Spatiotemporal Evaluation and Future Projection of Diurnal Temperature Range over the Tibetan Plateau in CMIP6 Models

The diurnal temperature range(DTR) serves as a vital indicator reflecting both natural climate variability and anthropogenic climate change. This study investigates the historical and projected multitemporal DTR variations over the Tibetan Plateau. It assesses 23 climate models from phase 6 of the Coupled Model Intercomparison Project(CMIP6) using CN05.1 observational data as validation, evaluating their ability to simulate DTR over the Tibetan Plateau. Then, the evolution of DTR over the Tibetan Plateau under different shared socioeconomic pathway(SSP) scenarios for the near,middle, and long term of future projection are analyzed using 11 selected robustly performing models. Key findings reveal:(1) Among the models examined, BCC-CSM2-MR, EC-Earth3, EC-Earth3-CC, EC-Earth3-Veg, EC-Earth3-Veg-LR,FGOALS-g3, FIO-ESM-2-0, GFDL-ESM4, MPI-ESM1-2-HR, MPI-ESM1-2-LR, and INM-CM5-0 exhibit superior integrated simulation capability for capturing the spatiotemporal variability of DTR over the Tibetan Plateau.(2) Projection indicates a slightly increasing trend in DTR on the Tibetan Plateau in the SSP1-2.6 scenario, and decreasing trends in the SSP2-4.5, SSP3-7.0, and SPP5-8.5 scenarios. In certain areas, such as the southeastern edge of the Tibetan Plateau, western hinterland of the Tibetan Plateau, southern Kunlun, and the Qaidam basins, the changes in DTR are relatively large.(3) Notably, the warming rate of maximum temperature under SSP2-4.5, SSP3-7.0, and SPP5-8.5 is slower compared to that of minimum temperature, and it emerges as the primary contributor to the projected decrease in DTR over the Tibetan Plateau in the future.

Surface air temperature changes over the Tibetan Plateau:Historical evaluation and future projection based on CMIP6 models

With its amplification simultaneously emerging in cryospheric regions,especially in the Tibetan Plateau,global warming is undoubtedly occurring.In this study,we utilized 28 global climate models to assess model performance regarding surface air temperature over the Tibetan Plateau from 1961 to 2014,reported spatiotemporal variability in surface air temperature in the future under four scenarios(SSP1-2.6,SSP2-4.5,SSP3-7.0,and SSP5-8.5),and further quantified the timing of warming levels(1.5,2,and 3℃)in the region.The results show that the multimodel ensemble means depicted the spatiotemporal patterns of surface air temperature for the past decades well,although with differences across individual models.The projected surface air temperature,by 2099,would warm by 1.9,3.2,5.2,and 6.3℃relative to the reference period(1981–2010),with increasing rates of 0.11,0.31,0.53,and 0.70℃/decade under the SSP1-2.6,SSP2-4.5,SSP3-7.0,and SSP5-8.5 scenarios for the period 2015–2099,respectively.Compared with the preindustrial periods(1850–1900),the mean annual surface air temperature over the Tibetan Plateau has hit the 1.5℃threshold and will break 2℃in the next decade,but there is still a chance to limit the temperature below 3℃in this century.Our study provides a new understanding of climate warming in high mountain areas and implies the urgent need to achieve carbon neutrality.

Evaluation of Natural Gas Supply Security in Turkey with Future Projection

Natural gas is one of the key energy resources for Turkey due to fact that 32% of annual primary energy supply and 45% of annual electricity production is obtained from natural gas with also common usage of residential and industrial zones. In this study, the supply security of natural gas was taken into consideration with strategic criteria of energy policy with the SWOT （strengths, weaknesses, opportunities and threats） analysis and the future projection for Turkey. It has been concluded on geopolitics criteria, domestic production and research for resources must be stimulated as high as possible and participation to abroad resources must be implemented.

