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Restoring tree cover is now firmly established as a strategy for removing carbon from the atmosphere to help tackle climate change.

But there is an elephant in the room when it comes to estimating just how promising a climate solution it is in different locations. This is “albedo” – the fraction of the solar radiation that is reflected from the Earth’s surface.

In essence, brighter surfaces – such as a large snowy expanse or a grassland – will generally reflect a high proportion of sunlight back into space. Trees, meanwhile, tend to be darker coloured and absorb more sunlight, keeping it on Earth – usually in the form of excess heat.

Because restoring tree cover often involves replacing brighter land covers – such as grasslands – with darker ones – namely, trees – this can lead to some degree of global warming.

In some locations, this warming can partially or even completely outweigh the benefit of increased carbon uptake by the trees. Many know of this problem, but it has been difficult to quantify the impact of albedo in specific locations. 

In our new study, published in Nature Communications, we map albedo change from restoring tree cover and show that carbon-only estimates of the global climate benefits of tree-planting may be 20-81% too high.

Our maps reveal that the climate benefits of tree-planting in savannahs in Africa and central Asia would be the most reduced by albedo. But we show that it is possible to find places that provide net-positive climate mitigation benefits in all biomes.

Tree cover affects albedo

It is getting harder to ignore albedo when planning projects to restore tree cover for climate mitigation.

For example, a recent study published in Science showed that albedo, among other factors, could substantially reduce the climate mitigation benefit of restoring tree cover.

However, despite its importance, albedo is often only given a brief mention as an important factor in research attempting to quantify the climate benefits of restoring tree cover. Its impact is frequently not accounted for – or only via coarse adjustments.

In some places, restoring tree cover modifies albedo enough to dwarf smaller changes in carbon, leading to an overall (net) increase in global warming. In other locations, the impact of albedo does not outweigh the carbon removal, contributing to an overall global cooling effect.

Understanding and quantifying these variations in albedo and carbon change is crucial to the success of a project that aims to restore tree cover for climate mitigation.

Yet there has been a lack of tools to provide this information. Our study sets out to change that.

Mapping albedo change

Our study provides the maps that quantify the absolute and relative changes in albedo anywhere on Earth where we might grow trees.

We first created a series of 24 maps that quantified how albedo would change if an area transitioned from one of four open land cover classes – such as grassland or croplands – to one of six different forest-cover classes, such as deciduous broadleaf or evergreen needleleaf forest. These are useful for individual projects that know their starting and end conditions.

Glossary
CO2 equivalent: Greenhouse gases can be expressed in terms of carbon dioxide equivalent, or CO2e. For a given amount, different greenhouse gases trap different amounts of heat in the atmosphere, a quantity known as… Read More

However, to examine general global patterns, we used a data-driven approach to model the albedo change resulting from the “most likely” open-to-forest transition for each part of the world. We then combined that with a map of maximum potential carbon storage to map net climate impact in carbon dioxide equivalents.

In this map (below), red and orange shading indicates regions where restoring tree cover leads to net warming and blue indicates regions where restoring tree cover leads to net cooling.

Map showing the net climate impact of tree-planting, accounting for both albedo change and carbon storage to estimate maximum climate mitigation in carbon dioxide equivalents (CO2e) per hectare.
Map showing the net climate impact of tree-planting, accounting for both albedo change and carbon storage to estimate maximum climate mitigation in carbon dioxide equivalents (CO2e) per hectare. Red and orange shading indicates regions where restoring tree cover leads to net warming, while blue indicates regions where restoring tree cover leads to net cooling. Source: Hasler et al (2024).

The map shows that, in many places, increasing tree cover is likely to contribute to global warming. These include the dryland ecosystems of central Asia and the Sahel region of Africa, as well as northern reaches of North America, Europe and Asia.

However, all biomes had at least some climate-positive locations, indicating that the coarse exclusions used in the past have missed opportunities. Moreover, some locations experience little to no albedo change, such as in south-east Asia, central Africa and the Amazon.

This map makes it possible for people to determine the best places to restore tree cover to achieve climate mitigation, as well as evaluate different scenarios of where restoration of tree cover might happen.

