r pollution, the [scientific] literature is much larger, so no one questions that air pollution is toxic and kills. This sort of messaging for heat is more recent.”
There are, broadly speaking, two approaches to calculating deaths during a heatwave.

The first involves counting the number of excess deaths relative to a period in the past.

This method – often referred to as an “excess deaths” approach – looks at how many people died during a particular time period compared to a baseline period where there was no heatwave.

To do this, public health authorities and researchers rely on official death figures reported by country authorities.

The heat death tolls published in recent weeks by public health agencies in Belgium, France, Germany and the Netherlands relied on this approach.

(For more, see: What are the pros and cons of the ‘excess deaths’ method?)

The second method uses long-term mortality data to understand the statistical relationship between temperature and mortality in a given place. The model that emerges can be used to infer the number of deaths from a heatwave in that place.

In a rapid analysis published this week, researchers at Imperial College London, the London School of Hygiene and Tropical Medicine (LSHTM) and the Met Office used this approach to estimate that the May and June heatwaves in the UK caused the deaths of 2,700 people.

Dr Callahan – working with Prof Andrew Dessler, director of the Texas Center for Extreme Weather at Texas A&M University – used this method to estimate that more than 2,700 people had died in France over a 17-day period in June in an analysis for Carbon Brief.

(For more: see: What are the pros and cons of the ‘statistical modelling’ method?)

The majority of the figures released in the wake of Europe’s June heatwave have relied on these two methods.

There is a third way to calculate heat deaths, which is to look at official counts of deaths attributed on death certificates to heatstroke.

Callahan tells Carbon Brief that the “death-certificate coding” appears to have fallen out of favour in Europe – which he says is a “smart move” given that it does not provide a “full accounting”.

Nevertheless, some public health authorities are still using this method. For example, in the wake of the heatwave in the US earlier this month, public health data showed 29 people in New Jersey and three people in New York had died[...]

from “heat-related illnesses”.

Scientists tell Carbon Brief the excess deaths and statistical modelling approaches both have advantages and drawbacks. These are explored below.
What do the latest figures show for Europe’s May and June heatwaves?

The table below shows the death numbers that have been reported by governments and researchers for Europe’s May and June heatwaves, including the approach used to reach the figures.

It suggests that multiple countries in Europe experienced more than 1,000 heat-related deaths during the late June heatwave, with authorities in Germany counting more than 5,000.

Meanwhile, the EuroMoMo mortality monitoring system estimated there were more than 10,500 excess deaths across 27 countries during the June heatwave.
ReportedSourceCountry / regionDatesDaysDeathsLinkApproach 28/06/2026Public Health France ​France22-27 June61,000santepubliquefrance.fr Excess deaths 29/06/2026World Health OrganizationEurope21-28 June81,300x.com/DrTedros/status Excess deaths 01/07/2026Carlos III Health Institute (MoMo)Spain1-30 June301,033dw.com Excess deaths (all-cause and temperature-attributable) 02/07/2026National Institute for Public Health and the EnvironmentNetherlands22-28 June7480rivm.nl
Excess deaths 03/07/2026Public Health France ​France22-28 June72,025santepubliquefrance.fr Excess deaths 07/07/2026Chris Callahan/Andrew DesslerFrance12-29 June182,766carbonbrief.org Statistical modelling 08/07/2026Chris CallahanEurope15-28 June1413,975zenodo.org Statistical modelling 08/07/2026SciensanoBelgium18 June - 1 July141,747brusselstimes.com

Excess deaths 09/07/2026Robert Koch InstituteGermany22-28 June75,120rki.de Statistical modelling 13/07/2026Met Office/LSHTM/ImperialEngland and Wales22-27 June62,183drive.google.com Statistical modelling 13/07/2026Met Office/LSHTM/ImperialEngland and Wales24-26 May3553drive.google.com

Statistical modelling 13/07/2026EURO Mo/Mo27 European countries22-28 June710,650reuters.com Excess deaths 07/07/2025National Institute for Public Health and the EnvironmentNetherlands22-28 June7577archive.ph

Excess deaths 14/07/2026Germany Federal Statistical Office (Destatis)Germany22-28 June75,753destatis.de
Excess deaths
In most instances, Carbon Brief has linked to the figures published [...]

by public health authorities, where numbers were first reported. In some instances, figures were released on dashboards or webpages that are updated weekly. In these cases, Carbon Brief has linked to media reports or archived web content.
What are the pros and cons of the ‘excess deaths’ method?