Historical Changes and Future Projections of Extreme Temperature and Precipitation along the Sichuan-Tibet Railway

Based on multiresource high-resolution in situ and satellite merged observations along with model simulations from the Coordinated Regional Climate Downscaling Experiment(CORDEX),this study first investigated historical changes in extreme temperature and precipitation during the period of 1979-2018 in areas along the Sichuan-Tibet Railway,and then projected the future changes in the frequency and intensity of extreme temperature and precipitation under the RCP(Representative Concentration Pathway)4.5 and 8.5 scenarios.This paper is expected to enhance our understanding of the spatiotemporal variability in the extreme temperature and precipitation along the Sichuan-Tibet Railway,and to provide scientific basis to advance the Sichuan-Tibet Railway construction and operation.The results show that temperatures in the Sichuan-Tibet region display a noticeable warming trend in the past 40 years,and the increase of minimum temperature is significantly higher than that of maximum temperature in the northwest of the region.Significant increase of precipitation is found mainly over the northwest of the Tibetan Plateau.Except for Lhasa and its surrounding areas,precipitation over other areas along the Sichuan-Tibet Railway shows no significant change in the past 40 years,as indicated in five datasets;however,precipitation along the railway has shown a remarkable decrease in the past 20 years in the TRMM satellite dataset.The warm days and nights have clearly increased by 6 and 5 day decade1-for 1979-2019,while cold days and nights have markedly decreased by about 6.6 and 3.6 day decade-1,respectively.In the past 20 years,the areas with increased precipitation from very wet days and extremely wet days are mainly distributed to the north of the Sichuan-Tibet Railway,while in the areas along the railway itself,the very wet days and extremely wet days are decreasing.Under RCPs 4.5 and 8.5,the temperature in the Sichuan-Tibet region will increase significantly,and the frequency of extreme high(low)temperature events in the late 21 st century(2070-2099)will greatly increase(decrease)by about 50%-80%(10%)compared with occurrences in the late 20 th century(1970-1999).Meanwhile,the frequency of very wet days and extremely wet days in the Sichuan-Tibet region will increase by about 2%-19% and 2%-5%,respectively,and the areas along the Sichuan-Tibet Railway will be affected by more extreme high temperature and extreme precipitation events.

Evaluation and projection of marine heatwaves in the South China Sea: insights from CMIP6 multi-model ensemble

This study evaluates the performance of 16 models sourced from the coupled model intercomparison project phase 6(CMIP6)in simulating marine heatwaves(MHWs)in the South China Sea(SCS)during the historical period(1982−2014),and also investigates future changes in SCS MHWs based on simulations from three shared socioeconomic pathway(SSP)scenarios(SSP126,SSP245,and SSP585)using CMIP6 models.Results demonstrate that the CMIP6 models perform well in simulating the spatial-temporal distribution and intensity of SCS MHWs,with their multi-model ensemble(MME)results showing the best performance.The reasonable agreement between the observations and CMIP6 MME reveals that the increasing trends of SCS MHWs are attributed to the warming sea surface temperature trend.Under various SSP scenarios,the year 2040 emerges as pivotal juncture for future shifts in SCS MHWs,marked by distinct variations in changing rate and amplitudes.This is characterized by an accelerated decrease in MHWs frequency and a notably heightened increase in mean intensity,duration,and total days after 2040.Furthermore,the projection results for SCS MHWs suggest that the spatial pattern of MHWs remains consistent across future periods.However,the intensity shows higher consistency only during the near-term period(2021−2050),while notable inconsistencies are observed during the medium-term(2041−2070)and long-term(2071−2100)periods under the three SSP scenarios.During the nearterm period,the SCS MHWs are characterized by moderate and strong events with high frequencies and relatively shorter durations.In contrast,during the medium-term period,MHWs are also characterized by moderate and strong events,but with longer-lasting and more intense events under the SSP245 and SSP585 scenarios.However,in the long-term period,extreme MHWs become the dominant feature under the SSP585 scenario,indicating a substantial intensification of SCS MHWs,effectively establishing a near-permanent state.

