Climate sensitivity is an important index that measures the relationship between the increase in greenhouse gases and the magnitude of global warming.Uncertainties in climate change projection and climate modeling are...Climate sensitivity is an important index that measures the relationship between the increase in greenhouse gases and the magnitude of global warming.Uncertainties in climate change projection and climate modeling are mostly related to the climate sensitivity.The climate sensitivities of coupled climate models determine the magnitudes of the projected global warming.In this paper,the authors thoroughly review the literature on climate sensitivity,and discuss issues related to climate feedback processes and the methods used in estimating the equilibrium climate sensitivity and transient climate response（TCR）,including the TCR to cumulative CO2 emissions.After presenting a summary of the sources that affect the uncertainty of climate sensitivity,the impact of climate sensitivity on climate change projection is discussed by addressing the uncertainties in 2℃ warming.Challenges that call for further investigation in the research community,in particular the Chinese community,are discussed.展开更多
This study shows that the heretofore assumed condition for no temperature-profile (TP)/lapse-rate feedback, for all altitudes z, or , in fact yields a negative feedback. The correct condition for no TP feedback is for...This study shows that the heretofore assumed condition for no temperature-profile (TP)/lapse-rate feedback, for all altitudes z, or , in fact yields a negative feedback. The correct condition for no TP feedback is for all z, where Ts is the surface temperature. This condition translates into a uniform increase (decrease) in lapse rate with altitude for an increase (decrease) in Ts. The temperature changes caused by a change in solar irradiance and/or planetary albedo satisfy the condition for no TP feedback. The temperature changes caused by a change in greenhouse gas concentration do not satisfy the condition for no TP feedback and, instead, yield a positive feedback.展开更多
The atmospheric latent energy and incoming energy fluxes of the atmosphere are analyzed here based on the historical simulations of nine coupled models from the Coupled Model Intercomparison Project Phase 5 （CMIP5） ...The atmospheric latent energy and incoming energy fluxes of the atmosphere are analyzed here based on the historical simulations of nine coupled models from the Coupled Model Intercomparison Project Phase 5 （CMIP5） and two reanalysis datasets. The globally averaged atmospheric latent energy is found to be highly correlated with several types of energy flux, particularly the surface latent heat flux, atmosphere absorbed solar radiation flux, and surface net radiation flux. On the basis of these connections, a hydrological cycle controlled feedback （HCCF） is hypothesized. Through this feedback, the atmosphere absorbed solar radiation is enhanced and causes intensification of the surface latent heat flux when the atmospheric latent energy is abnormally strong. The representativeness of the HCCF during different periods and over different latitudinal zones is also discussed. Although such a feedback cannot be confirmed by reanalysis, it proves to be a common mechanism for all the models studied.展开更多
Coral reefs produce atmospheric dimethylsulfide (DMSa) which oxidises to non-sea-salt (nss) sulfate aerosols, precursors of cloud condensation nuclei (CCN) and low level cloud (LLC), reducing solar radiation and regul...Coral reefs produce atmospheric dimethylsulfide (DMSa) which oxidises to non-sea-salt (nss) sulfate aerosols, precursors of cloud condensation nuclei (CCN) and low level cloud (LLC), reducing solar radiation and regulating sea surface temperatures (SSTs). Here we report measurements of solar radiation, SST, LLC, DMS flux, , and rainfall before, during and after a major coral bleaching event at