 am

So, not so much a “study”, more a demonstration of how to lie with statistics. Next they’ll be telling us that they can calculate the average global temperature.

Reply to  Right-Handed Shark
June 3, 2021 7:47 am

It’s attribution statistics so it comes from the field of marketing.

Alan Watt, Climate Denialist Level 7
June 3, 2021 7:08 am

Is this the same study as this one, which concluded that:

Honolulu had the highest portion of heat deaths attributable to climate change, 82 percent.

This study was guest-pilloried by David Middleton June 1st.

Kevin kilty
June 3, 2021 7:08 am

I know that people will complain about peer-review here, but this study if reviewed by peers with the same care that our author took, and extended to the entire data set, would overwhelm a gaggle of reviewers. The peer-review process has many flaws indeed, even some level of corruption, but the worst in my opinion is that it is being expected to do the impossible.

Steve Case
Reply to  Kevin kilty
June 3, 2021 7:26 am

BINGO and that’s just for one study. Climate “Science” and a subservient media churn out a never ending stream of never ending bullshit.

Alan the Brit
Reply to  Steve Case
June 3, 2021 10:58 pm

Isn’t Climate Science a contradiction in terms?

Reply to  Kevin kilty
June 3, 2021 10:06 am

Agreed. I have been a reviewer on several occasions for natural science and decision analysis papers and regularly correspond with others that take on reviews in related fields. The amount of work required to properly review a complex article is well above what the average reviewer is willing to put in. This is most telling when 1 of 3 reviewers find basic yet fatal flaws in the methodology while the other 2 recommend it for publication or even commend the authors for ‘innovative’ methods (translation: methods they didn’t understand and/or bother to investigate).

Steve Case
June 3, 2021 7:19 am

John Brignell’s Warm List is no longer active, but articles like the heat-related mortality article from the New York Times belong there along with all the hundreds of others that claim things like global warming; causes our brains to shrink, increases teen age prostitution, tiger attacks, bubonic plague . . . etc. The so called mainstream media produces a never ending Gish Gallup of global warming bullshit that realistically would take an army of debunkers with no platform to do it from to take on the onslaught of propaganda that “President” Biden says is “The existential crisis of our time”

Reply to  Steve Case
June 3, 2021 8:55 am

The poor sod didn’t know what Herculean task he was taking on in compiling Swindler’s List.

Pasi Autio
June 3, 2021 7:22 am

After I wrote this essay, I found some additional points to consider regarding heat mortality in USA. Those where added to the story in my own blog:

Reply to  Pasi Autio
June 3, 2021 7:50 am

In real science you are obliged to consider every other option it is called the “look elsewhere effect”

What happens if you don’t do it you end up with data dredging which is the correct name for this study

However that is in real science in climate science you seem to be able to do whatever the hell gives the right answer.

Last edited 1 year ago by LdB
June 3, 2021 7:43 am

Extreme temperatures and health — European Environment Agency (

“In large parts of Europe, summertime temperature records, which are associated with prolonged heat waves, have increased substantially in recent decades. The summer of 2003 broke temperature records in large parts of western Europe; temperature records were again broken in different parts of Europe during the summers of 2006, 2007, 2010, 2013, 2014 and 2015. The record warm summer of 2003 was an outstanding example of increased mortality during periods of extreme temperatures, with an estimated premature mortality of 70 000 people in Europe. The heat waves of the summer of 2015 caused more than 3 000 deaths in France alone”

That’s not modelling, that’s observed results…

Reply to  griff
June 3, 2021 8:15 am

Yeah our study showed four out of five doctors say that if you don’t believe in climate science you will self combust and go straight to hell.

Now we have to confess it did take us a while to find the four doctors.

Reply to  griff
June 3, 2021 8:17 am

griff, the number of people that died in a localized, short duration heat wave almost two decades ago has absolutely no bearing on the question of how many deaths can be attributed to climate change. None. Do try to reread the 6 questions that the author succinctly summarized at the start of the article. If you are having trouble understanding them, reach down with both hands, grab your ears, and tug your head sharply in a downwards direction.

Reply to  griff
June 3, 2021 9:06 am

Wrong dealing with warm weather was the first and only reason people died.
Closed windows (let the heat outside), no ventilators, not drinking enough were the main reasons.
Blockong weather as in 2003 is not only due to climate change.

Climate believer
Reply to  griff
June 3, 2021 1:55 pm

How can you be so consistently dumb, so myopic?

I know you don’t listen to anyone, so this is just some context for others who might be reading this.

France, 1976, very severe heatwave, excess deaths 4540.

