In the second half of last week, Japan experienced warmer air and temperatures that were temporarily on par with March. Tokyo also experienced rainfall for the first time in a long time, since Christmas at the end of last year. Temperatures are expected to drop this week.

Across the ocean, the U.S. has been plagued by drought and wildfires due to the low rainfall over the past few years, and the National Oceanic and Atmospheric Administration (NOAA) has just announced that the amount of damage in 2022 will be the third highest in history. On the other hand, in California, it has been reported that heavy rains have been continuing since the end of the year, causing extensive damage. The rains would normally be a blessing, but the atmospheric river, a long, narrow band of water vapor, is reportedly stagnating, causing successive storms to hit before the moisture in the soil is absorbed, resulting in flooding, landslides and other damage.

Under climate change, the probability of drought and flood extremes is said to increase. The study, published on the Bulletin of the American Meteorological Society (BAMS) website, uses both historical observations and simulation models to examine the 2021-2022 extreme weather events in the United States, the United Kingdom, South Korea, China, and other parts of the world. The study showed that the extreme weather conditions observed in the United States, the United Kingdom, South Korea, China, and other parts of the world in 2021-2022 were highly influenced by human-induced climate change. A study in South Korea found that the average temperature in October 2021 was 3.9°C higher than in 1911-2020, a 1-in-6,250-year event. According to climate change models used in the analysis, such heat waves could become the "new normal" by 2050 unless significant greenhouse gas reduction efforts are made. The 2021 oceanic and terrestrial heat waves that affected people, businesses, infrastructure, and fisheries in Asia, including Japan, South Korea, and China, also estimated that climate change could increase the frequency of such events by 30 times, possibly every 1.5 years by mid-century under a mass greenhouse gas emissions scenario.
　
Even in Europe, where temperatures 5 to 10°C above normal were recorded at the beginning of the year, scientists from the World Meteorological Organization (WMO) say that under climate change, these "rough and brutal" temperature changes could become "the new normal. Climate itself is subject to great variability, but recent extreme weather events cannot be explained by the natural mechanisms of the Earth system, and climatologists around the world believe that the frequency of such extreme weather events is accelerating under climate change.

Contributor: IIYAMA Miyuki (Information Program)