For example, we examined three previously published global studies of large-scale increases in tree cover. We find that, after accounting for albedo, the global climate mitigation benefit of restoring tree cover may actually be 20-81% lower than expected from carbon-only estimates.

Notably, the study with the greatest deduction included large areas of tree-planting within the tundra and other locations where we predict very negative climate outcomes. We show that constraining this study’s tree-planting to only the more climate-positive areas – about a third of the total area (311m hectares instead of 889m hectares) – would lead to a 2.5-fold increase in mitigation potential.

This demonstrates the value of strategic project placement to maximise climate benefit, because it is possible to achieve more mitigation with less investment of space.

Forest restoration projects

Encouragingly, our study also finds that hundreds of thousands of on-the-ground tree-planting projects tend to be concentrated in places where the potential for carbon removal is high and albedo change is moderate.

One example is the moist tropical ecosystems in Brazil and Indonesia. Most of these on-the-ground projects can be found at Restor, a data-driven and community-based platform that aims to accelerate restoration and makes it possible for the first time to evaluate outcomes of the global restoration movement.

This suggests that ongoing or planned projects are concentrated in places that are good for achieving climate mitigation. However, the majority – around two-thirds – of these on-the-ground projects still face an albedo offset of at least 20%, indicating that most – if not all – projects should consider albedo change in their accounting.

None of this is to criticise projects that fall in places with negative climate outcomes. There are many wider reasons for restoring tree cover in a given landscape, beyond climate mitigation, including cleaner water, wildlife habitat, stabilised soils, sustainable livelihoods and cooler local temperatures.

However, for projects where the emphasis is on achieving climate mitigation, it is important to consider changes in albedo alongside changes in carbon removal, especially now that the tools are available to do so.

Workers plant trees at the afforestation area by the Yarlung Zangbo River in China's Tibet Autonomous Region.
Workers plant trees at the afforestation area by the Yarlung Zangbo River in China’s Tibet Autonomous Region. Credit: Alamy Stock Photo

In general, climate accounting is not for the faint of heart. There are many factors such as albedo that can alter the total climate mitigation of natural climate solutions. However, we are in a critical time when pragmatic decisions need to be made now about which climate solutions to deploy and where.

Alongside our study, we have produced a dedicated web platform – called “naturebase” – to help policymakers, practitioners, communities and governments identify where, why and how to implement nature-based projects with the highest carbon mitigation.

This tool includes maps, data and case studies to show how different natural climate solutions – including restoration of tree cover – could benefit the climate across the world.

Policymakers and land managers are under growing pressure to make complex choices in line with global agreements. We hope that the science in our study and the tools in the naturebase platform will help enable smarter, more nature-positive decisions.

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Ugandan farmers launch UK court case against East African oil pipeline

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Four Ugandan farmers filed a case with London’s High Court on Tuesday, aiming to stop the East African Crude Oil Pipeline (EACOP) from starting to operate by asking the court to apply Uganda’s laws against the project’s UK-registered company.

The controversial 1,443-kilometre (897-mile) pipeline, majority-owned by French energy company ​TotalEnergies, aims to carry crude from Ugandan fields for export through neighbouring Tanzania. About 80% has been built so far, according to its developers.

The pipeline’s first oil exports are expected as soon as October, according to its developers, and the campaign group Avaaz, which is backing the farmers’ crowdfunded lawsuit, called it “one final chance to stop one of the worst oil pipelines on the planet”.

The claim, filed by London law firm Leigh Day, argues that EACOP Ltd’s role in developing and operating the pipeline breaches Ugandan laws that protect citizens’ right to a clean and healthy environment.

    One of the claimants, Racheal Tugume, told a press conference she had been displaced from her land due to the pipeline’s construction, which she said had damaged local rivers, wildlife and ecosystems that communities depend on for their livelihoods just as erratic weather linked to climate change takes an increasing toll.

    “I am very happy that there are people in countries like the UK who are listening to us, who are behind us and who have come to support us,” Tugume said, adding that she hoped the case would bring justice to communities affected by the pipeline.