Climate change and Aedes albopictus risks in China:current impact and future projection

Background Future distribution of dengue risk is usually predicted based on predicted climate changes using general circulation models(GCMs).However,it is difficult to validate the GCM results and assess the uncertainty of the predictions.The observed changes in climate may be very different from the GCM results.We aim to utilize trends in observed climate dynamics to predict future risks of Aedes albopictus in China.Methods We collected Ae.albopictus surveillance data and observed climate records from 80 meteorological stations from 1970 to 2021.We analyzed the trends in climate change in China and made predictions on future climate for the years 2050 and 2080 based on trend analyses.We analyzed the relationship between climatic variables and the prevalence of Ae.albopictus in different months/seasons.We built a classification tree model(based on the average of 999 runs of classification and regression tree analyses)to predict the monthly/seasonal Ae.albopictus distribution based on the average climate from 1970 to 2000 and assessed the contributions of different climatic variables to the Ae.albopictus distribution.Using these models,we projected the future distributions of Ae.albopictus for 2050 and 2080.Results The study included Ae.albopictus surveillance from 259 sites in China found that winter to early spring(November–February)temperatures were strongly correlated with Ae.albopictus prevalence(prediction accuracy ranges 93.0–98.8%)—the higher the temperature the higher the prevalence,while precipitation in summer(June–September)was important predictor for Ae.albopictus prevalence.The machine learning tree models predicted the current prevalence of Ae.albopictus with high levels of agreement(accuracy>90%and Kappa agreement>80%for all 12 months).Overall,winter temperature contributed the most to Ae.albopictus distribution,followed by summer precipitation.An increase in temperature was observed from 1970 to 2021 in most places in China,and annual change rates varied substantially from-0.22℃/year to 0.58℃/year among sites,with the largest increase in temperature occurring from February to April(an annual increase of 1.4–4.7℃ in monthly mean,0.6–4.0℃ in monthly minimum,and 1.3–4.3℃ in monthly maximum temperature)and the smallest in November and December.Temperature increases were lower in the tropics/subtropics(1.5–2.3℃ from February–April)compared to the high-latitude areas(2.6–4.6℃ from February–April).The projected temperatures in 2050 and 2080 by this study were approximately 1–1.5℃ higher than those projected by GCMs.The estimated current Ae.albopictus risk distribution had a northern boundary of north-central China and the southern edge of northeastern China,with a risk period of June–September.The projected future Ae.albopictus risks in 2050 and 2080 cover nearly all of China,with an expanded risk period of April–October.The current at-risk population was estimated to be 960 million and the future at-risk population was projected to be 1.2 billion.Conclusions The magnitude of climate change in China is likely to surpass GCM predictions.Future dengue risks will expand to cover nearly all of China if current climate trends continue.

Future Changes in the Relationship Between the South and East Asian Summer Monsoons in CMIP6 Models

The future changes in the relationship between the South Asian summer monsoon(SASM)and the East Asian summer monsoon(EASM)are investigated by using the high-emissions Shared Socioeconomic Pathway 5-8.5(SSP5-8.5)experiments from 26 coupled models that participated in the phase 6 of the Coupled Model Intercomparison Project(CMIP6).Six models,selected based on their best performance in simulating the upper-and lower-level pathways related to the SASM-EASM teleconnection in the historical run,can capture the positive relationship between the SASM and the rainfall over northern China.In the future scenario,the upper-level teleconnection wave pattern connecting the SASM and the EASM exhibits a significant weakening trend,due to the rainfall anomalies decrease over the northern Indian Peninsula in the future.At the lower level,the western North Pacific anticyclone is projected to strengthen in the warming climate.The positive(negative)rainfall anomalies associated with positive(negative)SASM rainfall anomalies are anticipated to extend southward from northern China to the Yangtze-Huai River valley,the Korea Peninsula,and southern Japan.The connection in the lower-level pathway may be strengthened in the future.

Climate Change Projections for Mediterranean Region with Focus over Alpine Region and Italy

Climate change projections over the Mediterranean region have been elaborated by using the outputs of ten ENSEMBLES regional climate simulations with an horizontal resolution of 25 km under the SRES A1B emission scenario. The analysis concerns some surface atmospheric variables： mean sea level pressure, temperature, precipitation and wind speed. At first, model validations have been performed by comparing model results with E-OBS and ERA-Interim data in reproducing the last decades over some Italian sub-areas and the Alpine region. In spite of the considerable spread in the models＇ performances to represent the reference climate, a multi-model reconstruction has been computed and some seasonal climate change projections have been elaborated. About the mean climate changes, the more significant signals expected by 2050 are a maximum warming （about 2 ~C） and maximum drying （about 20%） in the southern Europe in summer. Moreover, the results indicate an increasing risk for some severe weather conditions： more days of extremely high temperature in summer over the whole area, a greater occurrence of flooding and storms over coasts during spring and autumn seasons and a more serious wet-snow event over Alpine region in winter. No significant signals of wind changes have been detected.

