Characteristics in Regional Climate Change Over South Korea for Regional Climate Policy Measures: Based on Long-Term Observations

We investigated regional climate changes in South Korea over the last 40 years (1980 ~ 2019). The country was divided into 10 areas of Seoul, Gyeonggi, Gangwon, Chungbuk, Chungnam, Jeonbuk, Jeonnam, Gyeongbuk, Gyeongnam, and Jeju. We used the regional climate data (daily temperature and precipitation) measured by Korea Meteorological Administration (KMA) at 61 sites. There has been an annual average temperature increase of 1.4℃ for the last 40 years in Korea, with a range of +1.0℃ (Jeonnam) ~ +1.8℃ (Gangwon). The increases in annual minimum and maximum temperatures were even larger; the increase in annual maximum temperature was as high as 2.2℃ over a broad range of trends (+0.2℃ (Jeonnam) ~ +5.6℃ (Gyeonggi)). The change of annual total precipitation was not clear, but the southern part of Korea showed an increasing trend (Jeju(+206.4 mm/40years)), and the central part of Korea showed a decreasing trend (Chungnam (-119.6mm/40years)). The trend of annual temperature variability was negative in central Korea (Gyeonggi (-4.2℃/40 years)) and positive in southern Korea (Gyeongnam (+1.0℃ /40years)). The changes in the trends of monthly temperature variabilitiy differed by season; March (Gangwon (+0.1℃/40years) ~ Seoul (+3.6℃/40years)) and August (Jeju (-0.9℃/40 years) ~ Chungbuk (+2.9℃/40 years)) showed increasing trends due to the greater increase in maximum monthly temperatures. In comparison, September (Gyeongnam (-0.6℃/40 years) ~ Jeju (-3.5℃/40years)) and December (Seoul (+0.2℃/40 years) ~ Jeonbuk (-4.4℃/40 years)) showed decreasing trends due to the greater increase in minimum monthly temperatures. Those changes might cause different seasonal health impacts. Warming trends were noted in climate extreme indices over the last 40 years. For example, there was an almost one-month increase in the number of summer days (Tmax ≥ 25℃) in Seoul and 15-day increase in the number of tropical nights (Tmin ≥ 25℃) in Jeju. There was a similar decrease (14 days) in cold days (Tmin ≤ -12℃) in Gangwon. Our results show that regional differences in climate change over the last 40 years should be considered for establishing and implementing regional climate change adaptation policies.