“I call on all leaders worldwide to declare a State of Climate Emergency in their own countries until carbon neutrality is reached.”–António GUTERRES(United Nations Secretary General),12 December,2020 There is...“I call on all leaders worldwide to declare a State of Climate Emergency in their own countries until carbon neutrality is reached.”–António GUTERRES(United Nations Secretary General),12 December,2020 There is no shortcut to a carbon neutral society;solutions are urgently required from both energy&industrial sectors and global ecosystems.While the former is often held accountable and emphasized in terms of its emissions reduction capability,the latter(recently termed natural climate solutions)should also be assessed for potential and limitations by the scientific community,the public,and policy makers.展开更多
The carbon cycle is one of the fundamental climate change issues.Its long-term evolution largely affects the amplitude and trend of human-induced climate change,as well as the formulation and implementation of emissio...The carbon cycle is one of the fundamental climate change issues.Its long-term evolution largely affects the amplitude and trend of human-induced climate change,as well as the formulation and implementation of emission reduction policy and technology for stabilizing the atmospheric CO2concentration.Two earth system models incorporating the global carbon cycle,the Community Earth System Model and the Beijing Normal University-Earth System Model,were used to investigate the effect of the carbon cycle on the attribution of the historical responsibility for climate change.The simulations show that when compared with the criterion based on cumulative emissions,the developed(developing)countries’responsibility is reduced(increased)by 6%–10%using atmospheric CO2concentration as the criterion.This discrepancy is attributed to the fact that the developed world contributed approximately61%–68%(61%–64%)to the change in global oceanic(terrestrial)carbon sequestration for the period from 1850 to2005,whereas the developing world contributed approximately 32%–49%(36%–39%).Under a developed world emissions scenario,the relatively larger uptake of global carbon sinks reduced the developed countries’responsibility for carbon emissions but increased their responsibility for global ocean acidification(68%).In addition,the large emissions from the developed world reduced the efficiency of the global carbon sinks,which may affect the long-term carbon sequestration and exacerbate global warming in the future.Therefore,it is necessary to further consider the interaction between carbon emissions and the carbon cycle when formulating emission reduction policy.展开更多
Recently,five Global LAnd Surface Satellite(GLASS)products have been released:leaf area index(LAI),shortwave broadband albedo,longwave broadband emissivity,incident short radiation,and photosynthetically active radiat...Recently,five Global LAnd Surface Satellite(GLASS)products have been released:leaf area index(LAI),shortwave broadband albedo,longwave broadband emissivity,incident short radiation,and photosynthetically active radiation(PAR).The first three products cover the years 19822012(LAI)and 19812010(albedo and emissivity)at 15 km and 8-day resolutions,and the last two radiation products span the period 20082010 at 5 km and 3-h resolutions.These products have been evaluated and validated,and the preliminary results indicate that they are of higher quality and accuracy than the existing products.In particular,the first three products have much longer time series,and are therefore highly suitable for various environmental studies.This paper outlines the algorithms,product characteristics,preliminary validation results,potential applications and some examples of initial analysis of these products.展开更多
Background:Although soil erosion plays a key role in the carbon cycle,a holistic and mechanistic understanding of the soil erosion process within the cycle is still lacking.The aim of this study was therefore to impro...Background:Although soil erosion plays a key role in the carbon cycle,a holistic and mechanistic understanding of the soil erosion process within the cycle is still lacking.The aim of this study was therefore to improve our mechanistic understanding of soil organic carbon(SOC)and soil respiration dynamics through an experiment conducted in an eroding black soil farmland landscape in Northeast China.Results:The depositional profiles store 5.9 times more SOC than the eroding profiles and 3.3 times more SOC than the non-eroding profiles.A linear correlation between the SOC and 137Cs(Caesium-137)was observed in our study,suggesting that the SOC decreased with increased soil erosion.Furthermore,the fractions of intermediate C and the microaggregate C were lowest at the eroding position and highest at the depositional position.In the depositional topsoil,the input of labile