    Ugandan law in UK court

    While the pipeline is a joint venture led by TotalEnergies, with smaller stakes owned by Ugandan, Tanzanian and Chinese national oil firms, it is operated by EACOP Ltd, a company registered to an office in London’s Canary Wharf financial district.

    EACOP Ltd did not respond to a request for comment.

    The claim appears to be the first attempt to have Uganda’s climate and environmental protections enforced in a foreign court, partly reflecting concerns over whether cases challenging the multibillion-dollar pipeline would get a fair trial in Uganda.

    Ugandans living near new oil pipeline let down by compensation programmes

    Concerns about access to a fair hearing are among the issues the court will consider when deciding if it should take on the case, said Matthew Renshaw, partner at Leigh Day.

    Renshaw said that precedents including the Nigerian oil pollution case against Shell have shown that claims against British-registered companies for harms overseas can be successfully fought in UK courts.

    “We are proud to represent the four brave principled individuals,” Renshaw said.

    Constitutional protections

    The pipeline project has already been subject to repeated lawsuits in several countries, none of which have succeeded. A climate lawsuit filed in Uganda more than a decade ago by a group of young people has yet to conclude. Another at the East African Court of Justice, brought by campaign groups against Uganda and Tanzania, was rejected on procedural grounds last November.

    A separate ongoing lawsuit in TotalEnergies’ home country of France – a refiled version of an earlier failed claim – cannot stop EACOP going ahead, but it does seek damages from TotalEnergies for affected communities.

    With the newly launched case, Leigh Day’s legal adviser Marc Willers said the claim draws on specific Ugandan laws in a bid to stop EACOP’s operations.

    Uganda may see lower oil revenues than expected as costs rise and demand falls

    These include the Ugandan constitution, a 2019 environmental law and the National Climate Change Act 2021, which gives Ugandans the right to bring a case before a court in circumstances where anyone or any entity threatens the country’s ability to mitigate climate change.

    Stopping a “carbon bomb”

    The pipeline, which will link Uganda’s Lake Albert oil fields to Africa’s east coast in Tanzania, has already displaced thousands of people and cuts through the Lake Victoria basin, one of East Africa’s major freshwater systems and a critical water source for around 40 million people.

    According to the BankTrack non-profit, when the pipeline is at peak production, it will carry 216,000 barrels of crude oil per day and release over 33 million tonnes of carbon emissions each year. Over its full lifetime of 25 years, it is estimated to release about 379 million tonnes of greenhouse gas emissions across its value chain including construction, refining and product use.

    A May 2026 report from Earth Insight also warns that the pipeline and related infrastructure could affect 158 wetlands in Uganda, 11 rivers, 44 protected areas and seven key biodiversity areas while disrupting about 2,000 square km of protected wildlife habitats.

    This is why the primary focus of the UK court case is to stop the operation of the pipeline in its tracks, Leigh Day’s Willers said, calling it a “carbon bomb” that would worsen the world’s climate crisis.

    Long wait for first hearing

    While the purpose of the case is to stop the pipeline from launching operations, Renshaw said it could take about 12 months before the case gets a first hearing and about 18 months before it goes to trial.

    Billions unlocked as Green Climate Fund agrees to spend more and save less

    The farmers are, however, seeking an injunction to stop EACOP Ltd from proceeding with operations. In the event that shipments begin, the lawsuit will still seek to stop the pipeline from then on, Renshaw said.

    “We will be doing what we can to expedite matters but it is possible that EACOP will have started operating the pipeline before the claim is heard. If that is the case, the claim would intend to halt operations from that point. For example, the pipeline may operate for just one year rather than 30-plus, resulting in far less harm,” he said.

    The post Ugandan farmers launch UK court case against East African oil pipeline appeared first on Climate Home News.

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    Cited 7 July 2026: ‘Impossible’ heat | Global ocean record | Climate change and the ozone hole

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    Welcome to Cited, your essential guide to new climate research.

    In the news

    ‘HEAT ALERT’: At least 25 people died as a “heat dome” smothered the eastern half of the US, reported the Guardian, with more than 20 states under “stifling temperatures more than 100F (38C)”. More than 140 million people were under heat alerts, the outlet said, with dead bodies found in “homes with no air conditioning, outside their residences, on the street and in parked cars”. Analysis by World Weather Attribution (WWA) found that the combined heat and humidity would have been “virtually impossible” without human-caused warming, reported the New York Times.

