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1.
Natural and anthropogenic climate change: incorporating historical land cover change,vegetation dynamics and the global carbon cycle 总被引：5，自引：0，他引：5
This study explores natural and anthropogenic influences on the climate system, with an emphasis on the biogeophysical and biogeochemical effects of historical land cover change. The biogeophysical effect of land cover change is first subjected to a detailed sensitivity analysis in the context of the UVic Earth System Climate Model, a global climate model of intermediate complexity. Results show a global cooling in the range of –0.06 to –0.22 °C, though this effect is not found to be detectable in observed temperature trends. We then include the effects of natural forcings (volcanic aerosols, solar insolation variability and orbital changes) and other anthropogenic forcings (greenhouse gases and sulfate aerosols). Transient model runs from the year 1700 to 2000 are presented for each forcing individually as well as for combinations of forcings. We find that the UVic Model reproduces well the global temperature data when all forcings are included. These transient experiments are repeated using a dynamic vegetation model coupled interactively to the UVic Model. We find that dynamic vegetation acts as a positive feedback in the climate system for both the all-forcings and land cover change only model runs. Finally, the biogeochemical effect of land cover change is explored using a dynamically coupled inorganic ocean and terrestrial carbon cycle model. The carbon emissions from land cover change are found to enhance global temperatures by an amount that exceeds the biogeophysical cooling. The net effect of historical land cover change over this period is to increase global temperature by 0.15 °C. 相似文献
2.
J. Hansen M. Sato R. Ruedy P. Kharecha A. Lacis R. Miller L. Nazarenko K. Lo G. A. Schmidt G. Russell I. Aleinov S. Bauer E. Baum B. Cairns V. Canuto M. Chandler Y. Cheng A. Cohen A. Del Genio G. Faluvegi E. Fleming A. Friend T. Hall C. Jackman J. Jonas M. Kelley N. Y. Kiang D. Koch G. Labow J. Lerner S. Menon T. Novakov V. Oinas Ja. Perlwitz Ju. Perlwitz D. Rind A. Romanou R. Schmunk D. Shindell P. Stone S. Sun D. Streets N. Tausnev D. Thresher N. Unger M. Yao S. Zhang 《Climate Dynamics》2007,29(7-8):661-696
We carry out climate simulations for 1880–2003 with GISS modelE driven by ten measured or estimated climate forcings. An ensemble
of climate model runs is carried out for each forcing acting individually and for all forcing mechanisms acting together.
We compare side-by-side simulated climate change for each forcing, all forcings, observations, unforced variability among
model ensemble members, and, if available, observed variability. Discrepancies between observations and simulations with all
forcings are due to model deficiencies, inaccurate or incomplete forcings, and imperfect observations. Although there are
notable discrepancies between model and observations, the fidelity is sufficient to encourage use of the model for simulations
of future climate change. By using a fixed well-documented model and accurately defining the 1880–2003 forcings, we aim to
provide a benchmark against which the effect of improvements in the model, climate forcings, and observations can be tested.
Principal model deficiencies include unrealistically weak tropical El Nino-like variability and a poor distribution of sea
ice, with too much sea ice in the Northern Hemisphere and too little in the Southern Hemisphere. Greatest uncertainties in
the forcings are the temporal and spatial variations of anthropogenic aerosols and their indirect effects on clouds.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
3.
气候变化的检测归因是历次IPCC评估报告的重要组成部分。检测归因的目标是检测并量化由外强迫引起的变化,识别人为和自然强迫对气候变化的相对贡献。有助于全面评估气候系统是如何受人类活动影响的,所得结论对未来气候变化预估的信度而言至关重要。检测归因模式比较计划(DAMIP)是第六次国际耦合模式比较计划(CMIP6)的一个子计划,共包含3个级别、多达14组不同强迫驱动下的试验。文中概述其科学背景、试验设计、参与模式情况,并评述该计划的意义、期待的产出以及中国的机遇和贡献,以期使读者迅速了解相关要点和进展,为利用这些模式模拟试验数据开展检测归因研究提供必要的参考。 相似文献
4.
《Atmospheric Science Letters》2001,2(1-4):132-142
We use globally gridded radiosonde temperature datasets in a simple climate change study. Two climate models, when run with historical and, particularly, anthropogenic forcings, exhibit a degree of agreement with radiosonde temperature observations for 1958–1998. 相似文献
5.
