Global life expectancy has more than doubled in just over a century, from around 32 years in 1900 to about 73 years today. This is the result of cleaner water, better nutrition, vaccines and more resilient health systems.

But these gains now face a slower-burning threat: A rapidly warming planet.

Climate change has long been associated with risks such as sea-level rise and biodiversity loss. Now it raises deeper questions of whether future generations will live not only longer lives, but healthier ones – and whether these gains in longevity will be distributed fairly within and between countries.

The World Health Organization estimates that, between 2030 and 2050, climate change could cause about 250,000 additional deaths every year from undernutrition, malaria, diarrhoea and heat stress. This figure does not even fully capture deaths linked to disrupted health services, conflict, forced migration or worsening air quality.

The risks are uneven. Older adults are more vulnerable to heatwaves, air pollution and extreme weather, which increase heart attacks, strokes and respiratory disease. Children are more exposed to undernutrition, infectious diseases and the long-term impact of toxic air on lung and brain development. People in low-income and climate-vulnerable countries often face these threats with the weakest health and social protection systems.

Climate change acts as a risk multiplier on longevity, interacting with existing burdens such as non-communicable diseases, food insecurity and unsafe housing. It threatens to slow, and in some places reverse, the remarkable life expectancy gains of the last century.

A widening longevity gap

These pressures are opening a “longevity gap” both within and between countries.

Data has shown that residents of wealthier, greener neighbourhoods can expect to live close to a decade longer than those in hotter, more polluted or deprived areas. This gap is linked partly to climate and environmental stressors. Low- and middle-income countries, which have contributed least to historical emissions, are already experiencing crop failures, floods and shifting patterns of vector-borne disease that undermine health and nutrition, especially among children.

Rapidly ageing societies, from Southern Europe to East Asia, now face the double challenge of rising numbers of older people and rising climate risks, straining health and care systems. These disparities are moral failures, but they are also macroeconomic risks because climate-sensitive illnesses and productivity losses can erode growth and public finances.