Projected Change On Multi-year Annual Extreme Of Daily Heat And Precipitation Events In China

Human activities have led to global warming,resulting in more frequent occurrence of extreme weather and climate events with serious impacts on social and natural systems over global various regions.In particular,impacts of multi-year extreme events have devastated.As one of the regions affected most by global climate change,China has also shown an increasing trend of extreme heat or precipitation events in recent years.Therefore,it is urgent to project changes and quantify the impacts on multi-year extreme heat and precipitation events in China under the future global warming levels.It is important in formulating climate change response strategies scientifically.In this dissertation,we use multi-model ensemble for daily maximum temperature and precipitation derived from the Coupled Model Intercomparison Project Phase 6(CMIP6)simulation.Based on the generalized extreme value distribution(GEV)function of extreme theories,we derive the intensity and frequency changes on 2-50 yr extreme heat and precipitation events by adopting the probability weighted moment(PWM)method to estimate key GEV parameters.Time slice sampling method is used to select the corresponding years of warming threshold.Four warming levels(1.5°C,2.0°C,3.0°C,and 4.0°C)above preindustrial compared to present-day climate(1.0°C)are considered.We also analyze the sensitivity of projected changes to Shared Socioeconomic Pathways(SSP1-2.6,SSP2-4.5,SSP3-7.0,and SSP5-8.5).Considering China's vast territory,diverse climate,and the fact that provincial administrative regions are the most important administrative units in China,we select 32 provinces(excluding Hong Kong and Macau)in China as projected units,and assess the differences under the risks of multi-year extreme heat and precipitation events on each unit,from the perspective of impacts in extreme event changes on population exposure.The study aims to provide a more guiding scientific basis for national and local governments to formulate climate change policies.The main conclusions are as follows.(1)As global warming intensifies,the intensity of daily extreme heat and precipitation events increase significantly across Chinese provinces and show significant regional variability.For instance,at 2?,which is the control target suggested by the Paris Agreement,50-year extreme daily heat events will increase by0.98-1.84°C,respectively,relative to the current climate state.The changes on intensities of multi-year extreme heat events are similar and greater than the increase of average air temperature regardless of recurrence period.For multi-year extreme precipitation events,the intensities with a recurrence period of 50 years will increase4.3-10.3%,constant with the ability of holding atmospheric water indicated by Clausius-Clapeyron relation(7%/°C).Northwestern and northeastern provinces have higher changes in heat intensity than other provinces;southern provinces have relatively smaller changes in precipitation intensity,while north-south regional differences narrow significantly as precipitation extremes increase.(2)Extreme daily heat and precipitation events will be more frequent as the level of global warming increases,showing significant regional variability.Specifically,when the global warming reaches to 2?,the current average 50-year extreme daily heat event will become a 4.2-to 13.2-year event;the occurrence period of extreme daily precipitation event will change from the current average 50 years to 25.7-38.8 years.The frequency variation of daily heat extreme events in the north is relatively small,and the regions with large variation in the frequency of daily precipitation extremes are mainly concentrated in the eastern coastal provinces.In addition,the frequency changes of both extreme heat and precipitation show a non-linear increase with increasing event extremes.(3)When considering the impact of extreme daily high temperature and precipitation intensity and frequency changes on population exposure,the eastern provinces with constantly larger population in the future,are projected to suffer increasing risks than westerns at higher warming levels.It indicates that even there are regional differences in extreme temperature and precipitation changes in China in the future,for example,the arid northwestern is the hot spot for increasing and enhancing extreme heat,eastern should continue to a priority region for climate change response action.(4)The choice of socio-economic development paths will not qualitatively change the above conclusions,although it will significantly affect the arriving year of a certain level of global warming.For instance,the maximum difference of the center year reaching to 2.0°C under different socio-economic development paths,is estimated to be maximum 20 years according to the French CNRM-CM6-1.