    ‘MORTALITY WILL RISE FURTHER’: Meanwhile, extreme heat continued to hit Europe, with Le Monde reporting on temperatures of 40C in France, Portugal and Spain again this past weekend, alongside “devastating” wildfires. Public Health France doubled its preliminary estimate of the “excess deaths” from the extreme heat in late June, from 1,000 to more than 2,000, according to the Guardian. The higher figure was still “probably an underestimate”, the agency said. Analysis published by Carbon Brief put the figure at 2,700 heat-related deaths. A WWA attribution study, covered by Carbon Brief, found that Europe’s June heatwave would have been “virtually impossible” even 50 years ago.

    ‘BOOST TO GLOBAL TEMPERATURES’: The UN World Meteorological Organization (WMO) “raised its forecast for ​the rapid emergence of a strong El Niño in the coming months, ‌warning that the phenomenon is likely to drive global temperatures higher”, reported Reuters. A WMO scientist told the newswire that “El Niño conditions have emerged ⁠in the equatorial Pacific and there is a remarkable agreement between forecast models that ​this will be a strong El Niño”.

    Research picks

    Extremes

    • The annual season when “intense” tropical cyclones occur has lengthened by 10-14 days per decade across the world since the 1980s | Nature Communications
    • There is an “increasing” and “overlooked” global threat from glacial outburst floods from small lakes | Nature Sustainability
    • Female smallholder farmers in sub-Saharan Africa experience crops losses 2-2.5 times greater than male smallholders in periods of extreme heat | Nature Sustainability

    Policy

    • The summaries for policymakers in Intergovernmental Panel on Climate Change (IPCC) mitigation reports over 2001-22 “have not yet become more solution-oriented while abiding by their policy-neutrality principle” | npj Climate Action
    • Two-thirds of countries address inequality in their national pledges under the Paris Agreement – particularly in “countries with lower levels of human development and greater income inequality” | Climate and Development
    • To “future proof” the Paris Agreement’s “well-below 2C” limit, it should be interpreted as a median “peak warming” of 1.6-1.8C, rather than a 66-90% chance of staying below 2C | Nature Climate Change

    Land sink

    • From 2001 to 2015, northern Eurasia absorbed about 0.47bn tonnes of carbon each year – around one-third of the total global land carbon sink | Global Biogeochemical Cycles
    • Model simulations of potential land-use carbon emissions out to 2100 show that “deforestation and forest regrowth dominate variability” of emissions, with policy timing and ambition “exerting strong control” | Nature Communications
    • Tropical forests are facing an increase in areas that exceed critical temperatures where their “photosynthetic system breaks down” | Proceedings of the National Academy of Sciences

    Captured

    On 21 June, global average sea surface temperature (SST) reached a record high for the day of the year, according to the Copernicus Climate Change Service (C3S). Daily SST for the global ocean, excluding polar regions, reached 20.86C on 21 June, exceeding the 20.83C reached on the same day in both 2023 and 2024, the C3S said. Global SST has remained at record levels for every day since. The conditions “could indicate the beginning of a new phase, leading, once more, to uncharted territory”, said C3S director Carlo Buontempo.


    56 hours and 30 hours

    The amount of time that the average lifespan of tropical cyclones in the north-east and north-west Pacific has shortened, respectively, over 1982-2024, according to a study in npj Climate and Atmospheric Science. This shorter lifespan “compresses the time available for weather forecasting and disaster preparedness”, the authors said.


    Spotlight

    The ozone hole and climate change

    As a new “thought experiment” asks whether the hole in the ozone layer could, theoretically, have been identified decades before it was discovered, Carbon Brief explores the interactions between climate change and the ozone hole.

    It is now more than 40 years since the discovery of the hole in the ozone layer over Antarctica, detailed in the journal Nature in 1985.

    A study more than a decade earlier had predicted that chlorine-based substances – such as chlorofluorocarbons (CFCs) – could lead to the destruction of ozone in the stratosphere.

