For the assessment of the future flood risk of 26 watersheds in South Korea, we analyze the change in extreme precipitation with a 100-year return period under global warming. We use downscaled high-resolution observation and bias-corrected future climate change scenario data from the National Institute of Meteorological Sciences for this purpose. In the high-CO₂ emission scenario (SSP5-8.5), the average rates of change in 100-year return period precipitation at 26 watersheds is projected to increase about 29%, 46%, and 53% in the early (2021 ~ 2040), mid (2041 ~ 2060), and late (2081 ~ 2100) 21st century, respectively, relative to the present climate. The number of watersheds with a 100-year return period precipitation increase of 50% or more compared to the present climate is predicted to increase significantly in the late 21st century. On the other hand, in the low-CO₂ emission scenario (SSP1-2.6), after the mid-21st century, the increase in 100-year return period precipitation is much less than that of the high-CO₂ emission scenario since the rate of change is projected to increase about 31%, 31%, and 29% in the early, mid, and late periods, respectively. Furthermore, most watersheds show a 100-year return period precipitation increase of 50% or less. These results imply that the possibility of flooding by extreme precipitation can be reduced through achievement of a carbon-neutral policy.

Recently, the CORDEX-East Asia team completed climate change simulations based on five regional climate models (RCM) under four Shared Socioeconomic Pathways (SSP) scenarios. In this study, the performance of five RCMs and their ensemble averages for present-day climate simulations are evaluated. All RCMs have relatively high performance for climatology patterns for Korea, East China and Japan, while relatively low performance is observed for the Tibetan plateau. Many RCMs share cold and wet biases. Future climate changes under four SSP scenarios are analyzed for the end of 21st century (2081 ~ 2100) compared to present day (1995 ~ 2014). East Asia is expected to experience temperature increases of 2.4℃ to 6.2℃ and precipitation increases of 6.7% to 12.6%, with stronger changes in higher-emission scenarios. Among the five RCMs, HadGEM3-RA projects the largest increase in temperature while GRIMs is characterized by the strongest increase in precipitation. In line with mean warming rates, warm extreme days (TX90p) are projected to increase by 35.7 ~ 93.3 days and cold extreme days (TN10p) are projected to decrease by 23.4 ~ 35.2 days. The results of this study can be used as a reference for future detailed analyses of East Asian climate change and its impacts as well as for emphasizing the importance of carbon neutrality.

In this study, we projected climate change by region over South Korea under Global Warming Levels (GWL) of 1.5, 2.0, and 3.0°C using new high-resolution (1 km) simulations. We combined 5 Regional Climate Models (RCMs) and 4 Shared Socioeconomic Pathways (SSPs) and used them for future projection. The findings indicate that, as global warming progresses, the annual mean temperature in South Korea will increase by +0.7, +1.4, and +2.6°C, respectively, compared to present-day (2000 ~ 2019). There is no significant change in total precipitation under the 1.5°C GWL condition. However, an increase of +4.0% (+5.8%) is expected under the 2.0°C (3.0°C) GWL condition, with a significant increase in precipitation expected during the months of July to September. The study also finds that extreme high-temperature indices are projected to increase more significantly than the annual mean temperature, suggesting that future annual temperature ranges may increase. Additionally, extreme climate indices for precipitation are projected to increase unless GWL is limited to 1.5°C, with a notable impact in the Jeju area. The results of this study are expected to be used as fundamental data for establishment of national climate change adaptation policies aimed at achieving carbon neutrality.

Five regional climate models (RCMs)—CCLM, RegCM, HadGEM3‐RA, SNURCM and WRF—participating in the Coordinated Regional Climate Downscaling Experiment‐East Asia (CORDEX‐EA) Phase 2 project are evaluated for their ability to simulate spatiotemporal variability in Asian summer precipitation. For this purpose, two dynamical downscaling sets, experiments forced by ERA‐Interim reanalysis data (reproduction experiment) and historical data from three Coupled Model Intercomparison Project 5 (CMIP5) general circulation models (GCMs) (historical experiment) are analysed. The horizontal resolution of the downscaled results is 25 km, and the analysis period is from 1981 to 2005 (25 years). The RCMs show reasonable performance in simulating the spatial and temporal characteristics of summer precipitation in CORDEX‐EA Phase 2 domain. To assess spatiotemporal patterns in Asian precipitation, cyclostationary empirical orthogonal function (CSEOF) analysis is used. In the first mode representing seasonal variations, the model ensemble results of both the reproduction experiment (Rep_ENS) and the historical experiment (His_ENS) simulate the peak times, location of precipitation and progression of the monsoons in Asia reasonably. Their features are greatly influenced by the moisture flux, indicating that the relation between precipitation and 850 hPa moisture flux is depicted well by RCM ensembles. In the second mode, which represents intraseasonal variations, the Rep_ENS depicts the western North Pacific summer monsoon break (WNPSM break) phenomenon similar to the observation. Although the His_ENS simulates the WNPSM break later than the observation, it does present the intraseasonal variation in the East Asian summer monsoon region. Based on these results, the five RCM ensemble results show the ability to capture spatiotemporal characteristics of summer precipitation in CORDEX‐EA Phase 2 domain, as well as added value from dynamical downscaling.

Among the various thermal stress indices, apparent temperature (AT) is closely related to public health indicators, and consequently is widely used by weather agencies around the world. Therefore, in this paper we estimate the changes in AT and contributing components in Korea as a whole and in five major cities (Seoul, Gwanju, Daegu, Daejeon, and Busan) using national standard climate scenarios based on the coupled model inter-comparison project (CMIP6). In the present day, high AT occurs in major cities due to high temperature (TAS) and relative humidity (RH). Our findings reveal that even when TAS is relatively low, large AT occurs with higher humidity. Notably, in future warmer climate conditions, high AT may first appear in the five major cities and then extend to the surrounding areas. An increase in TAS and RH during the pre-hot season (March to June) may lead to earlier occurrence of thermal risks in future warmer climate conditions and more frequent occurrence of high thermal stress events. Our study can serve as a reference for future information on thermal risk changes in Korea. Considering those who have not adapted to high temperature environments, our findings imply that thermal risks will become more serious and that heat adaptation strategies will be needed during the pre-hot season under future warmer climate conditions.