For weeks people in South Asia have been suffering from a strong heat wave, on some days the air temperature has reached 50 degrees Celsius in the region. Even at night it hardly cools down, which affects health and is likely to lead to numerous deaths. The heat wave in India and Pakistan is part of a series of such extreme weather events: in the summer of 2021, the north-west of the USA and western Canada were glowing, and in early 2022 the thermometer in Argentina rose to record values. A study by Vikki Thompson from the University of Bristol and her team in “Science Advances” has identified some of the most extreme heat waves in recent decades, some of which have received little attention in the media.
For example, the temperature in Lytton, Canada rose to 49.6 degrees Celsius on June 29, 2021, beating the previous record in the region by 4.6 degrees Celsius. The highest daily average was still 39.5 degrees Celsius. However, this event was trumped by various heat waves, in which the standard deviation from the average temperatures of the respective seasons was even higher than in Canada. In Southeast Asia in April 1998 with 32.8 degrees Celsius, in Brazil in November 1985 with 36.5 degrees Celsius and in the south of the USA in July 1980 with 38.4 degrees Celsius (each maximum temperature), the values were sometimes more than five units above the previous peaks in these regions: significant jumps, even if the maximum temperatures remained below those in Canada or currently in South Asia.
»The heat wave in western North America will be remembered for its extreme consequences. However, our study uncovers several major meteorological extremes over the past few decades, some of which have largely remained under the radar, likely because they occurred in poorer countries. It is important to assess the severity of heatwaves based on local temperature variations, as both humans and natural ecosystems adapt to them. So in regions with less variability, even a smaller absolute maximum can have a larger impact,” says Thompson.