The excess deaths approach looks at how many more people died during a particular time period compared to a baseline period of the same length.

For instance, on 14 July, Germany’s federal statistics agency, Destatis, published figures showing Germany saw 32% more deaths than the average in the week of 22-28 June, which was dominated by the heatwave.

Specifically, the agency said that 23,932 deaths had been recorded that week, compared to an average of 18,179 in that calendar week across the years 2022-25.

This suggests there were 5,753 excess deaths during the heatwave week. (This was a slight increase from preliminary Destatis figures released a week earlier, covered by Bloomberg.)

The Netherlands similarly calculates excess deaths by comparing death figures against an average of deaths in a similar period during unspecified “previous years”.

Data published by the country’s National Institute for Public Health and the Environment (RIVM) shows that, during the week of 22-28 June, an estimated 3,626 people died in total in the northern European country.

This is 577 more deaths than the 3,049 expected at that time of year, it said. (This is a slight revision upwards from the 480 excess deaths reported on 4 July by NL Times based on preliminary figures from NVIM.)

Callahan says that the excess deaths approach has the benefit of being rapid and relatively uncomplicated:
“It is something that public health authorities can put out fairly quickly without having to run a fancy model and do coding like the academic scientists do. It is a short-term, high-impact, rapid estimate of mortality.”
The drawback to the approach is that it is impossible to decipher what percentage of these “all-mortality” excess deaths are, in fact, heat-related.

Imperial College’s Konstantinoudis notes that the public often “feels more comfortable” with the excess deaths approach over the statistical modelling approach because the data it is using – the official death numbers – is based on real-world data.

However, he stresses that excess deaths figures are based on a series of assumptions, including the reference period picked by researchers and how the numbers are interpreted.

Statisticians and researchers have to make a series of decisions, including what period to use as a comparative baseline. For example, the baseline period could be the week before a heatwave, the same week a year before – or an average of the same week across multiple years in the past. If averaging mortality of a similar period across a number of previous years, they must decide how much “weight”, or influence, each year should have.

They must also decide how to account for spikes in deaths during the Covid-19 pandemic years, as well as the gradual rise in average temperatures due to global warming.

During the pandemic, many governments and the World Health Organization (WHO) used the excess deaths approach to count deaths. The WHO said this metric was more “comparable” and “objective” than relying on national reports of Covid-19 deaths,[...]

given that different countries used different criteria for this classification.

A notable example of how assumptions can skew excess death figures came during this period, when the WHO estimated in 2022 that Germany had seen 195,000 excess deaths over two years of pandemic.

However, after statisticians and epidemiologists pointed out the assumptions in the model were not suited to Germany’s demographics, the WHO retracted the figure and eventually reduced it to 122,000 and then later to 102,000.

Konstantinoudis explains:
“Covid taught us that it is complicated. Depending on the different assumptions used in the excess-mortality approach, you get different results…There is a scientific basis, but we should acknowledge the assumptions.”
What are the pros and cons of the ‘statistical modelling’ method?

In the statistical modelling approach, researchers use models to determine the specific relationship between mortality and temperature for a particular location and then apply it to temperatures observed during a heatwave.

This allows them to estimate the overall number of deaths that were caused by a heatwave.

Previous research has revealed that, in most places of the world, there is a U-shaped response of mortality to temperature – where deaths increase rapidly in cold or hot conditions as daily maximum temperatures depart further from an “optimum temperature”.

