Developing Countries Will Feel the Heat of Climate Mortality

Climate mortality is more complex, and globally unequal, than many assume

What is the most cited cause of climate concern? In the UK, it is not the impact of flooding, access to food or water supply shortages. Instead, according to the Office for National Statistics (ONS), the direct effects of rising temperatures are the leading cause of climate concern in the UK.¹

Are these concerns warranted? How are people in the UK likely to be affected by rising temperatures? This article will focus on the direct effects of rising temperature on mortality. To do this we will start in England, before moving to Europe and finally taking a global perspective.

I find stark a geographic inequality in the impacts of rising temperatures on mortality. In Europe, and developed countries more broadly, there is evidence to suggest decreases in cold deaths may offset increases in heat deaths. For some developing countries, substantial negative effects are projected.

Historic Climate Mortality in England

The ONS Climate Related Mortality publication illustrates that England has historically had both a cold weather problem and, to a lesser extent, a hot weather problem. Between 1998 and 2022, for every heat related death there were four cold related deaths.²

As part of this publication, the ONS conducts analysis to show the direct relationship between temperature change and mortality. Other factors affecting mortality such as seasonality, the day of the week or air pollution are controlled for, isolating the direct impact of temperature on mortality.

This analysis shows that cold related deaths are associated with seemingly mild temperatures. For those aged 65 and older, cold related deaths occur at temperatures as high as 15°C. For under 65s, cold related deaths occur at temperatures of 12°C and lower.

The persistence of cold related deaths at seemingly mild temperatures explains why cold temperatures have, up until now, been the principal driver of climate mortality in England.

Future Climate Mortality in Europe

As the climate warms, the balance of cold and heat related deaths will change in England and elsewhere in the world. In certain regions, a decrease in cold related deaths will be insufficient to offset an increase in heat related deaths, whilst, in other regions, global warming will reduce climate mortality. In Europe, it is unclear in which direction the scales will tip.

A study by a team of researchers from the London School of Hygiene & Tropical Medicine, found that a scenario of warming that broadly aligns with the warming expected from current policy commitments (SSP2-4.5) would have no statistically significant impact on aggregate mortality in Europe.³

This finding was in the absence of any climate adaptation. Climate adaptation is the human response to reduce the risks associated with climate change.⁴ As such, climate adaptation would be expected to reduce heat-related mortality, increasing the likelihood that remaining heat deaths are more than offset by reductions in cold deaths.

Only in a scenario that implies 4°C of warming (SSP3-7.0), did this study find a statistically significant change in European climate mortality. This is considerably more warming than the 2.6°C of warming that current climate policies are expected to deliver. In this pessimistic scenario, statistically significant increases in mortality are only found in southern Europe and Bulgaria. Across all other countries in Northern, Eastern and Western Europe (including the UK) the direct effects of rising temperatures are found to have no statistically significant impact on climate mortality.⁵

Future Global Climate Mortality

In 2022, a team of researchers from the Climate Impact Lab at the National Bureau of Economic Research (NBER) sought to quantify the global damages associated with climate mortality.⁶ This study was innovative in considering both the costs and benefits of adaptation to changing temperatures.

This study found a polynomial relationship between temperature increases and mortality, meaning that once temperatures exceed 30°C, small increases in temperature have much increased impacts on mortality.⁷ Therefore, increases in climate mortality will be concentrated in already hot countries, where average temperatures are already closer to this inflection point.

Developing countries are disproportionately represented in this group of ‘already hot countries’. This inequality in impact will be amplified by the limited resources that developing countries have to invest in adapting to higher temperatures.

Climate adaptation in developed countries will mean aggregate climate mortality will fall; warmer temperatures will lead to fewer cold deaths, and a large share of heat deaths will be avoided through adaptation.⁸ In contrast, this study found that little adaptation will occur in developing countries, resulting in large increases in climate mortality.

In line with the research discussed above, this NBER study finds no evidence to suggest that rising temperatures will have a direct positive effect on aggregate climate mortality in Europe. This finding is consistent across both a RCP8.5 emissions scenario⁹ – an emissions scenario that the IPCC consider as having become “considerably less likely” over recent years¹⁰ – and an RCP4.5 emissions scenario – an emissions scenario¹¹ that more closely aligns with current climate policies.¹² This finding is also consistent regardless of whether adaptation to rising temperatures is considered.