    So, in theory, how early could the ozone hole have been detected?

    New research, published in the Proceedings of the National Academy of Sciences, explored this very question.

    Study co-author Prof Susan Solomon from the Massachusetts Institute of Technology is a leading atmospheric scientist. In the late 1980s, Solomon and colleagues identified the mechanism behind how CFCs were causing ozone depletion.

    The new study is a “thought experiment”, Solomon told Carbon Brief, asking when scientists could have discovered the ozone hole had they had access to modern satellite observations.

    “We found that depletion could have been detected as early as 1957 in the tropical upper stratosphere, where natural variability is especially small,” explained Solomon.

    This would have been before the use of CFCs became widespread, Solomon added. Instead, early ozone depletion was caused by carbon tetrachloride, a chemical used as a cleaning agent, as well as in fire extinguishers and for producing refrigerants.

    For many decades, the ozone hole and global warming have often been confused by the public and the media, Solomon explained:

    “It’s common to imagine that because ozone is so important at shielding us from the UV [ultraviolet] light that causes skin cancer, then having less ozone must mean the Earth would warm up.”

    For example, in a 1995 editorial, the Los Angeles Times congratulated the Nobel prize-winning chemists who identified the threat of CFCs to the ozone layer. The newspaper noted that these processes “threaten calamitous global warming by damaging the Earth’s protective layer of ozone”.

    However, said Solomon, “the Earth is warmed much more by visible light – UV doesn’t really contribute, so ozone depletion doesn’t cause significant warming”.

    Regional impacts

    The depletion of ozone actually has a very small cooling effect at the Earth’s surface. But this is more than outweighed by the warming impact of CFCs and other ozone-depleting substances.

    This warming impact means that efforts to reverse ozone depletion have had a beneficial impact on the climate.

    The Montreal Protocol, a 1987 international agreement to phase out CFCs, “has played – and is playing – a very substantial role in safeguarding climate too”, said Solomon:

    “It turns out that the CFCs and their replacement gases HCFCs [hydrochlorofluorocarbons] are strong greenhouse gases, so phasing out their production has not only avoided a lot of ozone depletion that would otherwise have occurred, it also had a big influence on global warming.”

    HCFCs were considered as “transitional substitutes” for CFCs – they still damaged ozone, but to a lesser extent – until ozone-safe alternatives were commercially available.

    Hydrofluorocarbons (HFCs), which are not ozone depleting, began to be used widely in the 1990s. However, HFCs are also potent greenhouse gases. HFCs and similar replacements are now being phased out under the 2016 Kigali Amendment to the Montreal Protocol.

    While the ozone hole itself has only a very small impact on global temperatures, it does have a clear impact on the regional climate over Antarctica.

    Prof David Thompson from Colorado State University, working with colleagues including Solomon, has published research demonstrating that “changes in southern-hemisphere winds linked to the stratospheric ozone losses extend all the way down to the ground in some seasons”, explained Solomon.

    This has “reduc[ed] warming that would have occurred in interior Antarctica and enhanc[ed] warming in the Antarctic Peninsula region”, she said.

    The knock-on impacts include “wind changes [that] actually extend beyond Antarctica to the mid-latitudes of the southern hemisphere, where they even affect rainfall”, she added.

    Preprints to watch

    Carbon Brief’s pick of new papers under review

    • The drying impact over Africa from using stratospheric aerosol injections to stabilise global temperatures would only be minimised “when combined with a strong decarbonisation effort” | Earth System Dynamics
    • The El Niño-Southern Oscillation and Indian Ocean Dipole could “shape” the playing conditions at the Rugby World Cup 2027 in Australia | Journal of Southern Hemisphere Earth Systems Science
    • A “strong” weakening of the Atlantic Meridional Overturning Circulation (AMOC) would “profoundly alter the climate-carbon cycle system”, underscoring the “importance of explicitly accounting for AMOC risks in long-term climate assessments” | Earth System Dynamics

