Global heat mortality data

According to the Lancet Countdown for Health and Climate Change, heat-related deaths have risen by 63 percent since the 1990s, [1] reaching an estimated 546,000 deaths per year between 2012 and 2021 – the equivalent of one person every minute of every year. [2] In 2024, the hottest year on record, the average person was exposed to 16 health-threatening hot days directly attributable to climate change. Other authoritative measures of global heat mortality from the Global Burden of Disease Study (GBD) [3] and the Multi-Country Multi-City Collaborative Research Network (Zhao et al.) use different tracking methods but arrive at a similar scale of impact (see Table 1)

TABLE 1: Summary of Key Global Heat Mortality Studies

	Lancet Countdown 2025 report (2012–2021 avg)	Global Burden of Disease (GBD) Study (2023)	Zhao et al. Lancet Planetary Health 2021 (2000–2019 avg)[4]
Global heat-mortality figure	546,000 heat-related deaths per year	539,246 deaths attributed to high temperature risk	490,000 heat-attributable deaths per year
Explanation of estimate	The Lancet Countdown tracks heat-related mortality using epidemiological models linking daily gridded temperature, humidity, and cause-specific mortality data. Its methodology calculates excess deaths by comparing current temperatures to an "optimal" temperature threshold, utilizing data from the GBD study for base mortality rates.	Using 64.9 million individual death records from nine countries (Brazil, Chile, China, Colombia, Guatemala, Mexico, New Zealand, South Africa, and the USA) the GBD estimated how much heat increases the risk of dying from 17 specific causes, then applied those risk relationships to modelled death counts across 204 countries worldwide.	Using death records and weather data from 750 locations across 43 countries, Zhao et al. calculated how total deaths, from all causes combined, rise and fall with temperature, then extrapolated that relationship across a global grid to estimate the worldwide toll.
Country-level data	No published country ranking. Regional analysis notes the largest increases in heatwave exposure in Africa, Asia, and Small Island Developing States.	Yes - 204 countries. The countries with the highest modelled heat mortality are in South Asia, Sub-Saharan Africa, and North Africa.	Yes - 0.5° grid resolution with the study noting that most grids with a high density of excess deaths were in large, low-lying, crowded coastal cities in Eastern and Southern Asia and cities in Eastern and Western Europe.

These figures are alarming. They are also, almost certainly, underestimated, because the regions carrying the greatest heat burden are often those with the weakest systems for counting heat deaths. The epidemiological tools that generate these global estimates were built overwhelmingly on data from the Americas, Europe, and East Asia. Africa, is home to over 1.4 billion people, is warming at approximately 1.5 times the global rate, and is projected to face some of the most severe heat mortality increases this century.[5][6] However, Africa contributed just three of 237 studies in the most comprehensive recent global scoping review of heat-health research methods, barely 1 percent of the literature (Graffy et al.,2024). None of those three studies (from Ghana, Niger and Senegal) focused on heat mortality specifically. And where direct evidence from Africa does exist, it is striking: a 2025 study drawing on Health and Demographic Surveillance System data from 11 sites across eight Sub-Saharan African countries found that heat vulnerability is not decreasing (as it has in high-income regions) but increasing, with nighttime heatwave mortality risk rising significantly between 2005 and 2010 and, 2011 and 2015 (He et al., 2025). The absence of data indicates a significant measurement gap, and the limited evidence that does exist suggests the true burden may be far greater than global estimates currently suggest.

Looking ahead, the Climate Impact Lab projects that countries across the Sahel, such as Burkina Faso and Niger, could see temperature-related mortality increases exceeding 60 deaths per 100,000 people by 2050,[7] which is greater than the current mortality rate from malaria, while 10 times more people in lower-income countries are projected to die from extreme temperatures than in higher-income countries, despite roughly equal populations. Importantly, this study highlights that investments in contextual adaptation measures,taking many forms such as changes in behaviour or adoption of cooling technologies, will be critical in low-income countries. This is explored more in Cooling access & heat mortality.

