Heatwaves around the world increase

Researchers at the ARC Centre of Excellence for Climate Extremes, administered by The University of New South Wales, have conducted the first comprehensive worldwide assessment of heatwaves – revealing that in nearly every part of the world, heatwaves have been increasing in frequency and duration since the 1950s.

The research has also produced a new metric, cumulative heat, which reveals exactly how much heat is packed into individual heatwaves and heatwave seasons. As expected, that number is also on the rise.

In Australia’s worst heatwave season, an additional 80°C of cumulative heat was experienced across the country. In Russia and the Mediterranean, their most extreme seasons baked in an additional 200°C or more.

‘Not only have we seen more, and longer, heatwaves worldwide over the past 70 years, but this trend has markedly accelerated,’ says ARC Future Fellow, Dr Sarah Perkins-Kirkpatrick. ‘Climate scientists have long forecast that a clear sign of global warming would be seen with a change in heatwaves.’

The study also identified that heatwaves are quite sensitive to internal climate variability at regional levels. This variability can overwhelm heatwave trends, so regional trends shorter than a few decades are generally not reliable.

To detect robust trend changes, the researchers looked at how the trends had changed over multi-decade intervals between 1950-2017. The changes were stark.

‘The dramatic region-by-region change in heatwaves we have witnessed over the past 70 years and the rapid increase in the number of these events, are unequivocal indicators that global warming is now with us and accelerating.’

	THE RESEARCHERS SAY THAT WHETHER OR NOT THESE CHANGES ARE RAPID OR SLOW, IT SEEMS INEVITABLE THAT VULNERABLE NATIONS WITH LESS INFRASTRUCTURE WILL BE HIT HARDEST BY EXTREME HEAT.

 

Image: Global maps of cumulative heat statistics. Credit: Perkins-Kirkpatrick and Lewis, 2020, Nature Communications.