Projected changes in the near-future mean climate and extreme climate events in northeast Thailand

This study provides an assessment of changes in mean and extreme climate in northeast Thailand, focusing on the near-future period (2021-2050). Spatiotemporal changes in climate extremes and return values are investigated compared to 1981-2010. Climate model-related uncertainties are quantified using 14 models from the Coupled Model Intercomparison Project phase 5 (CMIP5) and 8 models from phase 6 (CMIP6). CMIP6 models have a higher sensitivity to external forcings as the CMIP6 ensemble suggests an increase in maximum and minimum temperatures by 1.45 degrees C (0.8-1.9 degrees C) and 1.54 degrees C (1.1-1.9 degrees C) under the high emission scenario, which is greater than by CMIP5 ensemble: 1.10 degrees C (0.5-1.7 degrees C) and 1.13 degrees C (0.7-1.6 degrees C), respectively. No significant changes in annual rainfall are projected, although it will be temporally more uneven with decreases (6-11%) during the pre-rainy season (March-May) and increases (2-8%) during the rainy season (June-October). The bootstrap analysis technique shows the inter-model uncertainties for rainfall projections in CMIP6 have reduced by 40% compared to CMIP5. The annual number of hot days will increase more than twofold and warm nights, more than threefold. Near-future will experience an increase in the rainfall intensity, a decrease in the number of rainy days, and an increase in the 20-year return values of annual maximum 1-day rainfall and consecutive 5-days rainfall (>30%). In addition, the rainy season will be shortened in the future as onset and retreat are delayed, which may have implications in agricultural activities in the basin since cultivation is primarily rainfed. These findings suggest that anthropogenic activities will significantly amplify the climate extremes. The study results will be useful for managing climate-related risks and developing adaptation measures to improve resilience towards potential climate hazards.