How Significant is Projected Drought Risk in Pakistan Under a Warmer Climate?

Climate change in mean-state or variation could contribute to more/less occurrence of severe drought. Assessing the future drought risk in the warming climate under the multivariate framework is crucial for helping policy-making to combat the long-term drought risk and water crises. Here, we investigated the multivariate future drought risk under global warming targets using different methods, including run theory, joint return levels, contributing climate factors, and population exposure across Pakistan subregions. We used 23-global climate models from the CMIP6 two scenarios (shared socioeconomic pathways (SSPs), SSP2-4.5, and SSP5-8.5) and population projection across Pakistan and its subregions under 1.5 degrees C and 2 degrees C of global warming targets. The SPEI (Standardized Precipitation Evapotranspiration Index) is employed as a drought index, and its characteristics were assessed using run theory. Under the copula framework, the drought severity and duration were jointly quantified to explore the return periods. Changes in population exposure and its influencing contributors are computed across Pakistan and its selected subregions (henceforth, R1, R2, R3, and R4). Results indicated that R1, R3, and R4 will likely experience significant changes in extreme drought events to the exposed population. The occurrence of historical bivariate 50-year droughts might double over 60% of regional land areas under 1.5 degrees C warming, attributing more intensified drought episodes under 2.0 degrees C warming relative to the recent climate. Amongst subregions, the population exposure in R3 and R4 is projected to be influenced by accelerating drought risks under warming of 1.5 degrees C. Regarding half-degree less, results reveal that limiting global warming to 1.5 degrees C relative to 2.0 degrees C might decrease the frequency of extreme droughts by 10% to 60%. Future changes in regional exposure would primarily lead to the interaction effect; however, the population effect is more significant than the climate, particularly in R2 and R3. As a result, a regional perspective is critical for providing actionable information and assisting communities in adapting to climate change impacts specific to their location.