Projected changes in means and extremes of temperature and precipitation over Thailand under three future emissions scenarios

This study quantifies the potential future changes in temperature and precipitation over Thailand for the mid-21st century years (2031 to 2070) under the 3 emissions scenarios of the Intergovernmental Panel for Climate Change (IPCC; A2, A1B and B1) using fine-resolution (20 km) RegCM3 simulations driven by output of ECHAM5/MPI-OM global climate model experiments. In addition to mean characteristics, 4 temperature extreme indices (numbers of cool days, cold nights, warm nights, and hot days) and 4 precipitation extreme indices (number of consecutive dry days, maximum 5 d precipitation, number of very heavy precipitation days, and precipitation amount due to very wet days) are included. Simulated results over the present year period (1961 to 2000) were also evaluated using surface observations and gridded data. Under all future scenarios considered, it was found that temperature is expected to increase across Thailand by 0.4 to 3.3 degrees C, being most pronounced under A2 and A1B during the summer of the final future decade (2061 to 2070). The South sub-region is least impacted in terms of average temperature. Warm nights and hot days tend to occur more frequently in the future decades while cold nights and cool days occur less. Their trend magnitudes are largest under A2 for cold nights and warm nights, and under A1B for cool days and hot days. For precipitation, a shift to drier conditions was found over the Central-East and South sub-regions in every season under all scenarios and some associated large-scale features were discussed. No substantial changes in average precipitation are seen in the upper sub-regions (the Central-East, North, Northeast sub-regions combined), but less rain is expected for the South in most seasons. Each sub-region tends to experience more consecutive dry days. Trends in the other precipitation indices are increasing in the upper sub-regions. These suggest heavy precipitation and dry spells to be intensified or to occur more frequently in the upper sub-regions.