Dramatic Increase In Future Population Exposure To High-Temperature And Their Related Health Risks In China

With the continued warming,the frequency,intensity,and duration of high temperature are expected to increase dramatically,which could result in alarming hospitalizations and excess deaths worldwide.As one of the countries most affected by high temperature,how will China’s high temperatures be characterized? How will population exposure to high temperature change in the future? What role do climate and population play in changing population exposures? Which regions of China will have the highest future health risks of population exposure? Findings from this study are expected to provide a certain scientific basis and important information for assessing the health risks of future climate change.In this paper,based on the results of temperature and relative humidity simulations under the SSP2-4.5 and SSP5-8.5 scenarios of the Coupled Model Intercomparison Project Phase 6(CMIP6),we adopted a heat stress index(Wet Bulb Globe Temperature,WBGT)to estimate the future population exposure to high temperature in China and analyze the factors influencing the exposure changes.And then we assessed the relationship between population exposure to high temperature and the number of deaths in China to explore the health risks of population exposure in the 21 st century.Main findings are as follows:(1)Compared to the reference period,the substantial increase in the number of days,intensity and maximum duration of high-temperature are projected with time and emission scenario rising.In most regions,the number of days,intensity and maximum duration of T90-95p(WBGT is in the range of(90th,95th])and T95-99p(WBGT is in the range of(95th,99th])decrease slightly,while >T99p(WBGT > the 99 th percentile derived from the reference period)upsurges significantly.Spatially,the variation in the number of high temperature days and maximum duration compared to the reference period generally decreases from south to north,with the greatest change in the southwest and south,followed by the east,central and northwest,and the least change in the northeast and north.(2)Population exposure to high temperature is projected to increase significantly in the future,with a larger increase under the SSP5-8.5 scenario than that under the SSP2-4.5 scenario.Compared with the reference period(43.735 billion person-days),the total exposure to high temperature increases to 1.92(2.01)times in the near-term and 2.16(2.35)times in the long-term under the SSP2-4.5 scenario(the SSP5-8.5 scenario),respectively.The exposure of T90-95 p and T95-99 p in China tends to decrease in the future,and the exposure to >T99p is expected to upsurge extremely.The south,east and central confront the greatest changes,whereas the northwest,north and northeast are projected to present relatively small variation.The population effect is absolutely dominant in influencing the changes in exposure to T90-95 p and T95-99 p,and the climate effect is the most prominent contributor to the changes in exposure to >T99p in most areas.(3)The effect of population exposure on deaths is significant.An additional 0.1billion person-days increase in population exposure to T90-95 p,T95-99 p and >T99p in a given year increased the number of deaths by 1002(95% CI: 570～1434),2926(95%CI: 1783～4069)and 2635(95% CI: 1345～3925),respectively.The relationships between population exposure to high temperature and deaths are robust.(4)Future population exposure-related health risks are projected to increase significantly,with the increase being greater under higher emission scenarios and stronger heat.Under the SSP2-4.5 scenario(the SSP5-8.5 scenario),compared with the reference period,the total exposure to high temperature-related deaths will increase by1.2266(95% CI: 0.6341～1.8192)[1.3575(95% CI: 0.6926～2.0223)] million in the near-term and 1.5885(95% CI: 0.7869～2.3902)[1.8901(95% CI: 0.9230～2.8572)]million in the long-term,and the related mortality will increase by 0.86‰(95% CI:0.45～1.28‰)[0.99‰(95% CI: 0.50～1.47‰)] and 1.25‰(95% CI: 0.62～1.89‰)[1.85‰(95% CI: 0.90～2.79‰)],respectively.Spatial patterns of the increase in related deaths are consistent with that of population exposure.In summary,our results emphasize that regional extreme high temperatures and their population exposure will increase substantially with global warming,which should be taken seriously.These changes are mainly caused by the increase in extreme heat.Climate change,the main cause of increased population exposure,should be strengthened in the process of future population exposure prevention.In addition,the results demonstrate that the population is exposed to greater health risks at higher temperatures,especially in the south,east and central.These regions should enhance their emission reduction efforts in a targeted manner to improve the risk management according to different levels of health risk.