Large, simultaneous heat waves have become much more common in northern regions worldwide due to climate change and could have disastrous consequences, researchers warn.
The investigators also found that these concurrent heat waves are becoming larger and hotter.
"More than one heat wave occurring at the same time often has worse societal impacts than a single event," said lead study author Cassandra Rogers, a postdoctoral researcher at Washington State University (WSU), in Vancouver.
"If certain regions are dependent on one another, for instance for agriculture or trade, and they're both undergoing stresses at the same time, they may not be able to respond to both events," she added in a university news release.
The new analysis of climate data found simultaneous heat waves occurring about six times more frequently in mid- to high-latitudes of the Northern Hemisphere in the 2010s than in the 1980s.
On average, concurrent heat waves occurred on 143 days each year of the 2010s, or nearly every day during the months of May through September, the findings showed.
Compared to the 1980s, simultaneous heat waves were 46% larger and 17% hotter in the 2010s, according to the report published online recently in the Journal of Climate.
A large heat wave was defined as lasting three days or more and covering at least 620,000 square miles, similar in size to Mongolia or Iran.
Heat waves can cause disasters such as crop failures and wildfires. Concurrent heat waves can amplify those threats and exhaust countries' ability to provide mutual aid in such disasters, the researchers noted.
That was the case when multiple wildfires raged through the United States, Canada and Australia during heat waves in 2019 and 2020.
A previous study found that concurrent heat waves led to a 4% drop in global crop production.
Along with providing more evidence about the importance of combating climate change, the new study shows the need to prepare for more concurrent heat waves, the researchers said.
"As a society, we are not currently adapted to the types of climate events we're experiencing right now," said study co-author Deepti Singh, associate professor in WSU's School of the Environment.
"It's important to understand how we can reduce our vulnerability and adapt our systems to be more resilient to these kind of heat events that have cascading societal impacts," Singh added.
The American Red Cross offers a heat wave safety checklist.
SOURCE: Washington State University, news release, Dec. 16, 2021