Simon F. B. Tett Richard Betts Thomas J. Crowley Jonathan Gregory Timothy C. Johns Andy Jones Timothy J. Osborn Elisabeth Öström David L. Roberts Margaret J. Woodage 《Climate Dynamics》2007,28(1):3-34
A climate simulation of an ocean/atmosphere general circulation model driven with natural forcings alone (constant “pre-industrial” land-cover and well-mixed greenhouse gases, changing orbital, solar and volcanic forcing) has been carried out from 1492 to 2000. Another simulation driven with natural and anthropogenic forcings (changes in greenhouse gases, ozone, the direct and first indirect effect of anthropogenic sulphate aerosol and land-cover) from 1750 to 2000 has also been carried out. These simulations suggest that since 1550, in the absence of anthropogenic forcings, climate would have warmed by about 0.1 K. Simulated response is not in equilibrium with the external forcings suggesting that both climate sensitivity and the rate at which the ocean takes up heat determine the magnitude of the response to forcings since 1550. In the simulation with natural forcings climate sensitivity is similar to other simulations of HadCM3 driven with CO2 alone. Climate sensitivity increases when anthropogenic forcings are included. The natural forcing used in our experiment increases decadal–centennial time-scale and large spatial scale climate variability, relative to internal variability, as diagnosed from a control simulation. Mean conditions in the natural simulation are cooler than in our control simulation reflecting the reduction in forcing. However, over certain regions there is significant warming, relative to control, due to an increase in forest cover. Comparing the simulation driven by anthropogenic and natural forcings with the natural-only simulation suggests that anthropogenic forcings have had a significant impact on, particularly tropical, climate since the early nineteenth century. Thus the entire instrumental temperature record may be “contaminated” by anthropogenic influences. Both the hydrological cycle and cryosphere are also affected by anthropogenic forcings. Changes in tree-cover appear to be responsible for some of the local and hydrological changes as well as an increase in northern hemisphere spring snow cover.
相似文献
| Simon F. B. TettEmail: |
6.
地球系统中的大气圈、水圈、冰雪圈、岩石圈和生物圈构成了气候系统, 气候系统中不同圈层之间的相互作用决定了气候的自然变化。由于人类活动的日益加剧, 对气候系统已经产生了显著影响。气候的自然变化和人类活动导致的气候变化对社会经济的发展以及人民生活的影响日益加大, 并涉及到国家安全、环境外交和可持续发展等一系列重大问题。要认识气候变化及其强迫因素、预测未来气候变化, 最基础的工作是建立针对气候目的涉及到气候系统五大圈层的综合气候观测系统, 以获取所需的高质量资料和相关产品, 提供气候系统变化的详细信息。该文回顾了气候观测系统设计在中国的发展以及中国气象科学研究院在组织设计中国气候观测系统中的作用, 并指出了在建立我国气候观测系统中存在的一些需要改进的方面。在对气候观测系统进行分析的基础上, 指出了与建立气候观测系统相关的10个方面的关键问题, 这些问题包括:气候观测系统的科学需求、气候观测系统的代表性、全面性、规范性、对气候预测和预估及模式发展的支撑性、多学科应用性、社会经济性、资料开放共享性以及气候系统资料的同化再分析和历史资料的抢救。 相似文献
7.
The contribution of anthropogenic forcings to regional changes in temperature during the last decade
Nikolaos Christidis Peter A. Stott Francis W. Zwiers Hideo Shiogama Toru Nozawa 《Climate Dynamics》2012,39(6):1259-1274
Regional distributions of the mean annual temperature in the 2000s are computed with and without the effect of anthropogenic influences on the climate in several sub-continental regions. Simulated global patterns of the temperature response to external forcings are regressed against observations using optimal fingerprinting. The global analysis provides constraints which are then used to construct the regional temperature distributions. A similar approach was also employed in previous work, but here the methodology is extended to examine changes in any region, including areas with a poor observational coverage that were omitted in the earlier study. Two different General Circulation Models (GCMs) are used in the analysis. Anthropogenic forcings are found to have at least quadrupled the likelihood of occurrence of a year warmer than the warmest year since 1900 in 23 out of the 24 regions. The temperature distributions computed with the two models are very similar. While a more detailed assessment of model dependencies remains to be made once additional suitable GCM simulations become available, the present study introduces the statistical methodology and demonstrates its first application. The derived information concerning the effect of human influences on the regional climate is useful for adaptation planning. Moreover, by pre-computing the change in the likelihood of exceeding a temperature threshold over a range of thresholds, this kind of analysis enables a near real-time assessment of the anthropogenic impact on the observed regional temperatures. 相似文献
8.