materials plays a promotional role in soil respiration.Conversely,in the subsoil(i.e.,below 10 cm),the potential mineralization rates were lowest at the depositional position—due to effective stabilization by physical protection within soil microaggregates.The field results of soil surface respiration also suggest that the depositional topsoil SOC is prone to be mineralized and that SOC at this depositional context is stabilized at subsoil depth.In addition,the high water contents at the depositional position can limit the decomposition rates and stabilize the SOC at the same time.Conclusions:The findings from this study support that a majority of the SOC at footslope is stored within most of the soil profile(i.e.,below 10 cm)and submitted to long-term stabilization,and meanwhile support that the depositional profile emits more CO2 than the summit due to its high amount and quality of SOC.展开更多
China’s high ambitions to reach peak CO_(2) emissions by 2030 and carbon neutrality by 2060 make carbon mitigation an urgent issue with widespread societal consequences.To develop an achievable roadmap and an effecti...China’s high ambitions to reach peak CO_(2) emissions by 2030 and carbon neutrality by 2060 make carbon mitigation an urgent issue with widespread societal consequences.To develop an achievable roadmap and an effective portfolio of climate policies,it is essential that a clear picture of the magnitude and uncertainty of China’s current carbon balance is available,at both national and regional levels.展开更多
In this study, we explore the feasibility of optimizing ecosystem photosynthetic and respiratory parameters from the seasonal variation of the net carbon flux. An optimization scheme is proposed to estimate two key pa...In this study, we explore the feasibility of optimizing ecosystem photosynthetic and respiratory parameters from the seasonal variation of the net carbon flux. An optimization scheme is proposed to estimate two key parameters(Vmax25and Q10) by exploiting the seasonal variation in the net ecosystem carbon flux retrieved by an atmospheric inversion system. This scheme is implemented to estimate Vmax25 and Q10of the boreal ecosystem productivity simulator(BEPS) to improve its NEP simulation in the boreal North American region. Then, in situ NEE observations at six eddy covariance sites are used to evaluate the NEE simulations from BEPS with initial and optimized parameters. The results show that the performance of the optimized BEPS is superior to that of the BEPS with the default parameter values. These results implicate that it is possible to optimize ecosystem model parameters by different sensitivities of Vmax25 and Q10during growing and non-growing seasons through atmospheric inversion or data assimilation techniques.展开更多
Vegetation gross primary production(GPP)is an important variable for the carbon cycle on the Qinghai-Tibetan Plateau(QTP).Based on the measurements from 12 eddy covariance flux sites,we validated a light use efficienc...Vegetation gross primary production(GPP)is an important variable for the carbon cycle on the Qinghai-Tibetan Plateau(QTP).Based on the measurements from 12 eddy covariance flux sites,we validated a light use efficiency model(i.e.EC-LUE)to evaluate the spatial-temporal patterns of GPP and the effect of environmental variables on QTP.In general,EC-LUE model performed well in predicting GPP at different time scale over QTP.Annual GPP over the entire QTP ranged from 575 to 703 Tg C,and showed a significantly increasing trend from 1982 to 2013.However,there were large spatial heterogeneities in long-term trends of GPP.Throughout the entire QTP,air temperature increase had a greater influence than solar radiation and precipitation(PREC)changes on productivity.Moreover,our results highlight the large uncertainties of previous GPP estimates due to insufficient parameterization and validations.When compared with GPP estimates of the EC-LUE model,most Coupled Model Intercomparison Project(CMIP5)GPP products overestimate the magnitude and increasing trends of regional GPP,which potentially impact the feedback of ecosystems to regional climate changes.展开更多
PenmanMonteith(PM)theory has been successfully applied to calculate land surface evapotranspiration(ET)for regional and global scales.However,soil surface resistance,related to soil moisture,is always difficult to det...PenmanMonteith(PM)theory has been successfully applied to calculate land surface evapotranspiration(ET)for regional and global scales.However,soil surface resistance,related to soil moisture,is always difficult to determine over a large region,especially in arid or semiarid areas.In this study,we developed an ET estimation algorithm by incorporating soil moisture control,a soil moisture index(SMI)derived from the surface temperature and vegetation index space.We denoted this ET algorithm as the PM-SMI.The PM-SMI algorithm was