For example, research published in Proceedings of the National Academy of Sciences in 2025 found that mortality rates in France rise as daily maximum temperatures move away from approximately 20C. This is shown in the chart below.

https://www.carbonbrief.org/wp-content/uploads/2026/07/Screenshot-2026-07-16-at-16.48.57-1024x931.png Relationship between daily high temperature and all-cause mortality rates in France, estimated using data over 2004-19. Credit: Dr Christopher Callahan, based on data and methods in Callahan et al. (2025)

Indiana University’s Callahan say this approach allows scientists to “formally establish a relationship between the temperature and the mortality”, adding:
“If you do these calculations right, you can credibly say your entire estimate of mortality is heat-related.”
Prof Antonio Gasparrini, biostatistician and epidemiologist at LSHTM, explains the method relies on “timeseries models that apply relatively sophisticated statistical methods in which you ‘smooth’ trends occurring in time, so you control for long-term trends and seasonality”.

He says that these models also allow researchers to “remove” trends affecting mortality that are unrelated to heat – for instance, the impacts of the pandemic. They can also “add” other information, such as around how air pollution combines with heat to threaten vulnerable populations.

Gasparrini adds:
“What statistical modelling can bring is that it is more refined. It can link specific temperatures to specific impacts rather than just looking at the event [in the whole]. And also, it can be localised – [data] can be stratified at a fine scale and we can look at impacts at different scales.
“So, it is more informative. But, at the same time, of course, it’s based on more assumptions than the [excess deaths approach] and, of course, needs to be checked and compared.”
The approach depends on a number of judgment calls from scientists and statisticians, including the years picked to under[...]

pin the model and how to capture the lag in deaths in the days and weeks after a heatwave event.

They must also decide at what threshold to start counting deaths – in other words, whether to count all deaths above the “optimum temperature” or set a higher, more extreme value – and whether and how to account for any adaptation to heat extremes that may have been put in place in the study area.

A benefit of the statistical modelling approach is that it opens the door for being able to attribute a specific number of deaths to human-caused climate change.

By applying the temperature-mortality curve to both the temperatures of the recent heatwave and a counterfactual world without climate change, scientists can estimate what proportion of estimated deaths only occurred because the world is warming.

For instance, Imperial College, LSHTM and Met Office researchers found that 59% and 38% of heat-related deaths in the UK’s May and June heatwaves, respectively, could be attributed to climate change. Their findings are shown in the chart below.
https://www.carbonbrief.org/wp-content/uploads/2026/07/heat-wave-death.png Number of heat deaths in England and Wales over 21-29 May and 18-28 June attributable to climate change. Source: Barnes et al (2026).
Some climate-sceptic commentators have argued that modelled estimates are hypotheses and should therefore be treated with caution.

On 13 July, climate-sceptic news website GB News covered a blog post by Oxford academics that argued the figure that 2,700 people had died in the UK’s May and June heatwaves was not reflected in the provisional “all-mortality” data put out by the UK’s Office for National Statistics (ONS). Quoting the blog, GB News said:
“Modelling tells us nothing. Models explore possibilities; surveillance tells us what happened. When the two disagree, our instinct should be to investigate the data rather than simply trust the model.”
However, Imperial’s Konstantinoudis – who worked on the models behind the 2,700 figure – says it is important to await the UK Health and Security Agency (UKHSA)’s annual heat mortality report before arriving at any conclusions. He explains:
“While we are entirely clear that our current findings are modelled estimates, this methodology has consistently delivered comparable results to the UKHSA’s own official analyses of observed deaths for past heat events.”
(The UKHSA report will include updated figures and estimate excess deaths from heat based on specific periods of heat in different regions, whereas the provisional ONS figures cover all national deaths during a full-week period.)

Konstantinoudis says both the excess deaths and statistical modelling approaches have been the subject of extensive peer-reviewed scientific study and can provide a “holistic view of what is happening” when used together.

Studies that have compared statistical modelling approaches for estimating heatwave deaths with excess death figures in the UK have found they yield broadly similar results.
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The post Q&A: Europe’s May and June heatwave deaths – and how they were counted appeared first on Carbon Brief.

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NEW – Q&A: Europe’s May and June heatwave deaths – and how they were counted

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Debriefed 17 July 2026: UK ‘firewave’ | Fossil-fuelled heat deaths | London’s Natural History Museum spotlights climate
Welcome to Carbon Brief’s DeBriefed.
An essential guide to the week’s key developments relating to climate change.

