【動画まとめ】千葉県にレベル5大雨特別警報 「身の安全の確保を」

Recent analysis reveals that extreme compound weather events, like flooding followed by heatwaves, have increased fivefold. These compound disasters are not two separate weather phenomena but a result of a single atmospheric circulation pattern. An expert team asserts that a new system is needed to prepare for such extreme compound events.

Greenpeace disclosed that these compound weather events, such as a storm followed by extreme heat, which occurred once a year in the past, have surged to as often as five days per year recently. This information came from a report titled "Changes in the Risk of Korean Heatwave-Flood Compound Disasters" by the Korean Ministry of Environment, led by Professor Kim Hyung-jun from KAIST's Future Strategy Graduate School.

A compound disaster refers to multiple extreme climate events influencing each other, occurring consecutively or simultaneously. The team compared the six-month (June-September) compound intensity index (CI28) from 1991 to 2020 and 2021 to 2024. The central tendency of the compound intensity index rose from 0.55 over the last 30 years to 1.65 in the recent four years, indicating a substantial increase in disaster severity.

The frequency of these events has also grown. The research found that the number of days experiencing extreme compound events jumped from 12.2 days over the past 30 years to 25 days in the most recent four years, a two-fold increase. The most significant increase occurred with events in the top 10% of the compound intensity index, rising from 12.2 days to 25 days.

The top 5% of days saw a 2.6-fold increase, and the top 1% saw an increase of 4.8 times. The expert team emphasized that what once occurred once a year—extreme weather hazards—has now extended to five days or more in recent years. In Korea and other monsoon climates like Japan, a pattern of heavy summer rains followed by heatwaves has repeatedly been observed.

A high-pressure system over the north Pacific, combined with a low-pressure system over South Asia and another low-pressure system over the Korean peninsula creates a stationary front that generates heavy rains. When this stationary front collapses, a northward shift by a high-pressure system in the northwestern Pacific triggers convective storms and temperature rises, leading to heatwaves.

This same atmospheric circulation system can flip from producing storms to heatwaves within just two weeks. The researchers highlight that as global warming progresses, the transition between heavy rainfall and heatwaves also becomes more rapid. This summer's phenomenon is no different, with intense heatwaves following heavy rains, leaving citizens exposed to both disasters in quick succession.

The Greenpeace campaigner noted that existing response systems for individual disasters like floods or heatwaves are insufficient to handle compound events. He stressed the need for a new, comprehensive preparedness system that accounts for the scale and frequency of compound disasters.