Evaluation and attribution of trends in compound dry-hot events for major river basins in China

Concurrent compound dry and hot events(CDHEs)amplified more damange on the ecosystems and human society than individual extremes.Under climate change,compound dry and hot events become more frequent on a global scale.This paper proposes a mathematical method to quantitatively attribute changes of CDHEs to changes of precipitation,change in temperature and change in the dependence between precipitation and temperature.The attribution is achieved by formulating the total differential equation of the return period of CDHEs among Meta-gaussian model.A case study of China is devised based on monthly precipitation and temperature data during the period from 1921 to 2020 for 80 major river basins.It is found that temperature is the main driving factor of increases in CDHEs for 49 major river basins in China,except for the upper and middle reaches of the Yangtze River.In West China,precipitation changes drove the increase in CDHEs in 18 river basins(23%),particularly in parts of North Xinjiang,Qinghai and Gansu.On the other hand,dependence between precipitation and temperature dominated changes of CDHEs in 13 river basins(16%)of China with other factors,including parts of South China,East China and Northwestern China.Furthermore,changes in both the mean and spread of precipitation and temperature can also contribute to changes in CDHEs.

The half-degree matters for heat-related health impacts under the 1.5℃ and 2℃ warming scenarios: Evidence from ambulance data in Shenzhen, China

The Paris Agreement has prompted much interest in the societal and health impacts of limiting global warming to 1.5 ℃ and 2 ℃. Previous assessments of differential impacts of two targets indicate that 1.5 ℃ warming target would substantially reduce the impact on human health compared to 2 ℃, but they mainly focused on the magnitude of temperature changes under future climate change scenarios without any consideration of greater frequency of cumulative heat exposures within a day. Here we quantified the health risks of compound daytime and nighttime hot extremes using morbidity data in a megacity of China, and also identified the time-period of heat exposure with higher risks. Then we projected future morbidity burden attributable to compound hot extremes due to the half-degree warming. We estimated that the 2 ℃ warming scenario by 2100 as opposed to 1.5 ℃ would increase annual heat-related ambulance dispatches by 31% in Shenzhen city. Substantial additional impacts were associated with occurrence of consecutive hot days and nights, with ambulance dispatches increased by 82%. Our results suggested that compound hot extremes should be considered in assessment of heat-related health impacts, particularly in the context of climate change. Minimizing the warming of climate in a more ambitious target can significantly reduce the health damage.