compared with several other algorithms that calculated soil evaporation using relative humidity,and validated with Bowen ratio measurements at seven sites in the Southern Great Plain(SGP)that were covered by grassland and cropland with low vegetation cover,as well as at three eddy covariance sites from AmeriFlux covered by forest with high vegetation cover.The results show that in comparison with the other methods examined,the PM-SMI algorithm significantly improved the daily ET estimates at SGP sites with a root mean square error(RMSE)of 0.91 mm/d,bias of 0.33 mm/d,and R^(2) of 0.77.For three forest sites,the PM-SMI ET estimates are closer to the ET measurements during the non-growing season when compared with the other three algorithms.At all the 10 validation sites,the PMSMI algorithm performed the best.PM-SMI 8-day ET estimates were also compared with MODIS 8-day ET products(MOD16A2),and the latter showed negligible bias at SGP sites.In contrast,most of the PM-SMI 8-day ET estimates are around the 1:1 line.展开更多
Relationships among productivity,leaf phenology,and seasonal variation in moisture and light availability are poorly understood for evergreen broadleaved tropical/subtropical forests,which contribute 25% of terrestria...Relationships among productivity,leaf phenology,and seasonal variation in moisture and light availability are poorly understood for evergreen broadleaved tropical/subtropical forests,which contribute 25% of terrestrial productivity.On the one hand,as moisture availability declines,trees shed leaves to reduce transpiration and the risk of hydraulic failure.On the other hand,increases in light availability promote the replacement of senescent leaves to increase productivity.Here,we provide a comprehensive framework that relates the seasonality of climate,leaf abscission,and leaf productivity across the evergreen broadleaved tropical/subtropical forest biome.The seasonal correlation between rainfall and light availability varies from strongly negative to strongly positive across the tropics and maps onto the seasonal correlation between litterfall mass and productivity for 68 forests.Where rainfall and light covary positively,litterfall and productivity also covary positively and are always greater in the wetter sunnier season.Where rainfall and light covary negatively,litterfall and productivity are always greater in the drier and sunnier season if moisture supplies remain adequate;otherwise productivity is smaller in the drier sunnier season.This framework will improve the representation of tropical/subtropical forests in Earth system models and suggests how phenology and productivity will change as climate change alters the seasonality of cloud cover and rainfall across tropical/subtropical forests.展开更多
The Glasgow Declaration on Forests signed at the recent UN Climate Change Conference(COP 26)committed to halting forest loss by 2030.141 countries and regions,collectively covering over 90%of global forest,endorsed th...The Glasgow Declaration on Forests signed at the recent UN Climate Change Conference(COP 26)committed to halting forest loss by 2030.141 countries and regions,collectively covering over 90%of global forest,endorsed this declaration.Avoiding forest loss can generally contribute to climate change mitigation;however,the impacts of the declaration on global carbon dioxide(CO_(2))emission reduction are still unclear.Here we show that the Glasgow Declaration,if implemented fully and in a timely fashion,could reduce 123 Gt CO_(2) of emission from 2021 to 2050.This study also highlights that any delays in implementing the declaration would decrease the avoided emission.Although the Glasgow Declaration is a milestone for mitigating climate change,the more ambitious afforestation plan is urgently needed to keep the global temperature rise to below 1.5C relative to pre-industrial levels.展开更多
As the second largest producer of maize,China contributes 23%of global maize production and plays an important role in guaranteeing maize markets stability.In spite of its importance,there is no 30m spatial resolution...As the second largest producer of maize,China contributes 23%of global maize production and plays an important role in guaranteeing maize markets stability.In spite of its importance,there is no 30m spatial resolution distribution map of maize for all of China.This study used a time-weighted dynamic time warping method to identify planting areas of maize by comparing the similarity of time series of a satellite-based vegetation index at each pixel with a standard time series derived from known maize fields and mapped maize distribution from 2016 to 2020 over 22 provinces accounting for more than 99%of the maize planting area in China.Based on 18800 field-surveyed pixels at 30-meter spatial resolution,the distribution map yields 76.15%and 81.59%of producer’s and user’s accuracies averaged over the entire investigated provinces,respectively.Municipality-and county-level census data also show a good performance in reproducing the spatial distribution of maize.This study provides an approach to mapping maize over large areas based on a small volume of field survey data.展开更多