In contrast to this bullish outlook for Europe, current trajectories of climate change will increase climate mortality in developing countries, imposing a large social and economic burden. The NBER study estimates that the direct effects of increased climate mortality will substantially decrease the economic output of some countries: output in Pakistan and Bangladesh is estimated to decrease by 8% and 4.5% respectively.

Rising temperatures will have impacts beyond mortality. For example, a 2012 study by Dell, Jones and Olken found evidence that higher temperatures may reduce rates of economic growth. Less direct effects, such as other extreme weather events, will also lead to economic and social impacts beyond those covered in this article. Whilst some countries may ‘gain’ from reduced climate mortality, this does not mean these same countries will benefit from climate change more broadly.

To Summarise

Here is what you should take away from this article:

1. Increased climate mortality will have the most impact in developing countries, where temperatures tend to already be higher and less climate adaptation is expected to occur.

2. The aggregate effects of climate change on mortality in both Europe, and developed countries more broadly, are uncertain. In Europe, there is evidence to suggest that, with adaptation, decreases in cold deaths may actually offset increases in heat deaths.

3. The direct effect of rising temperatures on climate mortality is only one of many mechanisms by which climate change will impact lives in developed countries.

1. ONS’s Worries About Climate Change Publication.

2. Climate-related mortality, England and Wales: 1988 to 2022. There were an estimated 199,298 cold-related deaths, compared to an estimated 51,670 heat-related deaths.

3. Masselot, P., Mistry, M.N., Rao, S. et al. (2025), Estimating future heat-related and cold-related mortality under climate change, demographic and adaptation scenarios in 854 European cities. Nat Med 31, 1294–1302. Pg. 1295.

4. In the context of adapting to mitigate climate mortality, research has found that the most successful adaptation in the USA has been the expansion of air-conditioning, which was responsible for “virtually the entire decline in the temperature-mortality relationship” in the 2nd half of the 20th century. Source: Alan Barreca, Karen Clay, Olivier Deschenes, Michael Greenstone, and Joseph S. Shapiro, (2013), "Adapting to Climate Change: The Remarkable Decline in the U.S. Temperature-Mortality Relationship over the 20th Century," NBER Working Paper 18692.

5. Masselot, P., Mistry, M.N., Rao, S. et al. (2025), Estimating future heat-related and cold-related mortality under climate change, demographic and adaptation scenarios in 854 European cities. Nat Med 31, 1294–1302. Figure 2.

6. Tamma Carleton, et al, (2022), Valuing the Global Mortality Consequences of Climate Change Accounting for Adaptation Costs and Benefits, The Quarterly Journal of Economics, Volume 137, Issue 4, Pages 2037–2105.

7. Tamma Carleton, et al, (2022), Valuing the Global Mortality Consequences of Climate Change Accounting for Adaptation Costs and Benefits, The Quarterly Journal of Economics, Volume 137, Issue 4, Pages 2037–2105. Figure 3.

8. Tamma Carleton, et al, (2022), Valuing the Global Mortality Consequences of Climate Change Accounting for Adaptation Costs and Benefits, The Quarterly Journal of Economics, Volume 137, Issue 4, Pages 2037–2105. Figure 9.

9. Tamma Carleton, et al, (2022), Valuing the Global Mortality Consequences of Climate Change Accounting for Adaptation Costs and Benefits, The Quarterly Journal of Economics, Volume 137, Issue 4, Pages 2037–2105. Table 2.

10. IPCC (2022), Mitigation Pathways Compatible with Long-term Goals, AR6 Working Group III Report. Box 3.3.

11. Tamma Carleton, et al, (2022), Online Appendix for: Valuing the Global Mortality Consequences of Climate Change Accounting for Adaptation Costs and Benefits, The Quarterly Journal of Economics, Volume 137, Issue 4, Pages 2037–2105. Table F.2.

12. Cross-Chapter Box 1.4 of the contribution of WGI to the 6th Assessment Report provides a detailed explanation of the relationship between the SSPs referred to here and the RCPs referred to in the previous section.