    Noticeboard

    • 6 July-25 September: Registration open for experts to review the first-order draft of the Intergovernmental Panel on Climate Change’s Working Group I report 
    • 7-15 July: UN High-level Political Forum on Sustainable Development, New York
    • 19 July: Application deadline for a postdoctoral scholar in transdisciplinary climate research at Penn State University, US | Salary: unknown
    • 22 July: Application deadline for PhD project on “climate change impacts on the Antarctic coastal ocean carbon sink” at the University of East Anglia, UK
    • 26 July: Application deadline for PhD projects on “AI for land-atmosphere feedbacks during hydroclimatic extremes” at the Helmholtz School for Integrated Data Science in Environmental & Life Sciences, Germany
    • 29 July: Application deadline for an assistant professor in Earth and environmental geosciences (palaeoclimatology) at Colgate University, US | Salary: $97,500-101,500
    • 31 July: Application deadline for PhD project on Arctic Ocean methane oxidation at Stockholm University, Sweden

    Cited is researched and written by Cecilia Keating, Robert McSweeney, Ayesha Tandon, Daisy Dunne and Dr Giuliana Viglione.

    Please send tips, feedback and upcoming climate research to cited@carbonbrief.org

    This is an online version of Carbon Brief’s fortnightly Cited email newsletter. Subscribe for free here.

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

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    In June 2026, a record-breaking heatwave swept across Europe, with France among the first and hardest hit countries.

    In a new analysis, we estimate that the extreme conditions caused more than 2,700 heat-related deaths in France.

    We also show how France’s extreme temperatures in June exceeded projections from climate models.

    Our findings illustrate the human toll of extreme weather as the world warms.

    We also highlight the challenges in projecting the magnitude of future heatwaves and their impacts on people.

    Outpacing projections

    For most of this century, Europe has seen summer heat extremes that outpace projections from climate models.

    Several different factors likely explain this trend, including reductions in planet-cooling aerosols as nations have cleaned up their air pollution, as well as changes in atmospheric circulation patterns, which models struggle to represent.

    In June 2026, daily high temperatures averaged across France reached 36.9C, shattering the previous June record set in 2022 by 2.4C.

    [For more on the impacts and coverage of Europe’s June heatwave, see Carbon Brief’s explainer.]

    The rise in observed temperatures in France has outpaced projections made by climate models, with June maximum temperatures more in line with what was expected for the 2070s.

    This is illustrated in the figure below, which shows how France’s average maximum daily high temperature for June recorded in 2026 (black line) compares to climate model projections (blue and orange lines).

    Comparison of observed (ERA5, black) and modelled (blue and orange) temperatures across France from 2000 to 2080. Plot shows the maximum daily high temperature recorded in June for each year, after averaging temperatures across France. The model ensembles are bias-corrected CMIP6 model ensembles from the NEX-GDDP (blue) and CIL-GDPCIR (orange) projects. The dashed blue and orange lines are the ensemble averages. Credit: Prof Andrew Dessler.
    Comparison of observed (ERA5, black) and modelled (blue and orange) temperatures across France from 2000 to 2080. Plot shows the maximum daily high temperature recorded in June for each year, after averaging temperatures across France. The model ensembles are bias-corrected CMIP6 model ensembles from the NEX-GDDP (blue) and CIL-GDPCIR (orange) projects. The dashed blue and orange lines are the ensemble averages. Credit: Prof Andrew Dessler.

    Counting the death toll of climate change

    The downstream impacts of these extreme temperatures are lethal.

    Scientists are able to estimate the death toll of high temperatures in many locations, depending on the availability of mortality and climate data.

    There are several ways to do this.

    One option is to examine death certificates to see which deaths have been directly recorded by physicians as related to heat. However, there is strong evidence that this method significantly undercounts heat-related deaths, as most death certificates do not consider environmental factors such as heat when diagnosing the cause of death.

    Alternatively, it is possible to calculate the rate of total (“all-cause”) mortality in a given time period relative to previous time periods – for example, by comparing the total number of deaths in June 2026 compared to the average of previous Junes. This “excess deaths” figure can be used as an estimate of the deaths from a heat wave.

    Using this approach, Public Health France attributed around 2,000 deaths in France to the extreme heat in the week of 22-28 June.