Magnetic Island in the central Great Barrier Reef (GBR). Measurements are compared with those made at the nearby fringing reef of Or-pheus Island where coral bleaching did not occur. Extreme solar radiation levels occurred from November to late January and could have reflected cloud radiative effects that increased downwelling of solar radiation. High levels of LLC often coincided with high periodic fluxes of DMS from the unbleached coral reef at Orpheus Island (e.g. 14 - 20 μmol·m-2·d-1), in direct contrast to the very low fluxes of DMS that were emitted from the bleached, human-impacted Magnetic Island fringing reef (nd-0.8 μmol·m-2·d-1) when SSTs were >30°C. Continuous SSTs measurements at the Magnetic Island reef revealed various heating and cooling periods, interspersed with stable SSTs. Cooling periods (negative climate feedback) ranged from -1°C to -3°C (7 day mean -1.6°C), and often seemed to occur during low tides, periodic pulses of DMS flux and LLC, keeping SSTs °C. In contrast warming periods of +1°C to +3°C (positive climate feedback, 7 day mean +1.52°C), seemed to occur during increasing tides, decreasing DMS flux and low to medium levels of LLC which increased solar radiation and caused SSTs over 30°C and corals to bleach. Alternation between these two states or types of feedback is indicated in this research and may be a function of enhanced scattering of solar radiation from nss-sulfate aerosols that originate from oxidation of DMSa produced from the coral reefs in the GBR. The net radiative forcing from clouds can be as high as four times as large as the radiative forcing from a doubling of 展开更多
城市化影响着局地与区域气候变化。区域气候模式是探讨城市与环境问题演变机制与城市化气候效应的重要研究手段,然而模式地表参数化方法处理地表参数时难以全面反映下垫面状况,可能影响模拟结果的合理性。因此以卫星数据源为基础,分析了...城市化影响着局地与区域气候变化。区域气候模式是探讨城市与环境问题演变机制与城市化气候效应的重要研究手段,然而模式地表参数化方法处理地表参数时难以全面反映下垫面状况,可能影响模拟结果的合理性。因此以卫星数据源为基础,分析了OPI方法处理下垫面参数导致的偏差,结合其导致的地表辐射收支差异说明不同空间尺度偏差的辐射收支效应,进而通过与CO2排放关联定量分析OPI方法对城市化气候效应的影响。结果发现随着空间尺度的变大,OPI方法导致的城市面积提取误差也在变大,导致城市下垫面转变成了其周边的土地覆盖类型,增强了城市群区域的反照率,降低了城市区域的辐射收支,弱化了城市气候效应。研究发现城市地表单位面积反照率增加0.01相当于减少了2.82kg的CO2排放,京津冀城市群2009年案例分析表明其弱化程度相当于减少了CO2排放2.28×105 t,扩展到中国区域尺度上则相当于减少了1.81×106 t CO2排放。展开更多
基金Supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(XDA05110300)National Natural Science Foundation of China(41330423)
文摘Climate sensitivity is an important index that measures the relationship between the increase in greenhouse gases and the magnitude of global warming.Uncertainties in climate change projection and climate modeling are mostly related to the climate sensitivity.The climate sensitivities of coupled climate models determine the magnitudes of the projected global warming.In this paper,the authors thoroughly review the literature on climate sensitivity,and discuss issues related to climate feedback processes and the methods used in estimating the equilibrium climate sensitivity and transient climate response（TCR）,including the TCR to cumulative CO2 emissions.After presenting a summary of the sources that affect the uncertainty of climate sensitivity,the impact of climate sensitivity on climate change projection is discussed by addressing the uncertainties in 2℃ warming.Challenges that call for further investigation in the research community,in particular the Chinese community,are discussed.
文摘This study shows that the heretofore assumed condition for no temperature-profile (TP)/lapse-rate feedback, for all altitudes z, or , in fact yields a negative feedback. The correct condition for no TP feedback is for all z, where Ts is the surface temperature. This condition translates into a uniform increase (decrease) in lapse rate with altitude for an increase (decrease) in Ts. The temperature changes caused by a change in solar irradiance and/or planetary albedo satisfy the condition for no TP feedback. The temperature changes caused by a change in greenhouse gas concentration do not satisfy the condition for no TP feedback and, instead, yield a positive feedback.
