Population Exposure To Precipitation Extremes In The Indus River Basin Under The Different Warming Targets

Since the Industrial Revolution,global climate change characterized by warming has posed great challenges to today's society.Climate change may increase the frequency and intensity of extreme events,and the basic characteristics such as the scope and duration of impact may be significantly changed.With the rapid development of social economy,the impact of future extreme events may be more serious.Extreme precipitation event(EPE)is one of the most frequently and seriously disasters in the world.Located in the South Asia,the Indus River Basin is one of the seriously areas being affected by EPE.From the perspective of the disaster impact,it is very important to identify extreme precipitation events three-dimensionality which by intensity-impact area-duration to quantitatively assess the population exposure of extreme precipitation events,and to formulate disaster prevention and mitigation policies for regional sustainable development.In addition,the formal implementation of the Paris Agreement provided new opportunities and challenges for the international community to cope with climate change.The research on disaster risk of extreme events under different warming targets can provide scientific basis for climate policy including temperature rise target selection and socio-economic development policy formulation.The main results of this paper are as follows:(1)Areal averaged annual mean temperature have shown a significant increase trend in the IRB,and the most obvious increase was in the early 21 st century.Unlike monotonic increase of temperature,annual precipitation has shown a less-more-less-more decadal oscillation.Spatially,increases of seasonal and annual temperature were significant at 95% confidence level over the IRB except for the small fraction of northwestern region.Especially,warming is the sharpest in the southern plain and the northeastern mountain regions.In the same period,annual and wet seasonal precipitation along the southeast to northwest belt from New Delhi to Kabul,and dry seasonal precipitation around the Kabul region increase significantly.Under different greenhouse gas emission scenarios,the areal averaged annual mean temperature is projected significant increase trend during 21 century,and the warming rate is significantly faster than the global.The precipitation shows a weak fluctuation upward trend,but has a large inter annual amplitude.Spatially,the basin is warming significantly,especially in the western,northwest and northern high-altitude mountain areas of the basin.Precipitation in the northern part of the mountainous area,the central and eastern regions is more significant with the increase of emission scenarios.(2)The basin had the most frequent of EPEs in July and August,with the longest duration and the most widespread impact area.Although the average annual frequency of EPE decreased slightly in the long-term trend,the impact area and duration of the single EPE in the past year all fluctuated.With the global warming,EPE with longer duration and larger impact area will be frequently affected in the future.The central and eastern parts of the basin will be more and more frequently affected by EPEs.(3)According to the ensemble mean of multi-GCMs,population exposure will increase by 73.8% and 124.6%72.4% and 122.7%,respectively,at 1.5°C and 2.0°C warming levels,with relative to reference period(1986-2005).The demographic change is responsible more to the tremendous increment of population exposure in the IRB.If population was held constant to level of 2010,increase of population exposure will be 7.2%,11.2%,respectively,at 1.5°C and 2°C warming levels.Limiting the increase of temperature to 1.5°C can substantially reduce population exposure to EPEs as compared to extra warmings,especially in the central and southwestern IRB.