Assessing Changes in Climate Extremes using CMIP6 and its Implications for Agriculture in the Ganges Delta

Climate extremes are the major concerns due to their impact on agriculture and ecosystem services. This study examined the frequency and spatial extent of 9 climate extreme indices relevant to agriculture in the coastal region of the Ganges Delta in Bangladesh and India. The study was conducted using the latest projected future climate data from IPCC's sixth assessment report (CMIP6, Coupled Model Intercomparison Project Phase 6). Agriculture in the Ganges Delta suffers the most due to less availability of usable water; therefore, the study particularly focused on projected climate changes during the dry season (November-April), at short-term (2021-2040), mid-term (2041-2060) and long-term (2061-2100) basis. The results show an overall increase for both temperature and rainfall, with variations occurring spatially and temporarily. Across the region, projected maximum temperature increases are 1.3°C and 2.2°C for the mid and long-term, respectively under SSP245 (Shared Socioeconomic Pathways). The difference between daily maximum and minimum temperature decreases indicating a higher increase for minimum temperature compared to maximum temperature. At an annual scale, the rainfall increases by 160, 400, and 620 mm under the short, medium and long-term projections, respectively. For the same projection periods, the total rainfall during the dry season rises by 12, 42 and 41 mm respectively. Similar increasing trend was also observed at mid and long-term projections. The intensity of 1-day and 5-day rainfall increases in both short and long-term compared to the historical average rainfall of the region. While total rainfall increases during the dry season, the number of consecutive wet days remains unchanged and the number of consecutive dry days slightly increases across the region. It implies that shorter but more intense spells of rainfall are likely to occur during the dry season in the Sundarbans. The findings of this study are valuable for adaptation and future planning to minimize climate risks to agriculture.