Assessing the Impacts of Future Climate Extremes on Boro Rice Cultivation in the Northeastern Haor Region of Bangladesh: Insights from CMIP6 Multi-Model Ensemble Projections

Abstract Northeastern Bangladesh is highly vulnerable to the intensifying impacts of climate change, with extreme climatic events posing a significant threat to rice production. This study examines the projected changes in five key thermal stress indices and heavy rainfall during the rice reproductive phase using 15 global climate models (GCMs) under moderate (SSP2-4.5) and high (SSP5-8.5) emission scenarios. Statistical downscaling and bias correction techniques were employed to generate daily climate data for rainfall, maximum temperature (Tmax), and minimum temperature (Tmin). The Mann–Kendall (MMK) test was applied to identify future trends in these extreme events. The results reveal a substantial decrease in cold stress indices, with three consecutive cold days (CCD3) and six consecutive cold days (CCD6) projected to decline by approximately 9 days. Notably, heat stress indices are anticipated to increase, with hot days (HD) and consecutive hot days (CHD) rising by 18 and 11, respectively. Heavy rainfall days (HR) did not exhibit significant changes. The projected rise in temperatures above 35°C during the rice reproductive phase, encompassing critical stages such as flowering, gametophyte development, anthesis, and pollination and fertilization, suggests adverse consequences for rice yields. These findings underscore the urgency of implementing specific adaptation and mitigation measures to minimize potential yield losses in a future characterized by elevated temperatures. Such measures may include cultivating heat-tolerant rice varieties, adjusting planting windows, and diversifying rice varieties with varying growth durations.