Increasing Exposure of Cotton‐Producing Regions to Heat During Critical Growth Stages Under Projected Warming Scenarios in Xinjiang, China

ABSTRACT Cotton cultivated in Xinjiang accounts for more than 90% of its production in China, equivalent to 22% of global production. Given the rapid warming rate, the extent to which cotton cultivation is exposed to heat, particularly during critical growth stages, remains uncharacterized. To settle this issue and propose potential adaptation measures, we evaluated the exposure of cotton cultivation to heat during the flowering and boll development stages in Xinjiang, and checked mitigation availability by changing the onset of flowering time. We employed extreme degree days (EDD, d·°C) and accumulated heat stress days (AHSD, d) to depict the spatiotemporal patterns of such exposure over the historical period (1961–2020) and two different warming scenarios (1.5°C and 2.0°C). The results revealed a modest upward trend of heat exposure during the critical growth stages, characterised by considerable interannual variability. Specifically, EDD and AHSD increased at 0.12 d·°C·a −1 and 0.12 days·a −1 , respectively. Despite notable spatial heterogeneity, regions such as Hami, Paotai, Yuli, and Mossel were identified as the most vulnerable, with EDD exceeding 25 d·°C and AHSD surpassing 9 days. Future projections suggest a substantial intensification of heat exposure, with EDD and AHSD values tripling and doubling under the 2.0°C warming scenario. Our findings highlight the critical importance of optimizing growth stage windows to reduce cotton's exposure to heat. Adaptive measures, such as adjusting planting windows and breeding new cultivars, are urgently needed to mitigate the negative climate impacts and ensure cotton productivity.