It has been long established that the terrestrial vegetation in spring has stronger photosynthetic capability than in autumn.However,this study challenges this consensus by comparing photosynthetic capability of terre...It has been long established that the terrestrial vegetation in spring has stronger photosynthetic capability than in autumn.However,this study challenges this consensus by comparing photosynthetic capability of terrestrial vegetation between the spring and autumn seasons based on measurements of 100 in situ eddy covariance towers over global extratropical ecosystems.At the majority of these sites,photosynthetic capability,indicated by light use efficiency(LUE)and apparent quantum efficiency,is significantly higher in autumn than in spring,due to lower atmosphere vapor pressure deficit(VPD)at the same air temperature.Seasonal VPD differences also substantially explain the interannual variability of the differences in photosynthetic capability between spring and autumn.We further reveal that VPD in autumn is significantly lower than in spring over 74.14% of extratropical areas,based on a global climate dataset.In contrast,LUE derived from a data-driven vegetation production dataset is significantly higher in autumn in over 61.02% of extratropical vegetated areas.Six Earth system models consistently projected continuous larger VPD values in spring compared with autumn,which implies that the impacts on vegetation growth will long exist and should be adequately considered when assessing the seasonal responses of terrestrial ecosystems to future climate conditions.展开更多
基金This work was jointly supported by the National Basic Research Program of China(2016YFA0602701)the National Natural Science Foundation of China(41975113)+1 种基金the Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies(2020B1212060025)the Guangdong Provincial Department of Science and Technology(2019ZT08G090)。
文摘“I call on all leaders worldwide to declare a State of Climate Emergency in their own countries until carbon neutrality is reached.”–António GUTERRES(United Nations Secretary General),12 December,2020 There is no shortcut to a carbon neutral society;solutions are urgently required from both energy&industrial sectors and global ecosystems.While the former is often held accountable and emphasized in terms of its emissions reduction capability,the latter(recently termed natural climate solutions)should also be assessed for potential and limitations by the scientific community,the public,and policy makers.
基金This work was supported by the International Research Center of Big Data for Sustainable Development Goals,the National Natural Science Foundation of China(42271422 and 41930648)the Open Fund of Key Laboratory of Urban Land Resources Monitoring and Simulation,Ministry of Natural Resources(KF-2020-05-025).
基金supported by the Fundamental Research Funds for the Central Universities(2012YBXS27)the National Key Program for Global Change Research of China(2010CB950500)
文摘The carbon cycle is one of the fundamental climate change issues.Its long-term evolution largely affects the amplitude and trend of human-induced climate change,as well as the formulation and implementation of emission reduction policy and technology for stabilizing the atmospheric CO2concentration.Two earth system models incorporating the global carbon cycle,the Community Earth System Model and the Beijing Normal University-Earth System Model,were used to investigate the effect of the carbon cycle on the attribution of the historical responsibility for climate change.The simulations show that when compared with the criterion based on cumulative emissions,the developed(developing)countries’responsibility is reduced(increased)by 6%–10%using atmospheric CO2concentration as the criterion.This discrepancy is attributed to the fact that the developed world contributed approximately61%–68%(61%–64%)to the change in global oceanic(terrestrial)carbon sequestration for the period from 1850 to2005,whereas the developing world contributed approximately 32%–49%(36%–39%).Under a developed world emissions scenario,the relatively larger uptake of global carbon sinks reduced the developed countries’responsibility for carbon emissions but increased their responsibility for global ocean acidification(68%).In addition,the large emissions from the developed world reduced the efficiency of the global carbon sinks,which may affect the long-term carbon sequestration and exacerbate global warming in the future.Therefore,it is necessary to further consider the interaction between carbon emissions and the carbon cycle when formulating emission reduction policy.