The Hope Project:the Future Has a Price

The Hope Project has made a difference to the lives of many chldren in China..This magazine has also received a large number of inquiries from overseas readers.and,to answer their questions,we bring more informa-tion on the Hope Project in the following outline.Readers can contact the Hope Project directly,and China I oday will also be happy to answer reader inquiries.

Water Vapor Transport and Cross-Equatorial Flow over the Asian-Australia Monsoon Region Simulated by CMIP5 Climate Models

The summer mean water vapor transport （WVT） and cross-equatorial flow （CEF） over the Asian- Australian monsoon region simulated by 22 coupled atmospheric-oceanic general circulation models （AOGCMs） from the World Climate Research Programme＇s Coupled Model Intercomparison Project Phase 5 （CMIP5） were evaluated. Based on climatology of the twentieth-century simulations, most of models have a reason- ably realistic representation of summer monsoon WVT characterized by southeast water vapor conveyor belt over the South Indian Ocean and southwest belt from the Arabian Sea to the East Asian. The correlation coefficients between NCEP reanalysis and simulations of BCC-CSMI-1, BNU-ESM, CanESM2, FGOALS-s2, MIROC4h and MPI-ESM-LR are up to 0.8. The simulated CEF depicted by the meridional wind along the equator includes the Somali jet and eastern CEF in low atmosphere and the reverse circulation in upper atmosphere, which were generally consistent with NCEP reanalysis. Multi-model ensemble means （MME） can reproduce more reasonable climatological features in spatial distribution both of WVT and CEF. Ten models with more reasonable WVT simulations were selected for future projection studies, including BCC- CSMI-1, BNU-ESM, CanESM2, CCSM4, FGOALS-s2, FIO-ESM, GFDL-ESM2G, MRIOCS, MPI-ESM-LR and NorESM-1M. Analysis based on the future projection experiments in RCP （Representative Concentra- tion Pathway） 2.6, RCP4.5, RCP6 and RCP8.5 show that the global warming forced by different RCP scenarios will results in enhanced WVT over the Indian area and the west Pacific and weaken WVT in the low latitudes of tropical Indian Ocean.

How Frequently Will the Persistent Heavy Rainfall over the Middle and Lower Yangtze River Basin in Summer 2020 Happen under Global Warming?

The middle and lower Yangtze River basin(MLYRB)suffered persistent heavy rainfall in summer 2020,with nearly continuous rainfall for about six consecutive weeks.How the likelihood of persistent heavy rainfall resembling that which occurred over the MLYRB in summer 2020(hereafter 2020PHR-like event)would change under global warming is investigated.An index that reflects maximum accumulated precipitation during a consecutive five-week period in summer(Rx35day)is introduced.This accumulated precipitation index in summer 2020 is 60%stronger than the climatology,and a statistical analysis further shows that the 2020 event is a 1-in-70-year event.The model projection results derived from the 50-member ensemble of CanESM2 and the multimodel ensemble(MME)of the CMIP5 and CMIP6 models show that the occurrence probability of the 2020PHR-like event will dramatically increase under global warming.Based on the Kolmogorov-Smirnoff test,one-third of the CMIP5 and CMIP6 models that have reasonable performance in reproducing the 2020PHR-like event in their historical simulations are selected for the future projection study.The CMIP5 and CMIP6 MME results show that the occurrence probability of the 2020PHR-like event under the present-day climate will be double under lower-emission scenarios(CMIP5 RCP4.5,CMIP6 SSP1-2.6,and SSP2-4.5)and 3-5 times greater under higher-emission scenarios(3.0 times for CMIP5 RCP8.5,2.9 times for CMIP6 SSP3-7.0,and 4.8 times for CMIP6 SSP5-8.5).The inter-model spread of the probability change is small,lending confidence to the projection results.The results provide a scientific reference for mitigation of and adaptation to future climate change.

