With 2024 marking the hottest year on record, and the planet for the first time breaching 1.5 °C of warming from pre-industrial temperatures, it’s urgent to consider how climate change will affect human health in the long term. The consequences for our bodies of repeated exposure to heat, drought and wildfire smoke will mount. But climate assessments are not yet taking this into account.
Some effects of climate change can clearly be associated with health consequences. It’s possible to track deaths from heat stroke, such as the more than 1,000 fatalities that occurred during the pilgrimage to Mecca in Saudi Arabia last June. It’s also straightforward to measure the toll on elderly people and babies in the weeks after a heatwave, when their bodies have struggled to cope with the stress on hot days and been unable to recover during hot nights.
Earth shattered heat records in 2023 and 2024: is global warming speeding up?
But there’s a cumulative, longer-term toll, and this needs to be studied more.
For example, years of regular exposure to heatwaves and droughts can lead to kidney disease through successive bouts of dehydration and electrolyte imbalances. Poor-quality sleep, which is common on hot nights, is linked to decreased physical and mental health, cognitive decline and compromised immune function, all of which can accumulate over time. The development of fetuses is affected by the conditions that they and their mothers are exposed to and will have an impact on their future health.
At the fundamental level, gene expression can be altered by environmental stressors. For example, studies show1 that people who were exposed to bouts of hot, dry weather while in the womb have an increased likelihood of high blood pressure as adults, decades on. There are many consequences of a warming global climate that researchers are yet to understand, and more we do not even know about.
It can be extremely hard to quantify health burdens that do not immediately follow exposures, even though we know they are there. They are obscured by patchy health data and variations in people’s exposure to stressors, even when the physiology involved is reasonably well understood.
Researchers and public-health officials need to be clear in climate-impact assessments that the burden of death and illness is likely to be much greater than current models can quantify. Several issues need to be thought through.
Extreme heat harms health — what is the human body’s limit?