基金the‘Generation and Application of Global Products of Essential Land Variables’project funded and managed by the National Remote Sensing Center of China,Ministry of Science and Technology of China(2009AA122100)with the participation of about 20 universities and research institutes.
文摘Recently,five Global LAnd Surface Satellite(GLASS)products have been released:leaf area index(LAI),shortwave broadband albedo,longwave broadband emissivity,incident short radiation,and photosynthetically active radiation(PAR).The first three products cover the years 19822012(LAI)and 19812010(albedo and emissivity)at 15 km and 8-day resolutions,and the last two radiation products span the period 20082010 at 5 km and 3-h resolutions.These products have been evaluated and validated,and the preliminary results indicate that they are of higher quality and accuracy than the existing products.In particular,the first three products have much longer time series,and are therefore highly suitable for various environmental studies.This paper outlines the algorithms,product characteristics,preliminary validation results,potential applications and some examples of initial analysis of these products.
基金by the National Key Research and Development Program(2016YFA0602701)National Natural Science Foundation of China(31570468),Changjiang Young Scholars Programme of China(Q2016161)National Youth Top-Notch Talent Support Program,and Fok Ying Tung Education Foundation(151015).
文摘Background:Although soil erosion plays a key role in the carbon cycle,a holistic and mechanistic understanding of the soil erosion process within the cycle is still lacking.The aim of this study was therefore to improve our mechanistic understanding of soil organic carbon(SOC)and soil respiration dynamics through an experiment conducted in an eroding black soil farmland landscape in Northeast China.Results:The depositional profiles store 5.9 times more SOC than the eroding profiles and 3.3 times more SOC than the non-eroding profiles.A linear correlation between the SOC and 137Cs(Caesium-137)was observed in our study,suggesting that the SOC decreased with increased soil erosion.Furthermore,the fractions of intermediate C and the microaggregate C were lowest at the eroding position and highest at the depositional position.In the depositional topsoil,the input of labile materials plays a promotional role in soil respiration.Conversely,in the subsoil(i.e.,below 10 cm),the potential mineralization rates were lowest at the depositional position—due to effective stabilization by physical protection within soil microaggregates.The field results of soil surface respiration also suggest that the depositional topsoil SOC is prone to be mineralized and that SOC at this depositional context is stabilized at subsoil depth.In addition,the high water contents at the depositional position can limit the decomposition rates and stabilize the SOC at the same time.Conclusions:The findings from this study support that a majority of the SOC at footslope is stored within most of the soil profile(i.e.,below 10 cm)and submitted to long-term stabilization,and meanwhile support that the depositional profile emits more CO2 than the summit due to its high amount and quality of SOC.
基金supported by the National Key Research&Development Program of China(2018YFA0606001)the National Natural Science Foundation of China(41977404)。
文摘China’s high ambitions to reach peak CO_(2) emissions by 2030 and carbon neutrality by 2060 make carbon mitigation an urgent issue with widespread societal consequences.To develop an achievable roadmap and an effective portfolio of climate policies,it is essential that a clear picture of the magnitude and uncertainty of China’s current carbon balance is available,at both national and regional levels.
基金supported by the National Basic Research Program of China(2010CB950703)the National Natural Science Foundation of China(41571338)
文摘In this study, we explore the feasibility of optimizing ecosystem photosynthetic and respiratory parameters from the seasonal variation of the net carbon flux. An optimization scheme is proposed to estimate two key parameters(Vmax25and Q10) by exploiting the seasonal variation in the net ecosystem carbon flux retrieved by an atmospheric inversion system. This scheme is implemented to estimate Vmax25 and Q10of the boreal ecosystem productivity simulator(BEPS) to improve its NEP simulation in the boreal North American region. Then, in situ NEE observations at six eddy covariance sites are used to evaluate the NEE simulations from BEPS with initial and optimized parameters. The results show that the performance of the optimized BEPS is superior to that of the BEPS with the default parameter values. These results implicate that it is possible to optimize ecosystem model parameters by different sensitivities of Vmax25 and Q10during growing and non-growing seasons through atmospheric inversion or data assimilation techniques.
