Temperature and precipitation changes in ten cities in Southeast Asia: an analysis based on CMIP6 climate projections
Authors: Wang Yanxin 
Published: January 2024

Climate change influences both average states and extremes in temperatures and precipitation. Southeast Asia, one of the most vulnerable regions worldwide to floods and heatwaves, indicates an escalation of the possibility of severe climate extremes. Extreme precipitation events can bring increasing floods, leading to considerable damage to property and human well-being. However, droughts also occur in Southeast Asia due to changing precipitation patterns in different regions. In big cities, such damages and risks are highly influential, given the large population density and the proximity to the coast or rivers.Global Earth system models predict the average trends and extremes of the climate system, including record-shattering extreme events that have exceeded previous records. I use the recently released Coupled Model Intercomparison Project Phase 6 (CMIP6), a multi-model large ensemble of climate predictions under different scenarios, to investigate changes in climate conditions in ten highly populated Southeast Asian cities. I first evaluated the CMIP6 simulations in the present day (2005-2014) in the ten cities and found good consistency in temperature and precipitation. Then, I examine changes in the mean, minimum, and maximum temperature and precipitation on an annual, monthly, and daily basis, respectively, under the high-emission SSP5-8.5 scenario. Furthermore, in the late century, annual maximum temperatures hit more than 40 °C in Bangkok, Chiang Mai, and Vientiane. Cities in our study are projected to experience 5-6 °C increases in temperature from November to April, indicating significant changes in the seasonal cycle. Precipitation increases significantly from May to October in most large cities in our study, except for Johor Bahru, Malaysia, where some summer precipitation reductions are expected. Yangon, in particular, is projected to increase more than 4 millimeters per day in July, indicating a very high challenge from flooding as a city facing flood risk every year at present.In summary, our results indicate significant changes in the mean and extreme states of temperature and precipitations in Southeast Asia. Based on these, I identified major physical risks of climate change among the ten cities. Decision-makers should build resilience to these risks to avoid significant damage. Yukiko Hirabayashi et al. (2013) discovered that the risks of floods increase due to the degree of warming. Increasing floods might lead to damage to households and other organisms. Moreover, a greater incidence of climate change, such as droughts, in Southeast Asia is caused by decreasing precipitation in regions (Teerachai Amnuaylojaroen and Pavinee Chanvichit (2019)).This investigation particularly utilizes CMIP6 model simulations to predict the future pattern of climate extremes based on historical and present statistics. CMIP6 performs well in reproducing the climatological spatial distribution of temperature and precipitation, with better performance for temperature than precipitation to predict near future and future climate extremes is that it (Yang et al. for China). With large-ensemble data for climate extremes, CMIP6 can predict more precise climate extremes. This model is necessary for research about extreme climate, as it addresses the climate system's natural variability in different regions with different topographic features.