France, 1983, very severe heatwave, 42.5°C (108.5°F) in St-Raphaël, excess deaths 4700.

France 2006, very severe heatwave, excess deaths 2600.

France 2019, two very severe heatwaves, excess deaths 1435, 974 of those were over 75.

Alarmists love to point to 2003 as proof of something, but it is a complete outlier in France, and the high excess deaths were due to many other factors totally unrelated to the weather, which I might add have since been remedied.

Historically notable heatwaves in 1911 and 1947 as well, not to mention 1718 and 1719, but let’s leave it there…

Reply to  Climate believer
June 3, 2021 5:37 pm

I’m beginning to think griff is a fake, designed to make climate believers look bad.

Reply to  griff
June 3, 2021 2:01 pm

Where I currently live, the local max day temps for this time of year are 20 – 23C
Last 2 days + today we’ve had 26 – 27C.
So, our local weather presenter is now breathlessly telling us we’re having a “heatwave”.

If that’s the case, judging by the greatly increased number of people I see out & about in the parks & sunshine now, folks must just LUUURVE “heatwaves”.

Alan Watt, Climate Denialist Level 7
Reply to  griff
June 3, 2021 4:20 pm


The author already posted data for Finland and Spain which shows that simply isn’t true. Also not true for Hawaii, where supposedly 82% of “head related” deaths are attributed to climate change.

Alan Watt, Climate Denialist Level 7
Reply to  griff
June 3, 2021 4:37 pm

The record warm summer of 2003 was an outstanding example of increased mortality during periods of extreme temperatures, with an estimated premature mortality of 70 000 people in Europe.

[emphasis added]

That’s not modelling, that’s observed results…

Ah, no. By definition an “estimation” is not “observed results”.

The term “premature” mortality is also slippery. If someone dies an estimated 10.655 minutes sooner than they would have absent some presumed contributory influence, that is counted as “premature mortality”.

Reply to  griff
June 3, 2021 6:38 pm

And in 2018 more died on French roads (almost 3300 if you check their stats). What are you suggesting here griff? Elon will not be happy if you tell French Tesla owners they have to take the bus or train everywhere.

Reply to  griff
June 3, 2021 8:25 pm

I’ve addressed this before on this site. The 2003 “heat wave death event” was a full on lie.

You cannot reconcile the claimed deaths by the heat wave with actual death certificates. Apparently heat waves can kill more people than are recorded to have died!


Bruce Cobb
June 3, 2021 7:53 am

That woman in the photo above appears to have the Climate Vapors. This is a relatively recent affliction, characerized by feelings of doom due to imagined “carbon pollution”. Sufferers typically lack an ability to use reason or logic, and innumeracy. In the past, they have been derided as “climate bedwetters”, but this is false as well as mean. They haven’t done that since they were very young. The affliction appears to be widespread, as well as self-reinforcing. Much further study is needed, however.

Rick W Kargaard
June 3, 2021 7:54 am

The goal seems to be to instill a fear of heat.
Environment Canada has included a heat warning in forecasts of 30C for the last couple days in my area of the world.
My response, I drank a few beer in the shade with pleasant company, I delayed my evening meal until a cooler part of the day, I turned on the fan in my bedroom for a couple hours at sleep time (I likely would not have bothered with the fan but it is Alexis controlled so no need to get up.)
At no point was air conditioning required or used but probably would have been nice in my car in city traffic.
I am nearing 80 years of age so am presumably more vulnerable to heat stress. It would, however, probably take another 10 degrees to move me out of my comfort zone. My response to that, more ice in my drink, less time in the sun, and perhaps a little use of air conditioning.
I am likely in more danger of becoming anemic through blood loss due to mosquito predation.
It should be noted that this was a predicted maximum temperature which is typically reached for only a few hours in mid-afternoon.
It is difficult to take these types of warnings seriously.
It is extremely difficult to understand why our government wants a cooler Canada. These few warm (not hot) days are welcome after a cool April and May.

Reply to  Rick W Kargaard
June 3, 2021 9:15 am

Indeed Rick … I am in Calgary and years ago I read a breathless report about the worst case for GLO-BULL warming in S Alberta & we could end up with a climate like Kentucky … we all know that life in Kentucky is impossible due to the extreme climate 😉

Rick W Kargaard
Reply to  stewartpid
June 3, 2021 11:07 am

Yes, There is a reason that swimming pools are a rarity around here but hot tubs are common. It might be a clue as to our climate. A warmer climate would suit me just fine.

June 3, 2021 8:00 am

Did they find headlines? Yes they did.