基金Key Project of Chinese Academy of Sciences(CAS)[grant number KJZD-EW-G03-04]National Key R&D Program of China[grant number 2017YFA0604801]+2 种基金One Hundred Person Project of CAS[grant number Y329k71002]National Science Foundation for Excellent Young Scholars of China[grant number 41322005]the CAS Interdisciplinary Innovation Team of the Chinese Academy of Sciences.
文摘Vegetation gross primary production(GPP)is an important variable for the carbon cycle on the Qinghai-Tibetan Plateau(QTP).Based on the measurements from 12 eddy covariance flux sites,we validated a light use efficiency model(i.e.EC-LUE)to evaluate the spatial-temporal patterns of GPP and the effect of environmental variables on QTP.In general,EC-LUE model performed well in predicting GPP at different time scale over QTP.Annual GPP over the entire QTP ranged from 575 to 703 Tg C,and showed a significantly increasing trend from 1982 to 2013.However,there were large spatial heterogeneities in long-term trends of GPP.Throughout the entire QTP,air temperature increase had a greater influence than solar radiation and precipitation(PREC)changes on productivity.Moreover,our results highlight the large uncertainties of previous GPP estimates due to insufficient parameterization and validations.When compared with GPP estimates of the EC-LUE model,most Coupled Model Intercomparison Project(CMIP5)GPP products overestimate the magnitude and increasing trends of regional GPP,which potentially impact the feedback of ecosystems to regional climate changes.
基金the High-Tech Research and Development Program of China(No.2009AA122100)the National Science and Technology Ministry(2012BAH29B02).
文摘PenmanMonteith(PM)theory has been successfully applied to calculate land surface evapotranspiration(ET)for regional and global scales.However,soil surface resistance,related to soil moisture,is always difficult to determine over a large region,especially in arid or semiarid areas.In this study,we developed an ET estimation algorithm by incorporating soil moisture control,a soil moisture index(SMI)derived from the surface temperature and vegetation index space.We denoted this ET algorithm as the PM-SMI.The PM-SMI algorithm was compared with several other algorithms that calculated soil evaporation using relative humidity,and validated with Bowen ratio measurements at seven sites in the Southern Great Plain(SGP)that were covered by grassland and cropland with low vegetation cover,as well as at three eddy covariance sites from AmeriFlux covered by forest with high vegetation cover.The results show that in comparison with the other methods examined,the PM-SMI algorithm significantly improved the daily ET estimates at SGP sites with a root mean square error(RMSE)of 0.91 mm/d,bias of 0.33 mm/d,and R^(2) of 0.77.For three forest sites,the PM-SMI ET estimates are closer to the ET measurements during the non-growing season when compared with the other three algorithms.At all the 10 validation sites,the PMSMI algorithm performed the best.PM-SMI 8-day ET estimates were also compared with MODIS 8-day ET products(MOD16A2),and the latter showed negligible bias at SGP sites.In contrast,most of the PM-SMI 8-day ET estimates are around the 1:1 line.
基金supported by the Guangdong Major Project of Basic and Applied Basic Research(grant number 2020B0301030004)the National Natural Science Foundation of China(grant numbers 31971458,41971275)+3 种基金the Special highlevel plan project of Guangdong Province(grant number 2016TQ03Z354)Innovation Group Project of Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)(grant number 311021009)the Guangdong Basic and Applied Basic Research Foundation(grant number 2020A151501091)GDAS Special Project of Science and Technology Development(grant number 2020GDASYL-20200102002).