The interactive map below shows current heat mortality rates based on data from the GBD study.[8] The subsequent bar chart compares the 12 countries that appear in the top 20 countries for current heat mortality and Climate Impact Lab’s data on projected change in heat mortality to 2050. These countries are facing severe heat mortality today and anticipate the steepest projected increases in the decades ahead, due to the combined trends of warming and growing and aging populations. Overwhelmingly concentrated in Sub-Saharan Africa and the Middle East and North Africa, they are: Bahrain, Burkina Faso, Chad, Djibouti, Iraq, Kuwait, Mali, Mauritania, Niger, Pakistan, Saudi Arabia, and Sudan.

FIGURE 1: Estimated deaths attributable to heat exposure in 2023, by country. Colour reflects total (male + female) deaths on a logarithmic scale. Select any country for a breakdown.

Heat-Related Mortality, 2023

Estimated deaths attributable to heat exposure by country, from the Global Burden of Disease study.

Total heat-attributable deaths (2023)

0101001k10k100k+

No data available

Source: Data reproduced by SEforALL, based on Global Burden of Disease Collaborative Network. Global Burden of Disease Study 2021 (GBD 2021).Available at: vizhub.healthdata.org/gbd-results [Query parameters: measure: deaths; risk factor: high temperature; cause: all causes; age: all ages; sex: both; year: 2023. Accessed July 2025.])

FIGURE 2: Countries that fall in the top 20 by both current heat deaths and projected additional heat mortality in 2050 (deaths per 100,000 people).

Source: Global Burden of Disease Study (2023); Climate Impact Lab’s moderate RCP4.5 emissions scenario (2040-2059)

This dual risk of a high burden now and a worsening burden ahead means that action is urgently needed. These are not countries where adaptation can wait, nor where today's response alone will suffice. They require investment that addresses the present crisis while building the long-term resilience, surveillance, and cooling infrastructure that is needed for a hotter future

How heat kills & who is at risk

Measuring heat-related mortality

Cooling access and heat mortality

Passive and nature-based cooling

Low-energy and mechanical solutions

Heat resilience, cooling access and mortality

Notes and references

[1] Estimates are not age-adjusted, which means that these estimates include impacts from older populations alongside changes in climate.
[2] Romanello M, Walawender M, Hsu S-C, et al. The 2025 report of the Lancet Countdown on health and climate change: climate change action offers a lifeline. The Lancet. 2025. DOI: 10.1016/S0140-6736(25)01919-1
[3] Global Burden of Disease Collaborative Network. Global Burden of Disease Study 2021 (GBD 2021) Results. Seattle: Institute for Health Metrics and Evaluation (IHME); 2024. Available at: https://vizhub.healthdata.org/gbd-results [Query parameters: measure: deaths; risk factor: high temperature; cause: all causes; age: all ages; sex: both; year: 2023. Accessed July 2025.]
[4] Zhao Q, Guo Y, Ye T, Gasparrini A, Tong S, Overcenco A, et al. Global, regional, and national burden of mortality associated with non-optimal ambient temperatures from 2000 to 2019: a three-stage modelling study. Lancet Planetary Health. 2021;5(7):e415–e425. DOI: 10.1016/S2542-5196(21)00081-4
[5] United Nations Department of Economic and Social Affairs, Population Division. World Population Prospects 2024. Available at: https://population.un.org/wpp
[6] He C, Zhu Y, Guo Y, Bachwenkizi J, Chen R, Kan H, Fawzi WW. Escalated heatwave mortality risk in sub-Saharan Africa under recent warming trend. Science Advances. 2025;11(48). DOI: 10.1126/sciadv.ady7379
[7] Grover-Kopec E., Carleton T., & Greenstone M. (2026, March 25). Human health: Measuring the impact of rising temperatures on mortality to target adaptation planning. Climate Impact Lab. https://impactlab.org/research/human-health-measuring-the-impact-of-rising-temperatures-on-mortality-to-target-adaptation-planning
[8] Global Burden of Disease Collaborative Network. Global Burden of Disease Study 2021 (GBD 2021) Results. Seattle: Institute for Health Metrics and Evaluation (IHME); 2024. Available at: https://vizhub.healthdata.org/gbd-results [Query parameters: measure: deaths; risk factor: high temperature; cause: all causes; age: all ages; sex: both; year: 2023. Accessed July 2025.]