Ron Long
June 3, 2021 8:05 am

Wow! The CAGW crowd is a bunch of fools in a hurry. Remember the Jim Croce song, about the underage girl: “Like a fool in a hurry I took her to my room. She casted me in plaster while I sang her a tune”. Shortly thereafter Jimbo spends ten years in prison. The CAGW crowd needs to be put somewhere so they can contemplate reality for awhile.

June 3, 2021 8:19 am

Once a model was a pretty girl…

H. D. Hoese
June 3, 2021 8:29 am

Last line in abstract, don’t even try to hide their advocacy. “Our findings support the urgent need for more ambitious mitigation and adaptation strategies to minimize the public health impacts of climate change.”  Obviously done by a committee, 31 citations, earliest 2006, rest were in last 12 years. When was the big pollution mortality in London? A generation ago the assumption would be that they did, nowadays who knows?

One author shows these affiliations, quite a range of expertise. I used to think that I ventured too widely at times, but never suggested controlling humanity or any part thereof. — Department of Public Health, Environments and Society, London School of Hygiene & Tropical Medicine, London, UK; The Centre on Climate Change and Planetary Health, London School of Hygiene & Tropical Medicine, London, UK; Centre for Statistical Methodology, London School of Hygiene & Tropical Medicine, London, UK

This makes it easier to mistrust the “science” as proven by the recent debacle, thank goodness for the real doctors doing the real work.

Reply to  H. D. Hoese
June 3, 2021 9:34 am

“Our findings support the urgent need for more ambitious mitigation and adaptation strategies to minimize the public health impacts of climate change.”

Science is If A then B. It is not If A then B so we must do C. C is a political question that should be answered by democratic means.

Peta of Newark
June 3, 2021 8:38 am

I iz in March today (cryptic), no matter, except here are a few words of ‘mine host’

I cannot find an easy way to link to the relevant pages of his ‘document’.
Could copy/print the relevant and put on Dropbox but that’s probably naughty, the author would not mind, tedious little nobodies would

Go here then follow his link to ‘Summer Magazine‘ and look for ‘Does truth Matter?
If you open in your browser = Page 7 of the pdf, or Pages 4 & 5 of the magazine

M Courtney
June 3, 2021 11:41 am

If the paper was any good it wouldn’t be in Nature Climate Change.

Jeffery P
June 3, 2021 12:01 pm

Our modern world puts too much emphasis on models. One should always remember models do not output facts or data. The results from models are predictions, nothing more. The predictions will show the validity of the model when results are compared to actual measurements.

June 3, 2021 12:27 pm

How much is a bogus publication worth over time in contribution to annual academic raises, attaining tenure, conference travel, and long term retirement earnings. Let’s model it.

Michael in Dublin
June 3, 2021 2:27 pm

When observations and models contradict one another the alarmists go with the models and adjust the recorded data to fit their models. Proper science follows observations, politics the models.

June 3, 2021 2:30 pm

As if the increased cost of energy hasn’t contributed to loss of life by normal temperature changes of seasons. Better living conditions against weather have increased longevity in every country that have more access to electricity.

Tom Abbott
June 3, 2021 4:59 pm

From the article: “What we can see is no significant increase of => 25 days during the history of Helsinki Kaisaniemi data. Slight increase at the end does not significantly differ from 1940s. Also consider increased Urban Heat Island effect: Helsinki population is now much higher than in 1940s.”

It appears it was just as warm in Helsinki in the Early Twentieth Century as it is today, according to that chart.

Another example showing that we are not experiencing unprecedented warming today, due to CO2 (or anything else), as the Alarmists claim.

There are numerous other examples from around the world that show the very same temperature profile as Helsinki, i.e., it was just as warm in the recent past as it is today even though there is more CO2 in the atmosphere today than back in the 1930’s.

No unprecedented warming today means CO2 is a minor player in the Earth’s climate and is not a problem that needs to be addressed by the governments of the world.

Last edited 1 year ago by Tom Abbott
June 3, 2021 11:29 pm

The “study” also misuses temperature. Temperature is generally measured in whole numbers. You MUST retain the same degree of precision with averages.

June 5, 2021 8:47 pm

Well to do the study right you have to adjust for increased use of AC. So calculate the number of deaths adjusting for the other factors you mentioned, then add back in the number of people whose lives were saved by air conditioning.

Why add to the death toll lives saved by AC? Because AC is bad and they shouldn’t be using it, and it will make the numbers closer to what the authors wanted.

Pasi Autio
Reply to  Kazinski
June 6, 2021 12:06 am

The numbers authors used where modelled and did not reflect the real mortality figures at all.

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