文摘Relationships among productivity,leaf phenology,and seasonal variation in moisture and light availability are poorly understood for evergreen broadleaved tropical/subtropical forests,which contribute 25% of terrestrial productivity.On the one hand,as moisture availability declines,trees shed leaves to reduce transpiration and the risk of hydraulic failure.On the other hand,increases in light availability promote the replacement of senescent leaves to increase productivity.Here,we provide a comprehensive framework that relates the seasonality of climate,leaf abscission,and leaf productivity across the evergreen broadleaved tropical/subtropical forest biome.The seasonal correlation between rainfall and light availability varies from strongly negative to strongly positive across the tropics and maps onto the seasonal correlation between litterfall mass and productivity for 68 forests.Where rainfall and light covary positively,litterfall and productivity also covary positively and are always greater in the wetter sunnier season.Where rainfall and light covary negatively,litterfall and productivity are always greater in the drier and sunnier season if moisture supplies remain adequate;otherwise productivity is smaller in the drier sunnier season.This framework will improve the representation of tropical/subtropical forests in Earth system models and suggests how phenology and productivity will change as climate change alters the seasonality of cloud cover and rainfall across tropical/subtropical forests.
基金supported by the National Natural Science Foundation of China(31922053)the start-up fund of Hainan University(Grant No.KYQD(ZR)21096)the National Key R&D Program of China(2017YFA0604801).
基金supported by the National Natural Science Foundation of China(42141020)the Guangdong Provincial Department of Science and Technology(2019ZT08G090).
文摘The Glasgow Declaration on Forests signed at the recent UN Climate Change Conference(COP 26)committed to halting forest loss by 2030.141 countries and regions,collectively covering over 90%of global forest,endorsed this declaration.Avoiding forest loss can generally contribute to climate change mitigation;however,the impacts of the declaration on global carbon dioxide(CO_(2))emission reduction are still unclear.Here we show that the Glasgow Declaration,if implemented fully and in a timely fashion,could reduce 123 Gt CO_(2) of emission from 2021 to 2050.This study also highlights that any delays in implementing the declaration would decrease the avoided emission.Although the Glasgow Declaration is a milestone for mitigating climate change,the more ambitious afforestation plan is urgently needed to keep the global temperature rise to below 1.5C relative to pre-industrial levels.
基金The research is funded by the China National Funds for Distinguished Young Scientists(41925001).
文摘As the second largest producer of maize,China contributes 23%of global maize production and plays an important role in guaranteeing maize markets stability.In spite of its importance,there is no 30m spatial resolution distribution map of maize for all of China.This study used a time-weighted dynamic time warping method to identify planting areas of maize by comparing the similarity of time series of a satellite-based vegetation index at each pixel with a standard time series derived from known maize fields and mapped maize distribution from 2016 to 2020 over 22 provinces accounting for more than 99%of the maize planting area in China.Based on 18800 field-surveyed pixels at 30-meter spatial resolution,the distribution map yields 76.15%and 81.59%of producer’s and user’s accuracies averaged over the entire investigated provinces,respectively.Municipality-and county-level census data also show a good performance in reproducing the spatial distribution of maize.This study provides an approach to mapping maize over large areas based on a small volume of field survey data.
基金supported by the National Science Fund for Distinguished Young Scholars(41925001)National Youth Top-notch Talent Support Program(2015-48)+2 种基金Changjiang Young Scholars Programme of China(Q2016161)Fundamental Research Funds for the Central Universities(19lgjc02)the National Natural Science Foundation of China(41971018 and 31930072).
文摘It has been long established that the terrestrial vegetation in spring has stronger photosynthetic capability than in autumn.However,this study challenges this consensus by comparing photosynthetic capability of terrestrial vegetation between the spring and autumn seasons based on measurements of 100 in situ eddy covariance towers over global extratropical ecosystems.At the majority of these sites,photosynthetic capability,indicated by light use efficiency(LUE)and apparent quantum efficiency,is significantly higher in autumn than in spring,due to lower atmosphere vapor pressure deficit(VPD)at the same air temperature.Seasonal VPD differences also substantially explain the interannual variability of the differences in photosynthetic capability between spring and autumn.We further reveal that VPD in autumn is significantly lower than in spring over 74.14% of extratropical areas,based on a global climate dataset.In contrast,LUE derived from a data-driven vegetation production dataset is significantly higher in autumn in over 61.02% of extratropical vegetated areas.Six Earth system models consistently projected continuous larger VPD values in spring compared with autumn,which implies that the impacts on vegetation growth will long exist and should be adequately considered when assessing the seasonal responses of terrestrial ecosystems to future climate conditions.