An analysis found that the intensity of "compound disasters," in which heat waves and heavy rain occur one after another due to climate change, has risen sharply in recent years.
Greenpeace said on the 10th that a study it commissioned from Professor Kim Hyeong-jun's research team at the KAIST Moon Soul Graduate School of Future Strategy, titled "Changes in the risk of compound disasters from heat waves and heavy rain in Korea," found that the intensity of compound disasters over the past four years was about three times higher than the average year.
The research team developed the Compound Climate Extreme Intensity Index (CI28), which combines the maximum precipitation and highest temperature over 28 days, and compared summers from 1991–2020 with 2021–2024.
The analysis showed the CI28 median rose from 0.55 in an average year to 1.65 over the past four years. It means the frequency and intensity of heavy rain and heat waves occurring together increased at the same time.
Days with extreme compound disasters also increased. Days in the top 1% by the average-year CI28 standard rose 4.8 times, from an annual average of 1.1 days to 5.2 days. Days in the top 5% or higher increased from 5.5 days to 14.2 days, and days in the top 10% or higher rose from 12.2 days to 25 days.
The research team explained that in recent years, in monsoon climate zones such as Korea and Japan, cases of heat waves following immediately after localized heavy rain have been repeating, making it difficult to view heavy rain and heat waves as separate disasters. They also analyzed that as warming progresses, the transition between the two extreme climates will speed up, potentially increasing the risk of compound disasters further.
Kang Seong-won, a Greenpeace campaigner, said, "With the current system that responds to only one type of disaster, such as heavy rain or wildfires, we cannot prepare for compound disasters," and emphasized, "We need to build a preemptive preparedness system that accounts for the scale and frequency of compound disasters."