Nuclear Energy in the Energy Expansion of Turkey

Dependency of the human on the energy is ever-increasing today and the energy policies are reaching undeniable and un-ignorable dimensions steering the political events as well. Therefore, access to the energy and/or energy resources is becoming the highest priority for the countries. In this study, the criteria that have to be kept in view while creating the energy policies are explained first of all. Then the geopolitics, redundancy and diversity are described as the strategic criteria and furthermore, the availability, energy resources geography, and the technological, economical and environmental criteria are examined as the operative criteria and thereafter the issues such as installation period, utilization period, reliability, repair-maintenance and public validation are handled as the tactical criteria. The nuclear power plants are examined and evaluated according to the criteria set forth above while creating the energy policies. Under the light of this evaluation, the situation is examined and explicated in terms of the energy expansion of Turkey. Thus the place of the nuclear energy in the energy expansion of Turkey is clarified and emphasized.

Snow algal blooms in Antarctic King George Island in 2017-2022 and their future trend based on CMIP6 projection

Snow algal blooms have a remarkable climatic or environmental effect through influencing the snow-albedo feedback,accelerating the melting of surface snow,and amplifying global warming.Snow algal blooms occurred frequently on King George Island,Antarctic,during the recent six austral summers(December to next February)through 2017-2022.Based on an assessment of satellite images,this study found that the range and amount of snow algal blooms in the summers of 2018,2020,2021 and 2022 are relatively larger than in the summers of 2017 and 2019.Whether meteorological conditions have shaped the year-to-year variation of algal bloom intensities is analyzed through observational composite.The results suggest that during the strong bloom summers there exist prevailing northerly or northwesterly wind anomalies which advect warm and humid airmass from the southern ocean into the island,increasing surface air temperature and humidity;the warmer and more humid surface favors melting of snow and an increase of low cloud cover,subsequently enhancing the atmospheric downward long-wave radiation and amplifying surface warmth;the increased low cloud cover reflects more ultraviolet rays back to space and weakens the short-wave radiation reaching the surface.All these factors together favor to a stronger bloom.In comparison,during 2017 and 2019 there exist weak southerly wind anomalies which induce the northward advection of cold and dry air from the Antarctic Continent and favor the cooler surface.Consequently,it is unfavorable for the snow algal bloom.Based on these results,a snow algal bloom potential index(API)integrating the meteorological conditions is constructed,and its future trend is projected based on the EC-Earth3 run attending the CMIP6 under SSP245 and SSP585.A significant increasing trend is projected especially under SSP585.Thus snow algal bloom on King George Island will become more frequent and stronger in future.This implies a potential accelerate melting of ice shelf over Antarctic Peninsula.

Statistical Downscaling of Summer Temperature Extremes in Northern China

Two approaches of statistical downscaling were applied to indices of temperature extremes based on percentiles of daily maximum and minimum temperature observations at Beijing station in summer during 1960-2008. One was to downscale daily maximum and minimum temperatures by using EOF analysis and stepwise linear regression at first, then to calculate the indices of extremes; the other was to directly downseale the percentile-based indices by using seasonal large-scale temperature and geo-potential height records. The cross-validation results showed that the latter approach has a better performance than the former. Then, the latter approach was applied to 48 meteorological stations in northern China. The cross- validation results for all 48 stations showed close correlation between the percentile-based indices and the seasonal large-scale variables. Finally, future scenarios of indices of temperature extremes in northern China were projected by applying the statistical downsealing to Hadley Centre Coupled Model Version 3 （HadCM3） simulations under the Representative Concentration Pathways 4.5 （RCP 4.5） scenario of the Fifth Coupled Model Inter-comparison Project （CMIP5）. The results showed that the 90th percentile of daily maximum temperatures will increase by about 1.5℃, and the 10th of daily minimum temperatures will increase by about 2℃ during the period 2011- 35 relative to 1980-99.