This week

Heat and firewaves

‘FIREWAVE’: Wildfires ravaged Europe and North America this week. France utilised water-dumping planes collecting from the Seine to contain a fire in the Fontainebleau forest near Paris, according to the Associated Press. The Financial Times reported that the UK has had “25 non-consecutive days with temperatures of 30C or more, including nine days above 34C”, creating a “firewave” and putting pressure on emergency services. Meanwhile, an “orange haze from Canada wildfires” could be “seen in Ontario and northern US”, said BBC News.

‘NEW NORMAL’: Climate events previously seen as extreme are becoming the “new ‘normal’”, said the Met Office, in a report on the UK’s climate. While last year was the UK’s hottest on record, rising temperatures mean it is expected to be surpassed in the next few years, reported Reuters. Liz Bentley, head of the Royal Meteorological Society, told the Guardian that “climate change has been described by scientists for many years but is now increasingly being felt by the UK population in their own homes and communities”.

Around the world
* ELECTRIFYING PUSH: The European Commission has announced a target for electricity to account for 46% of energy consumption across the bloc by 2040, reported Carbon Pulse. The commission has also made plans to adapt its emissions trading system to “bring relief to industry”, it said.
* FALLING OIL: The International Energy Agency said that global oil demand is expected to decline this year for the first time since 2020, reported the Associated Press.
* US ROLLBACKS: Trump cuts to clean energy support “led to the cancellation ​or delay of $83bn in investment across hundreds of projects”, reported Reuters. The Trump administration has also changed environmental law to allow development in the habitats of endangered species, according to CNN.
* BURNHAM BEGINS: Incoming UK prime minister Andy Burnham is preparing to announce new North Sea drilling “within days of taking office”, said Bloomberg. Carbon Brief looked at 28 statements that Burnham has made about climate change and fossil fuels.
* DRY JULY: Drought in Uganda led to significant crop losses and at least 16 deaths from starvation, said BBC News.
* ON AI: Australia planned to imp[...]

lement restrictions on energy and water usage for datacentres “amid [an] AI boom”, said the New York Times.
38%

The drop in Brazilian Amazon deforestation in the first half of 2026, compared to last year, reported Al Jazeera.
Latest climate research

* The area of land burned by wildfires in Africa each year has reduced due to a shrinking dry season | Geophysical Research Letters
* Most people do not distinguish between climate adaptation and mitigation when thinking about tackling climate change | Climate Outreach
* An “effort-sharing framework” has been developed to support progress towards the Paris Agreement | npj Climate Action

(For more, see Carbon Brief’s in-depth daily summaries of the top climate news stories on Monday, Tuesday, Wednesday, Thursday and Friday.)

Captured
https://www.carbonbrief.org/wp-content/uploads/2026/07/heat-wave-death-SOCIAL.png
Carbon Brief explained how more than 1,000 heat-related deaths in England and Wales during May and June were attributed to climate change, accounting for almost half of all heat-related deaths experienced during those months. The article also unpacked the different methods for estimating heat deaths around the world.

Spotlight

Natural History Museum exhibits climate change

This week, Carbon Brief interviews Meaghan Macdonald, senior project and programme manager for London’s Natural History Museum, about their first permanent climate-themed exhibition, Fixing Our Broken Planet.

Carbon Brief: Why are programmes such as Fixing Our Broken Planet so important?

Meaghan Macdonald: One of the main things we’re trying to achieve with Fixing Our Broken Planet is to place the museum as a convener of conversations around the planetary emergency…trying to bring together the different groups of people who need to be involved in this conversation in order to work together to find a solution.

And we find that a lot of the people who come into the gallery weren’t necessarily coming here to see it; they come across it, which is a really great way to engage people who may not have been engaged in that discussion previously.

CB: How does the exhibition engage and inspire visitors?

MM: A driving force for this exhibition is that you are dealing with a subject matter that can be quite disheartening, and one of the things that we were very careful about is to try to make sure that woven throughout the scientific data… is a sense of hope… to enable people to feel empowered to make a[...]

difference.

