Lancet Countdown 2026 Report: Heat Deaths Hit Record 710,000 as Authors Call Climate Change a Global Health Emergency
The Lancet Countdown 2026 report on health and climate change, published in The Lancet on Oct. 28, 2026, concludes that the health harms of a warming planet are growing faster than the world’s response. Its headline estimate: heat was linked to a record 710,000 deaths worldwide in 2023, and more than 70% of those deaths are attributed to human-caused climate change. The authors, joined by the World Health Organization, are calling for climate change to be treated as a global health emergency.
This is the 10th annual Lancet Countdown assessment. It arrives less than two weeks before the COP31 climate talks open in Antalya, Türkiye, on Nov. 9. Below is a plain-language breakdown of what the report found, how the numbers were produced, who is most affected, and where the evidence has limits.
Key Takeaways
- Record heat deaths: An estimated 710,000 heat-related deaths in 2023, the hottest year in the study period, with 71.5% attributed to climate change.
- A rising share caused by warming: Heat was linked to an average of about 540,800 deaths a year in 2016–2023. The share attributed to climate change rose to 68%, up from 55% in 2006–2015.
- Economic toll: Lost work capacity from heat cost an estimated US$1.07 trillion in 2025, the third straight year above $1 trillion.
- Clean energy is growing: Global clean energy investment hit a record US$2.1 trillion in 2025, and cleaner air is estimated to prevent about 323,000 deaths a year in countries where fossil-fuel pollution has fallen.
- But fossil fuels still dominate: They supply more than 80% of global energy, and fossil-fuel air pollution is estimated to kill 2.73 million people a year.
What Is the Lancet Countdown 2026 Report?
The Lancet Countdown on health and climate change is an international research collaboration led by University College London (UCL) and developed with WHO as a strategic collaborator. The 2026 edition was produced by 146 researchers across more than 30 countries. (The Lancet Countdown website lists 71 collaborating institutions; WHO’s announcement describes “more than 100 institutions.”)
The report is formally titled “The 2026 report of the Lancet Countdown on health and climate change: a decade of escalating health harms and a decisive moment for all,” with Marina Romanello as lead author. It tracks 54 indicators, four of them new this year, covering health hazards, adaptation, emissions cuts, finance, and public and political engagement.
Lancet Countdown 2026 Report Findings: Verified Figures
The figures below are the report’s own modeled estimates, as published by the Lancet Countdown and summarized by WHO and News-Medical.
Heat and mortality
| Measure | Estimate |
|---|---|
| Heat-related deaths, 2023 (record year) | ~710,000 (71.5% attributed to climate change) |
| Average heat-related deaths per year, 2016–2023 | ~540,800 |
| Share attributed to climate change, 2016–2023 | 68% (~369,900 a year) |
| Share attributed to climate change, 2006–2015 | 55% (~219,100 a year) |
| Change in average annual heat deaths vs. prior decade | Up nearly 36% |
| Heat deaths attributed to climate change, 2016–2023 total | Almost 3 million |
This is the first time the Countdown has directly quantified the share of heat deaths attributable to human-caused climate change, according to report co-authors quoted by ABC News (Australia).
Work, income and the economy
- Heat-reduced work capacity cost an estimated US$1.07 trillion in 2025, about 0.91% of global economic output.
- Losses as a share of GDP were heaviest in South-East Asia (3.9%) and Africa (3.2%), compared with 1.5% in the Americas and 0.2% in Europe.
- Agriculture (38%) and construction (29%) absorbed the largest shares of losses.
Drought, water and extreme rain
- 51.8% of global land saw at least one month of extreme drought in 2025, the second-worst year on record after 2023.
- Very extreme rainfall affected about 17.2% of global land each year in 2016–2025, up from 14.8% the decade before.
- A new satellite indicator finds 43% of land has had a long-term decline in water storage since 2003, and 37% a long-term rise.
Signs of progress
- Clean energy investment rose 7.2% in 2025 to a record US$2.1 trillion, 82% more than the roughly US$1.16 trillion invested in fossil fuels.
- Renewables rose from 5.5% of electricity generation in 2016 to 13.5% in 2023.
- 56 of 194 WHO member states now have a national health adaptation plan, up from 14 in 2015.
- Funding for climate-related health research rose from US$42 million in 2016 to US$316 million in 2024, though 84% goes to researchers in the wealthiest countries.
Fossil fuel trends
- The 100 largest oil and gas companies plan production that would be 150% above levels compatible with 1.5°C by 2040, up from 138% in last year’s report.
- Net fossil fuel subsidies reached record levels in 2022–2024 and total about US$6.2 trillion since the Paris Agreement. Ten countries spent more on these subsidies in 2024 than on their health systems.
How the Research Was Done
The Countdown is an indicator report, not a single clinical trial or experiment. Its teams combine climate data, health records, economic statistics, satellite observations, and country surveys into 54 tracked indicators.
- Heat-death attribution: Heat mortality is estimated with excess-mortality models. To attribute deaths to climate change, researchers compare modeled temperatures with and without human greenhouse-gas emissions, an approach known as fraction attributable risk.
- Health system indicators: These rely largely on WHO member-state reporting and surveys.
- Adaptation finance: Estimates of needs draw on the 48 of 79 developing countries that have completed costing assessments.
Who Is Affected
The report finds the burden falls hardest on people and countries least responsible for emissions. Low- and middle-income countries carry the largest heat-related income losses, with agriculture accounting for 71% of such losses in Africa. Outdoor workers, older adults, and communities without cooling or reliable water are among the most exposed. The authors also warn that the current El Niño could compound climate impacts and trigger humanitarian crises; WHO says it has run a graded emergency response to El Niño health impacts since September.
What the Experts Are Saying
The following are statements and commentary, not independently verified findings.
- Prof. Marina Romanello, executive director of the Lancet Countdown at UCL, said the findings show “the health harms of climate change are growing faster than the world’s response to them.”
- Dr. Diarmid Campbell-Lendrum, who heads WHO’s climate change and health unit, said the report “demonstrates that climate action is a health intervention.”
- Helen Clark, chair of the Lancet Countdown board and former prime minister of New Zealand, said: “What’s missing is not evidence, but the political will to act on it.”
Limitations and Caveats
- Modeled estimates: Death and income figures are estimates, not counts of death certificates. Heat is rarely listed as a cause of death, so models are used to infer its role. Results depend on model assumptions and data quality, which vary by region.
- Self-reported data: Several health-system indicators rely on what countries report to WHO, not independent verification.
- Incomplete coverage: Adaptation cost estimates cover only 48 of 79 developing countries, and research funding is concentrated in wealthy nations, leaving evidence gaps where risks may be greatest.
- Advocacy framing: The report pairs data with policy recommendations, such as declaring a global health emergency and phasing down fossil fuels. Readers should separate the measured indicators from the authors’ recommendations.
What Happens Next
COP31 runs Nov. 9–20, 2026, in Antalya, Türkiye, where WHO will host a Health Pavilion. The Countdown authors want health placed at the center of negotiations on emissions, adaptation finance, and fossil-fuel subsidies. Regional Countdown reports, including one covering Oceania, are expected to follow.
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Sources
- The Lancet: The 2026 report of the Lancet Countdown on health and climate change (DOI: 10.1016/S0140-6736(26)01779-4)
- Lancet Countdown: 2026 Report
- WHO: Climate change is a growing health emergency, Lancet Countdown warns (Oct. 28, 2026)
- News-Medical: Climate change intensifies global health risks, Lancet Countdown report warns
- ABC News (Australia): Global Lancet study counts almost 3 million climate change-related deaths
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