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Global warming increases the frequency of fall heatwaves

In October 2021, South Korea experienced an unprecedented heatwave, with average temperatures of 19.9 degrees Celsius – a 3.9C increase above the normal. This event – expected to arise only once in a millennium – was triggered by a delayed appearance of an anomalous high pressure that usually occurs only in the summer, which led to daily maximum temperatures of over 30C in the southern regions of the country, and resulted in major socioeconomic and agricultural losses. A similar event occurred once more in November 2022, increasing public awareness of the increase in frequency of fall heatwaves.

According to a new study led by the Pohang University of Science and Technology in South Korea (POSTECH), the record temperatures from October 2021 would not have occurred without the influence of global warming. 

By using large datasets from CMIP6 global climate models and the U.K. Met Office’s large ensemble simulations, the experts examined how anthropogenic global warming can increase the frequency of fall heatwaves. Moreover, they investigated how often such events may occur during future fall seasons under different greenhouse gas emissions scenarios.

The analysis revealed that, without the major increases in emissions after the industrial revolution, such fall temperatures would have been extremely unlikely to occur. Moreover, the scientists estimated that, if emissions are not urgently curbed, such events may occur once every two years by 2060. However, if the Paris Agreement’s goal of maintaining average global temperatures under 2C above pre-industrial levels is reached, extreme fall heatwaves would happen only once every 30 or 40 years.

“As unprecedented high temperatures during fall are occurring more frequently, it is necessary to provide an accurate prediction of their near-term occurrences and also prepare corresponding adaptation measures to minimize associated damages in all socioeconomic fields,” concluded co-author Seung-Ki Min, a professor of Environmental Science and Engineering at POSTECH.

The study is published in the journal Bulletin of the American Meteorological Society. 

By Andrei Ionescu, Staff Writer

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