Researchers are sounding the alarm: heat waves are becoming more intense around the world

Researchers are sounding the alarm
Heat waves are intensifying around the world

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Temperatures are rising due to man-made climate change. It's not just the number of heat waves that are increasing around the world. Weather extremes are also becoming increasingly longer and slower — “with more devastating impacts on natural and social systems,” a new study shows.

Major heat waves last longer and move more slowly over land. This is what Chinese and American scientists have concluded from an analysis of climate monitoring data from 1979 to 2020. Using computer simulations based on the data, the researchers show that increases in human-made greenhouse gases in the atmosphere play a significant role. This development.

“If greenhouse gas emissions continue to increase, long-lasting and slow-moving large continuous heat waves will have more devastating effects on natural and social systems in the future,” writes a team led by Ming Luo of Sun Yat-sen University in Guangzhou. In Special Issue “Scientific Advances”.. Luo and colleagues evaluated three large data sets based on meteorological observations, mostly via satellite. The global analysis includes anticyclones that caused heat waves over at least one million square kilometers – almost twice the area of ​​Spain.

Between 1979 and 1983 there was an average of 75 such heat waves per year, but between 2016 and 2020 there were 98. Not only that: the average affected area worldwide has increased by 952,000 square kilometers per decade.

High latitudes in the Northern Hemisphere are particularly affected

That's not all: the global average duration of a heat wave was a good 8 days between 1979 and 1983, and a good 12 days between 2016 and 2020. The rate of increase was particularly high in Europe and Asia at 1.15 days per decade. At the beginning of the study period, the average speed of heat waves was about 350 kilometers per day. Depending on the data set, it has decreased by an average of 7 to 9 kilometers per day per decade.

Atmospheric blocking is becoming more common, especially in the high latitudes of the Northern Hemisphere, Luo's team writes, where a high-pressure area reaching high altitudes blocks the drift of typical westerly winds. Low pressure areas moving with westerly winds should then move around a constant height.

The scientists used their data for simulations in a climate model (CMIP6; Coupled Model Intercomparison Project). The speed of the heat wave peak in this simulation with increasing atmospheric greenhouse gas levels over a decade was 8.43 kilometers per day, more than twice that of the simulations with natural drivers (4.18 kilometers per day). Researchers conclude that man-made climate change is contributing heavily to slower heat waves.

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