Why are heatwaves getting worse? An expert explains
:: NASA's Scientific Visualization Studio
:: Exeter, England
:: August 6, 2025
:: Raphaelle Haywood, University of Exeter
'Climate change is the main driver of heatwaves and the evidence for that is overwhelming. There is no doubt about that. We have done tons of observations. We have observations, we have models. Everything agrees, the scientific consensus is overwhelming and it's decisive. Right. And we know that as long as we're going to keep burning fossil fuels, we are going to see an increase in temperatures and that's going to make heatwaves more likely and more intense.'
'...And as we burn these fossil fuels, we're releasing carbon dioxide into the atmosphere and carbon dioxide is a really, really potent greenhouse gas.That basically means that when you burn it, when you put it into the atmosphere, it makes the atmosphere warmer.'
'…We're looking in some places at, you know, heatwaves of 40, 45 degrees, almost 50 degrees (Celsius) (122F) temperature, probably more than that in the next 20 years. And we're looking at that being completely normal, you know, by the end of the century, if we don't act on climate change right now.'
Climate change is fueling a range of extreme weather around the world, from flooding and storms to droughts, but the change it is most clearly producing is more extreme heat.
The continued release of planet-heating emissions - largely from the use of coal, oil and gas - will push global temperatures into "uncharted territory" in the coming years, scientists have said.
Heat trapped in the atmosphere by greenhouse gases from burning fossil fuels is raising temperatures to levels unfamiliar to many parts of the world. About 90% of that excess energy - or heat - has so far been absorbed by the world's oceans, moderating temperature increases.
Extreme heat stress has already doubled in the last 40 years, according to the U.S. space agency NASA.
Around 2,300 people died of heat-related causes across 12 European cities during the severe heatwave between June and July, according to scientists at Imperial College London and the London School of Hygiene and Tropical Medicine.
Extreme heat could also spur other types of disasters, from water shortages, worsening droughts, wildfires and biodiversity loss.
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