基金Supported by the National Basic Research Program of China(2010CB950503)West Light Foundation of the Chinese Academy of Sciences to Han Bo,National Natural Science Foundation of China(41205005 and 41130961)+1 种基金100-Talent Program of the Chinese Academy of Sciences to Gao YanhongExcellent Young Scholars Fund of CAREERI(Y451251001)
文摘The atmospheric latent energy and incoming energy fluxes of the atmosphere are analyzed here based on the historical simulations of nine coupled models from the Coupled Model Intercomparison Project Phase 5 （CMIP5） and two reanalysis datasets. The globally averaged atmospheric latent energy is found to be highly correlated with several types of energy flux, particularly the surface latent heat flux, atmosphere absorbed solar radiation flux, and surface net radiation flux. On the basis of these connections, a hydrological cycle controlled feedback （HCCF） is hypothesized. Through this feedback, the atmosphere absorbed solar radiation is enhanced and causes intensification of the surface latent heat flux when the atmospheric latent energy is abnormally strong. The representativeness of the HCCF during different periods and over different latitudinal zones is also discussed. Although such a feedback cannot be confirmed by reanalysis, it proves to be a common mechanism for all the models studied.
文摘Coral reefs produce atmospheric dimethylsulfide (DMSa) which oxidises to non-sea-salt (nss) sulfate aerosols, precursors of cloud condensation nuclei (CCN) and low level cloud (LLC), reducing solar radiation and regulating sea surface temperatures (SSTs). Here we report measurements of solar radiation, SST, LLC, DMS flux, , and rainfall before, during and after a major coral bleaching event at Magnetic Island in the central Great Barrier Reef (GBR). Measurements are compared with those made at the nearby fringing reef of Or-pheus Island where coral bleaching did not occur. Extreme solar radiation levels occurred from November to late January and could have reflected cloud radiative effects that increased downwelling of solar radiation. High levels of LLC often coincided with high periodic fluxes of DMS from the unbleached coral reef at Orpheus Island (e.g. 14 - 20 μmol·m-2·d-1), in direct contrast to the very low fluxes of DMS that were emitted from the bleached, human-impacted Magnetic Island fringing reef (nd-0.8 μmol·m-2·d-1) when SSTs were >30°C. Continuous SSTs measurements at the Magnetic Island reef revealed various heating and cooling periods, interspersed with stable SSTs. Cooling periods (negative climate feedback) ranged from -1°C to -3°C (7 day mean -1.6°C), and often seemed to occur during low tides, periodic pulses of DMS flux and LLC, keeping SSTs °C. In contrast warming periods of +1°C to +3°C (positive climate feedback, 7 day mean +1.52°C), seemed to occur during increasing tides, decreasing DMS flux and low to medium levels of LLC which increased solar radiation and caused SSTs over 30°C and corals to bleach. Alternation between these two states or types of feedback is indicated in this research and may be a function of enhanced scattering of solar radiation from nss-sulfate aerosols that originate from oxidation of DMSa produced from the coral reefs in the GBR. The net radiative forcing from clouds can be as high as four times as large as the radiative forcing from a doubling of
文摘城市化影响着局地与区域气候变化。区域气候模式是探讨城市与环境问题演变机制与城市化气候效应的重要研究手段,然而模式地表参数化方法处理地表参数时难以全面反映下垫面状况,可能影响模拟结果的合理性。因此以卫星数据源为基础,分析了OPI方法处理下垫面参数导致的偏差,结合其导致的地表辐射收支差异说明不同空间尺度偏差的辐射收支效应,进而通过与CO2排放关联定量分析OPI方法对城市化气候效应的影响。结果发现随着空间尺度的变大,OPI方法导致的城市面积提取误差也在变大,导致城市下垫面转变成了其周边的土地覆盖类型,增强了城市群区域的反照率,降低了城市区域的辐射收支,弱化了城市气候效应。研究发现城市地表单位面积反照率增加0.01相当于减少了2.82kg的CO2排放,京津冀城市群2009年案例分析表明其弱化程度相当于减少了CO2排放2.28×105 t,扩展到中国区域尺度上则相当于减少了1.81×106 t CO2排放。
