Study finds most intense heatwaves ever across globe

A study, led by the University of Bristol, has identified the most intense heatwaves ever on earth, many of which went unnoticed at the time.

Researchers have also shown how heatwaves are projected to get even worse as the climate crisis worsens.

Last summer’s record-breaking heatwave reached an all-time Canadian high of 49.6 degrees in Lytton, British Columbia on June 29, an increase of 4.6 degrees from the previous peak.

This was the deadliest weather event ever in Canada, resulting in hundreds of fatalities and raging wildfires leading to infrastructure damage and loss of crops.

However, scientists have uncovered five other heatwaves around the world which were more severe and went largely unreported.

The study calculated how extreme heatwaves were relative to the local temperature and discovered the top three hottest-ever in the respective regions.

These were in Southeast Asia in April 1998, hitting 32.8 degrees, Brazil in November 1985, peaking at 36.5 degrees, and Southern USA in July 1980 when temperatures hit 38.4 degrees.

Lead author, climate scientist Dr Vikki Thompson at the University of Bristol, said: ‘The western North America heatwave will be remembered because of its widespread devastation. However, the study exposes several greater meteorological extremes in recent decades, some of which went largely under the radar likely due to their occurrence in more deprived countries. It is important to assess the severity of heatwaves in terms of local temperature variability because both humans and the natural eco-system will adapt to this, so in regions where there is less variation, a smaller absolute extreme may have more harmful effects.’

The team behind the study also used climate model projections to predict future heatwave trends and found heatwave intensity is set to rise in line with increasing global temperatures.

Improving understanding of climate extremes and where they have occurred can help to prioritise measures and where they should be implemented to tackle the climate crisis in the most vulnerable regions.

Co-author Professor Dann Mitchell, Professor in Climate Sciences at the University of Bristol, said: ‘Climate change is one of the greatest global health problems of our time, and we have showed that many heatwaves outside of the developed world have gone largely unnoticed. The country-level burden of heat on mortality can be in the thousands of deaths, and countries which experience temperatures outside their normal range are the most susceptible to these shocks.’

Photo by Oleksandr Sushko