VANCOUVER, WA – Several large heatwaves the size of Mongolia occurred at the same time almost every day during the warm seasons of the 2010s in the Northern Hemisphere, according to a study led by researchers at Washington State University (WSU).

Using climate data from 1979 to 2019, the researchers found that the number of heat waves occurring simultaneously in the mid to high latitudes of the northern hemisphere was seven times higher in the 2010s than in the years 1980. On average, there were 143 simultaneous heat waves each year in the 2010s, almost every day of the 153 days in the hot months from May to September.

Simultaneous heat episodes also became hotter and more prominent: their intensity increased by 17% and their geographic extent increased by 46%.

“More than one heat wave occurring at the same time often has worse societal impacts than a single event,” said Cassandra Rogers, postdoctoral researcher at the WSU and lead author of the study in Climate Journal. “If some regions depend on each other, for example for agriculture or trade, and both are under stress at the same time, they may not be able to respond to both events. .

Heat waves can cause disasters ranging from crop failures to forest fires. Simultaneous heat waves can multiply these threats, the authors pointed out, draining the ability of countries to help each other in times of crisis, as has been the case with multiple wildfires in the United States, Canada and the United States. Australia associated with the heat waves of 2019 and 2020. A previous study also found that the simultaneous heat waves caused a drop of around 4 percent in global agricultural production.

This study defined large heat waves as high temperature events lasting three days or more and covering at least 1.6 million square kilometers (about 620,000 square miles), which is roughly equivalent to the size of Mongolia or Iran.

The researchers analyzed ERA5 data produced by the European Center for Medium-Range Weather Forecasts, which mixes vast amounts of observational data from land-based weather stations, water buoys and airplanes as well as data from satellites with weather forecast models. ERA5 provides complete aggregate estimates of hourly data for various climate variables starting in 1979, when satellite data became available, which is why the study focused on this period.

Using this observational data, the researchers discovered that the main driver of heat waves was the overall increase in global average temperature due to climate change. The world has warmed by 1 degree Celsius (about 1.8 degrees Fahrenheit) over the past century, with the vast majority of the increase, two-thirds, having occurred since 1975. Researchers have also found that l The increasing occurrence of two hemisphere-wide circulation patterns made it more vulnerable to simultaneous heat waves, including eastern North America, eastern and northern Europe, East Asia and Eastern Siberia.

The study adds more evidence of the need to cut greenhouse gas emissions and mitigate climate change, the researchers said, and the continued rise in temperature means the world should prepare for more. simultaneous heat waves.

“As a society, we are currently not suited to the types of climate events we are currently experiencing,” said co-author Deepti Singh, WSU associate professor at the School of the Environment.

“It is important to understand how we can reduce our vulnerability and adapt our systems to be more resilient to these type of heat episodes which have cascading societal impacts. “

In addition to Rogers and Singh, the study’s authors include Kai Kornhuber of Columbia University, Sarah Perkins-Kirkpatrick of the University of New South Wales in Australia, and Paul Loikith of the State University of Australia. Portland. This research was supported by the National Science Foundation and the Australian Research Council.

– This press release was originally published on the Washington State University website