Has climate change already affected the spatial distribution and temporal trends of reference evapotranspiration in South Korea?

• The objective is to determine whether climate change has caused changes in ETo.
• Changes in spatial distribution and temporal trends of ETo were analyzed.
• Statistically significant differences of ETo due to climate change has occurred.
• Changes in temporal trends of ETo has occurred in various agricultural regions.

Understanding the changes in reference evapotranspiration under climate change is an important component to improve crop management because it is projected to cause potential effects of crop production. Therefore, detecting the changes in the spatial distribution and temporal trends of reference evapotranspiration at the regional and local scale aids in understanding the impacts of climate change and its subsequent effect on hydrology and agriculture. The objective of this study is to determine whether climate change has caused changes in the spatial distribution and temporal trends of reference evapotranspiration in South Korea, and to quantify any abrupt changes and periods of the spatial distribution and temporal trends to compare the statistical significant differences at annual and monthly timescales. The reference evapotranspiration values were determined based on the United Nations Food and Agriculture Organization (FAO) Penman-Monteith equation, using historical weather data for 54 meteorological stations over a 40-year period (1973-2012). Our results showed that statistically significant annual reference evapotranspiration change has occurred in midwest regions with agricultural areas during 1973-1977. Almost agricultural areas in midwest and southwest regions occurred in statistically significant changes of the monthly reference evapotranspiration during February, March and November during the previous two decades (1973-1982 and 1983-1992). These results appear that climate change that have aided significant reference evapotranspiration change in South Korea since the 1970s. Knowledge of long-term spatial distribution and temporal trends of reference evapotranspiration related to climate change would be useful to water resources and agricultural planning.