Multi-Model Ensemble Projection of Precipitation Changes over China under Global Warming of 1.5 and 2℃ with Consideration of Model Performance and Independence

A weighting scheme jointly considering model performance and independence(PI-based weighting scheme) is employed to deal with multi-model ensemble prediction of precipitation over China from 17 global climate models. Four precipitation metrics on mean and extremes are used to evaluate the model performance and independence. The PIbased scheme is also compared with a rank-based weighting scheme and the simple arithmetic mean(AM) scheme. It is shown that the PI-based scheme achieves notable improvements in western China, with biases decreasing for all parameters. However, improvements are small and almost insignificant in eastern China. After calibration and validation, the scheme is used for future precipitation projection under the 1.5 and 2℃ global warming targets(above preindustrial level). There is a general tendency to wetness for most regions in China, especially in terms of extreme precipitation. The PI scheme shows larger inhomogeneity in spatial distribution. For the total precipitation PRCPTOT(95 th percentile extreme precipitation R95 P), the land fraction for a change larger than 10%(20%) is 22.8%(53.4%)in PI, while 13.3%(36.8%) in AM, under 2℃ global warming. Most noticeable increase exists in central and east parts of western China.

Future changes in wind energy potential over China using RegCM4 under RCP emission scenarios

To provide a scientific basis for the policies for the development of wind energy and towards the goal of carbon neutrality in China and local governments,changes in wind energy potential over China were investigated based on the bias-corrected ensemble mean(CENS)of high-resolution dynamical downscaling projections using the RCP2.6,RCP4.5 and RCP8.5 emission scenarios.Firstly,evaluation indicated that CENS could better reproduce the long-term mean and interannual variability of surface wind speed over China compared to the original simulation outputs,providing a reliable basis for future projections.Projection of the averaged wind power density of China showed a decreasing trend during 2020-2099 in all four seasons under all three scenarios,with the significant(p<0.05)magnitude apparent in both autumn and winter,characterized by an increase over South China and a decrease over northwestern and southwestern regions.In addition,the'very abundant'and'abundant'categories of available wind energy located in northern China and the low-speed wind energy in South China were projected to decrease by the middle and late of the 21st century.Although the projected decrease in annual wind power density ranged from-1.14%to-0.36%per decade among the three scenarios,we believe that,considering the strong inter-annual variability and uncertainty involved,these changes would not substantially affect China's future wind energy plans.Also of note was that a low emission scenario could to some extent mitigate the reduction in wind energy potential in the future.Furthermore,we suggest that implementation of newly developed wind power technology should consider the impact of changes in wind energy in different sub-regions(e.g.,the low wind speed region over South China),which is pivotal to China's strategic planning in this sector.

Deep learning projects future warming-induced vegetation growth changes under SSP scenarios

Climate warming has been projected to enhance vegetation growth more strongly in higher latitudes than in lower latitudes,but different projections show distinct regional differences.By employing big data analysis(deep learning),we established gridded,global-scale,climate-driven vegetation growth models to project future changes in vegetation growth under SSP scenarios.We projected no substantial trends of vegetation growth change under the sustainable development scenario(SSP1-1.9)by the end of the 21st century.However,the increase of vegetation growth driven by climate warming shows distinct regional variability under the scenario representing high carbon emissions and severe warming(SSP5-8.5),especially in Northeast Asia where growth could increase by(6.00%±4.21%).This may be attributed to the high temperature sensitivities of the deciduous needleleaf forests and permanent wetlands in these regions.When the temperature sensitivity that is defined as permutation importance in deep learning is greater than 0.05,the increase in vegetation growth will be more prominent.In addition,an extreme temperature increase across grasslands,as well as changing land-use management in northern China may also influence the vegetation growth in the future.The results suggest that the sustainable development scenario can maintain stable vegetation growth,and it may be a reliable way to mitigate global warming due to potential climate feedbacks driven by vegetation changes in boreal regions.Deciduous needleleaf forests will be a centre of greening in the future,and it should become the focus of future vegetation dynamics modelling studies and projections.