    Finally, scientists can use long-term data on overall mortality and correlate changes in mortality with changes in temperature to understand the statistical relationship between the two.

    Research published in Proceedings of the National Academy of Sciences in 2025 that used this third approach found that mortality rates in France increase rapidly in cold or hot conditions as daily maximum temperatures depart further from approximately 20C.

    This pattern of a U-shaped response of mortality to temperature – shown in the figure below – is very consistent across time periods and regions around the world.

    Chart showing the relationship between extreme heat and mortality in France
    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)

    To calculate the death toll of the June 2026 heatwave in France, we compared observed temperatures over 12-29 June to their baseline average over 1980-2025.

    The difference between these two temperatures helps us understand how many more people died than they would have in the absence of such extreme conditions.

    Over 12-29 June, we found that France has experienced around 2,700 heat-related deaths above the average baseline. Day-to-day heat-related mortality rates rose from less than 100 to almost 300 on the hottest days of 24 and 25 June.

    This is shown in the graph below, which illustrates the cumulative total heat-related deaths seen in France over the two-and-a-half week period. The inset shows how heat-related deaths fluctuated on a day-to-day basis during this time.

    Chart showing the number of deaths from heat in France during the June 2026 heatwave
    Estimated heat-related mortality over 12-29 June, based on a U-shaped response of mortality to temperature. The main plot shows cumulative total deaths and the inset shows daily deaths. Credit: Dr Christopher Callahan, based on data and methods in Callahan et al. (2025)

    Recent analysis by World Weather Attribution has already shown that human-caused climate change increased the frequency and intensity of the June heat wave across Europe.

    Meanwhile, previous research has shown there is substantial evidence that heat-related mortality in Europe has already been elevated by greenhouse gas emissions.

    As a result, we can be confident that at least some of the more than 2,700 deaths already seen in France are directly due to the burning of fossil fuels.

    Calculating climate risk

    In April, the UN-led body responsible for coordinating the work of climate modelling centres – the Coupled Modelling Intercomparison Project (CMIP) – unveiled a set of seven new emissions scenarios.

    These are designed to replace the previous scenarios that have been used by scientists to understand how the climate might change in the future. They will feed into the upcoming seven assessment report (AR7) of the Intergovernmental Panel on Climate Change (IPCC).

    The range of future emissions in the new CMIP scenarios is smaller, with scenarios of very high or very low emissions no longer on the table.

    The retirement of the very-high emissions scenario – known as “RCP8.5” – led to certain commentators in the media and in politics, including US president Donald Trump, arguing that the risks of climate change had been “overstated”.

    [For more on false and misleading claims around the new emissions scenarios, see Carbon Brief’s factcheck.]

    Our analysis of June’s heat-related deaths in France suggests that, even if the most severe emissions pathways are no longer needed, climate impacts are taking a heavy toll on society.

    Moreover, the temperatures seen in France show that climate models continue to underpredict the magnitude of heatwaves for a particular level of global warming.

    This is because greenhouse gas emissions are only a first step in estimating the impacts of climate change.

    The second step is converting emissions to changes in the climate at both the global and local levels – or hazards. This includes heatwaves, flash floods and droughts.

    The third step is to determine how changes in the hazards will affect local populations. This can be determined by calculating people’s exposure and vulnerability to hazards.

    Substantial uncertainty persists at every stage of this sequence.

    For example, scientists do not know exactly how the global climate will react to ever-rising greenhouse gas emissions – nor the extent to which global temperature increases will drive local climate hazards. We also do not know how climate change at a local level impacts human health outcomes.

    Managing the future of heat risk

    Almost all heat-related deaths are preventable.

    Adaptation options, such as air conditioning, heat action plans and social support for isolated people, will be crucial as the climate moves away from the typical conditions that people are used to.

    Our previous research showed that France made a lot of progress reducing heat-related mortality after the deadly 2003 summer heatwave by taking many of these actions.

    Adaptation can reduce deaths, but it cannot eliminate the risk created by continued warming.

    Without a move away from fossil fuels, future heatwaves will keep testing the limits of public health systems and more people will die.

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