High sea surface temperatures and vertical wind shear (change in wind direction and speed with altitude): this was the reason why Typhoon No. 11 Hinnamnor grew stronger as it approached land, according to the Korea Meteorological Administration.

At first sight, these conditions seem to describe the current condition of the atmosphere, but they are closely related to climate change. Warmer temperatures in the North Pole tend to weaken the jet stream and the vertical wind shear. Several studies on typhoons warn that such changes in our climate can create more powerful typhoons than in the past and will contribute to the development of even stronger typhoons in the future.

According to the study, “Changes in the extreme values of meteorological elements of typhoons affecting the Korean Peninsula based on observational data” released last October by Jung Woo-sik, a professor in the department of atmospheric environment information engineering at Inje University, typhoons have recently grown stronger. Jung studied the changes in extreme values in typhoon observations from 1904, when the modern definition of meteorological observation began, to 2020.

Typhoon damage occurs more often when there are “extreme” values. The lower the atmospheric pressure of the typhoon, the higher the instantaneous wind speed, the more concentrated the rainfall, the bigger the damage.

Jung’s study divided the years into four time periods, starting with Period 1, which lasted from 1904 until 1930. He then divided the following years until 2020 into three periods, Period 2-4, each thirty years long. As the time flowed from Period 1 to Period 4, the extreme value of the atmospheric pressure at the typhoon’s center grew smaller, and the maximum wind speed, the maximum instantaneous wind speed, and accumulated rainfall all increased.

“Autumn typhoons also increased in frequency and power. In another study that Jung participated in, “Fall typhoons affecting the Korean Peninsula! Changes in characteristics from past to present,” among the typhoons that affected the Korean Peninsula from 1954 to 2003, 20% occurred in September and October. But from 2002 to 2019, the figure increased to 31.6%. Unlike the popular understanding that typhoons come in the summer, more and more typhoons are coming in the fall.

The maximum instantaneous wind speed of autumn typhoons also continued to increase. The strength of a typhoon is expected to become more powerful as the world emits more and more greenhouse gases. “Future change in tropical cyclone activity over the Western North Pacific” a study released in the Journal of Climate published by the American Meteorological Society in 2019 predicted that in a regional climate model (RCM) where the world emits greenhouse gases at a rate similar to the present (RCP8.5), the accumulated cyclone energy (ACE) of tropical cyclones heading toward East Asia would increase 45.9% in 2024-2049[KS1] compared to 1980-2005. The accumulated cyclone energy (ACE) is an indicator that comprehensively takes into consideration the frequency, duration, and strength of tropical cyclones.

If the world continues to emit greenhouse gases at the current rate, more typhoons may head toward the Korean Peninsula even if the number of typhoons drops. The number of tropical cyclones that occur in the subtropical low latitude regions may fall, but there will be more typhoons that occur in 20-25°North, and these typhoons are more likely to head toward Korea.

In the RCP 8.5 model, the number of tropical cyclones heading toward East Asia (South Korea, China, Japan) will increase 17% in 2024-2049 compared to 1980-2005. Cha Dong-hyun, a professor of urban and environmental engineering at the Ulsan National Institute of Science and Technology said, “If the North Pacific High expands due to global warming, it can block the typhoons’ path toward Japan and direct them toward South Korea.”