Diurnal asymmetry in future temperature changes over the main Belt and Road regions

Introduction:Daily maximum(Tmax)and minimum(Tmin)temperatures and Diurnal temperature range(DTR)profoundly affect the ecological environment and socioeconomic systems.In this study,we project future changes in Tmax,Tmin and DTR for RCP4.5 and RCP8.5 using fine-resolution downscaled data from the 18global coupled models over the main regions of the Belt and Road Initiative(BRI).Outcomes:The Multi-Model Ensemble(MME)mean projections show that future warming is stronger in Tmax than in Tmin,leading to the increased DTR over central and southern Europe,many areas surrounding the Black Sea and the Caspian Sea,and southeastern China.By contrast,the DTR is projected to decline over the regions north of 55°N and other some areas due to the more rapid increase in Tmin than in Tmax.As a whole,the diurnal asymmetry of projected future temperature changes is found to mainly occur from November to March.Conclusions:Our findings contribute to the knowledgebase on climate change over the main BRI regions.Regarding uneven spatiotemporal changes in Tmax,Tmin and DTR,appropriate climate change adaptation strategies,and options should be adopted to reduce or avoid disadvantaged consequences to the natural system and human society over specific regions.

Future Drought Changes in China Projected by the CMIP6 Models:Contributions from Key Factors

Model simulations show that drought may become more severe and widespread in the 21st century due to humaninduced global warming. However, the contributions from the key factors to the model-projected drought changes in China have not yet been examined in detail. We used the self-calibrated Palmer Drought Severity Index with Penman–Monteith potential evapotranspiration(scPDSIpm) based on 10 model simulations selected from the Coupled Model Intercomparison Project Phase 6(CMIP6). We investigated the contributions from precipitation(P), near-surface air temperature and specific humidity [Δ(T + q)], net surface longwave radiation(LW), net surface shortwave radiation(SW), and wind speed(WS) to the future changes in scPDSIpm, including the long-term mean, drying area,probability distribution function(PDF), drought frequency, and drought duration based on the scPDSIpm over China.Our results show that model-projected drying mainly occurs over southern China, whereas the dry areas under drought conditions increase from 20% to about 23%/30% under the two scenarios of the shared socioeconomic pathway(SSP2-4.5/SSP5-8.5) from 1985 to 2100, despite large uncertainties in individual projections partly due to internal variability. Drought frequency is projected to increases by about 10%–54%(15%–88%) under the SSP2-4.5(SSP5-8.5) scenario by the late 21st century, along with increases in drought duration. These changes are accompanied by a decrease in the mean scPDSIpm and flattening of the PDFs. The changes in drying over southern China are mainly attributed to surface warming and the increased surface vapor pressure deficit(VPD), with small contributions from changes in the surface net radiation. The changes in wetting over northern China mostly result from increased precipitation along with a small wetting effect from the changes in wind speed.

Role of adaptation measures in addressing heatwave exposure in China

Heatwave exposure has increased dramatically because of climate warming and population growth,along with their interactive effects.However,effective adaptation measures can reduce these impacts.Nonetheless,the dynamic changes,regional inequality in adaptive capacity and their potential contributions to reducing exposure in the future remain unclear.This study quantifies the impact of adaptive capacity and underscores regional variations in heatwave magnitudes,population exposure and adaptation levels in China.We projected the future adaptive capacity using air-conditioner penetration,factoring in climate cooling requirements and individuals'purchasing power.Utilising population and gross domestic product(GDP)data from four Shared Socioeconomic Pathways(SSP1,SSP2,SSP3 and SSP5)and daily temperature data from four SSP-based emission scenarios(SSP1-2.6,SSP2-4.5,SSP3-7.0 and SSP5-8.5),we estimated heatwave duration,population exposure and avoided impacts through adaptation across China and its sub-regions.Results show a substantial increase in heatwave duration in Southwest and Southern China,especially under the SSP5-8.5 scenario,with a projection of 163.2±36.7 d during 2081-2100.Under the SSP3|SSP3-7.0 scenario,total exposure reaches 156.4±76.8 billion person d per year,which is the highest among all scenarios and 23 times greater than that in 1986-2005 without adaptation.Upon considering adaptation measures,a noteworthy reduction in population exposure is observed,especially in the SSP3|SSP3-7.0 and SSP5JSSP5-8.5 scenarios,with reductions of(62.6±3.9)%and(65.8±5.1)%,respectively,compared with the scenario without adaptation during 2081-2100.Remarkable regional disparities in avoided impacts are also evident,with variations of up to 50%across different regions.The implementation of effective and environmentally friendly adaptation measures can notably address climate change,thereby alleviating the profound threats posed to human well-being.