A team of researchers from the University of Bristol, UK, identified the most intense heat waves ever recorded around the world, according to a study published in Science Advances. Surprisingly, some of them were never identified as heatwaves when they happened. What’s more, the team speculates that heat waves will get hotter as climate change worsens.
Last summer, we had the Western North America heatwave, with a record-breaking high of 49.6 °C in Lytton, British Columbia, Canada, on June 29th. This was an increase of 4.6 °C compared to the previous peak.
In addition to this heatwave, the new study has uncovered five other events around the world which were even more severe but were never reported. “The recent heatwave in Canada and the United States shocked the world. Yet we show there have been some even greater extremes in the last few decades. Using climate models, we also find extreme heat events are likely to increase in magnitude over the coming century – at the same rate as the local average temperature,” said lead author, climate scientist Dr. Vikki Thompson at the University of Bristol.
Heatwaves can be extremely devastating and destructive. For example, the Western North America heatwave was the most deadly weather-related event ever in Canada, and resulted in hundreds of fatalities. The wildfires caused by the heatwave also lead to the loss of crops, wildlife, and infrastructure.
Now, UK researchers identified heatwaves by comparing maximum temperatures and normal local temperatures within the same period (not necessarily summer). Using this approach, they found three heatwaves in Southeast Asia in April 1998, which hit 32.8 °C; Brazil in November 1985, peaking at 36.5 °C; and Southern USA in July 1980, when temperatures rose to 38.4 °C.
“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,” said Dr. Vikki Thompson, from the university’s Cabot Institute for the Environment.
The researchers also used climate model projections to speculate how heatwaves are likely to develop in the future. The results show that heatwaves are likely to get more intense as climate change get worse.
The highest temperatures during heatwaves don’t necessarily mean they’ll cause the most significant impacts, but most of the time, they’re connected. For the authors, this means that improving our understanding of how these heatwaves develop and where they may occur can help establish policies to tackle them, especially if they occur in vulnerable regions.
“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,” concluded Professor Dann Mitchell, Professor in Climate Sciences at the University of Bristol and co-author in the study.
Thompson V, Kennedy-Asser AT, Vosper E, Lo YTE, Huntingford C, Andrews O, Collins M, Hegerl GC, Mitchell D (2022) The 2021 western North America heat wave among the most extreme events ever recorded globally. Sci Adv. 8(18):eabm6860. doi: 10.1126/sciadv.abm6860.