The relationship between climate variables (e.g., precipitation and temperature) and crop yield has been used to assess the impacts of climate extremes (e.g., droughts, heatwaves) on crop yield, which is commonly assumed to be time-invariant. However, climate-yield relationships may change over time due to the influence of global warming and human interventions. In particular, the concurrent changes in the precipitation-yield relationship and the temperature-yield relationship could pose challenges to the development of adaptation measures for agriculture planning and management. The objective of this study is to propose a statistical approach to estimate the risk of crop yield reduction under the dry condition, hot condition, and compound dry-hot condition due to concurrent changes in climate-yield relationships. Results show that the relationship between climate and maize yield in the top ten maize-producing countries has changed from 1961-1988 to 1989-2016. The risk of crop yield reduction generally increases with enhanced dependence between dry conditions and crop yield (or hot conditions and crop yield). Based on the multivariate distribution, results show that the risk of maize yield reduction increases for the majority of these countries under compound dry-hot conditions due to concurrent changes in climate-yield relationships. Results of this study are expected to provide useful insights for assessing agriculture vulnerability under global warming.

气候变量（例如降水和温度）与农作物产量之间的关系已用于评估极端气候（如干旱，热浪）对农作物产量的影响，通常认为农作物产量是随时间变化的。但是，由于全球变暖和人为干预的影响，气候-产量关系可能会随着时间而改变。特别是，降水-产量关系和温度-产量关系的同时变化可能对制定农业计划和管理适应措施构成挑战。这项研究的目的是提出一种统计方法，以估计由于气候与产量关系的同时变化而在干旱，炎热和复合干热条件下作物减产的风险。结果表明，从前十个玉米生产国来看，气候与玉米产量之间的关系从1961-1988年变为1989-2016年。随着干旱条件和农作物产量（或炎热条件和农作物产量）之间的依赖性增强，农作物减产的风险通常会增加。根据多变量分布，结果表明，由于气候-产量关系的同时变化，在复合干热条件下，这些国家中大多数国家的玉米减产风险增加。预期这项研究的结果将为评估全球变暖下的农业脆弱性提供有用的见解。随着干旱条件和农作物产量（或炎热条件和农作物产量）之间的依赖性增强，农作物减产的风险通常会增加。根据多变量分布，结果表明，由于气候-产量关系的同时变化，在复合干热条件下，这些国家中大多数国家的玉米减产风险增加。预期这项研究的结果将为评估全球变暖下的农业脆弱性提供有用的见解。随着干旱条件和农作物产量（或炎热条件和农作物产量）之间的依赖性增强，农作物减产的风险通常会增加。根据多变量分布，结果表明，由于气候-产量关系的同时变化，在复合干热条件下，这些国家中大多数国家的玉米减产风险增加。预期这项研究的结果将为评估全球变暖下的农业脆弱性提供有用的见解。