We were able to do things like our “what you can do” labels, which give an example that people can take away with them. We also have “conversation starters”, which is a digital screen that asks people a series of questions related to the planetary emergency. Things like: “Should we mine the deep sea to power the green economy?”…And there’s no right or wrong answer.

We [also] set out very specifically to…forefront the science that’s happening here. We know from multiple studies from thinktanks and organisations that people actually trust our scientists the most.
https://www.carbonbrief.org/wp-content/uploads/2026/07/3ABF3A0-1024x682.jpg Natural History Museum’s Fixing Our Broken Planet exhibition. Credit: Micheal Melia / Alamy Stock Photo
CB: The museum has set out a goal to “create advocates for the planet”. What does this mean? How does it relate to the exhibition and the museum’s wider climate action?

MM: The aim of the museum is to get to a place where both people and the planet thrive. Being a library of the natural world, it is our duty to be standing up for it and to help people find their way, fighting for nature’s side.

In order to create those advocates, the aim of the [exhibition] and the wider advocacy programmes at the museum is to try to find ways to bring all these people [individuals, policymakers, industry, scientists] together.

We have the wider programme with Fixing Our Broken Planet. We have Generation Hope…a free graphic panel version of our display in the gallery that we have been able to get into a number of venues in Bangalore…the very long-standing and beloved wildlife photographer of the year [exhibition]…our urban nature movement…[and] an initiative that we are doing with the Department for Education called the National Education Nature Park.

Watch, read, listen

STUBBORN HOPE: For the Conversation, climate scientist Prof Peter Stott argued that researchers need to “talk more about the very worst-case scenarios” and the possibility for action.

EXTREME: Vox’s the Gray Area podcast spoke to New York Times journalist David Wallace-Wells about the possibility of a “Godzilla” El Niño.

RESPONSIBILITY: For Climate Home News, two researchers from the Center for International Environmental Law explored how “major emitting countries knew of climate risks decades earlier than claimed”.

Coming up
* 13-31 July: Meeting of t[...]

he International Seabed Authority assembly and council, Kingston, Jamaica
* 17-19 July: 3rd International Conference on Environment and Sustainable Development, London
* 19 July: Presidential election, São Tomé and Príncipe Pick of the jobs
* Zero Carbon Analytics, research lead | Salary: Unknown. Location: Remote
* Met Office, ocean climate scientific manager | Salary: £54,515-£58,582. Location: Exeter
* National Trust, land use and nature delivery partner | Salary: £44,499. Location: Newcastle or York DeBriefed is edited by Daisy Dunne. Please send any tips or feedback to debriefed@carbonbrief.org. This is an online version of Carbon Brief’s weekly DeBriefed email newsletter. Subscribe for free here.
<picturehttps://www.carbonbrief.org/wp-content/uploads/2023/06/debriefed_HERO_BLANK-1550x1033-1-300x200.png DeBriefed 10 July 2026: Deadly Europe heat | EU electrification leak | COP31 president interview
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Jess Milligan

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Glossary: Decoding how China talks about energy and climate change | @Wanyuan_Song @xiaoying_you #CBarchive

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DeBriefed: UK ‘firewave’ | Fossil-fuelled heat deaths | London’s Natural History Museum spotlights climate

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Guest post: France’s June heatwave caused more than 2,700 heat-related deaths

✍️ Written by Christopher Callahan and @AndrewDessler

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Interactive: The pathways to meeting the Paris Agreement’s 1.5C limit | Uta Kloenne, Dr Debbie Rosen, Gaurav Ganti, Dr Alexander Nauels, @CarlSchleussner @joerirogelj @piersforster @rtmcswee @CONSTRAIN_EU #CBarchive

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Recommended read: For the Conversation, climate scientist Prof Peter Stott argued that researchers need to “talk more about the very worst-case scenarios” and the possibility for action.

https://t.co/UpnaOn2ebh

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Guest post: The conflicting practices in using land to tackle climate change | @evecologist #CBarchive

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