Bruce T. Anderson Jeff R. Knight Mark A. Ringer Clara Deser Adam S. Phillips Jin-Ho Yoon Annalisa Cherchi 《Climate Dynamics》2010,35(7-8):1461-1475
Understanding the historical and future response of the global climate system to anthropogenic emissions of radiatively active atmospheric constituents has become a timely and compelling concern. At present, however, there are uncertainties in: the total radiative forcing associated with changes in the chemical composition of the atmosphere; the effective forcing applied to the climate system resulting from a (temporary) reduction via ocean-heat uptake; and the strength of the climate feedbacks that subsequently modify this forcing. Here a set of analyses derived from atmospheric general circulation model simulations are used to estimate the effective and total radiative forcing of the observed climate system due to anthropogenic emissions over the last 50 years of the twentieth century. They are also used to estimate the sensitivity of the observed climate system to these emissions, as well as the expected change in global surface temperatures once the climate system returns to radiative equilibrium. Results indicate that estimates of the effective radiative forcing and total radiative forcing associated with historical anthropogenic emissions differ across models. In addition estimates of the historical sensitivity of the climate to these emissions differ across models. However, results suggest that the variations in climate sensitivity and total climate forcing are not independent, and that the two vary inversely with respect to one another. As such, expected equilibrium temperature changes, which are given by the product of the total radiative forcing and the climate sensitivity, are relatively constant between models, particularly in comparison to results in which the total radiative forcing is assumed constant. Implications of these results for projected future climate forcings and subsequent responses are also discussed. 相似文献
9.
G. C. Hegerl P. A. Stott M. R. Allen J. F. B. Mitchell S. F. B. Tett U. Cubasch 《Climate Dynamics》2000,16(10-11):737-754
Fingerprint techniques for the detection of anthropogenic climate change aim to distinguish the climate response to anthropogenic forcing from responses to other external influences and from internal climate variability. All these responses and the characteristics of internal variability are typically estimated from climate model data. We evaluate the sensitivity of detection and attribution results to the use of response and variability estimates from two different coupled ocean atmosphere general circulation models (HadCM2, developed at the Hadley Centre, and ECHAM3/LSG from the MPI für Meteorologie and Deutsches Klimarechenzentrum). The models differ in their response to greenhouse gas and direct sulfate aerosol forcing and also in the structure of their internal variability. This leads to differences in the estimated amplitude and the significance level of anthropogenic signals in observed 50-year summer (June, July, August) surface temperature trends. While the detection of anthropogenic influence on climate is robust to intermodel differences, our ability to discriminate between the greenhouse gas and the sulfate aerosol signals is not. An analysis of the recent warming, and the warming that occurred in the first half of the twentieth century, suggests that simulations forced with combined changes in natural (solar and volcanic) and anthropogenic (greenhouse gas and sulfate aerosol) forcings agree best with the observations. 相似文献
10.
An analytic solution of an energy balance model (EBM) is presented which can beused as a recursive filter for time series analysis. It is shown that the EBM can reproduce the solution of a coupled atmosphere-ocean general circulation model (AOGCM) experiment. Contrary to the AOGCM, the EBM easily allows for variations in climate sensitivity to satisfy the full range of uncertainty concerned with this parameter. The recursive filter is applied to two natural and two anthropogenic forcing mechanisms which are expressed in terms of heating rate anomaly time series: volcanism, solar activity, greenhouse gases (GHG), and anthropogenic tropospheric aerosols. Thus, we obtain modelled global mean temperature variations as a response to the different forcings and with respect to the uncertainty in the forcing approximations and climate sensitivity. In addition, it is shown that the observed (ENSO-corrected) global mean temperature time series within the period from 1866 to 1997 can be explained by the external forcings which have been considered and an additional white noise forcing. In this way we are able to separate different signals and compare them. As a result, global anthropogenic climate change due to GHG forcing can be detected at a high level of significance without considering spatial patterns of climate change but including natural forcing, which is usually not done. Furthermore, it is shown that solar forcing alone does not lead to significantclimate change, whereas solar and volcanic forcing together lead to a significant natural climate change signal. Anthropogenic climate change due to GHG forcing may partly be masked by anthropogenic aerosol cooling. 相似文献
11.
The results are presented of the statistical analysis of correspondence between the model simulations and observations of
temperature changes on the territory of Russia. Three model ensembles are considered, differing in the level of taking account
of the impact of external forcings on the climate system of the Earth. For each of them, the statistical correspondence is
estimated between the observed surface air temperature variations in the second half of the 20th century and at the beginning
of the 21st century and model simulations taking account of the natural variability typical of the climate system. The analysis
demonstrated that, in spite of the uncertainties associated with the differences in the representation of anthropogenic and
natural external forcings on the climate in model simulations as well as with the imperfection of climate models and with
internal variability of the climate system, the model experiments enable to obtain the relevant information both on the temporal
evolution of temperature changes on the territory of Russia and on their spatial peculiarities. 相似文献
12.
气候系统模式FGOALS_gl模拟的20世纪气温变化 总被引：1，自引：1，他引：0
分析了中国科学院大气物理研究所大气科学和地球流体力学国家重点实验室(LASG/IAP)发展的快速耦合气候系统模式FGOALS_gl对近100年气温变化的模拟,讨论了20世纪气温变化的机理。结果表明,在自然因素和人为因素的共同强迫作用下,FGOALS_gl能够合理再现20世纪全球平均和纬向平均地表气温随时间的演变。利用太阳辐照度等自然强迫、温室气体和气溶胶等人为强迫因子来驱动耦合模式,能够模拟出过去100年全球平均气温的增温趋势和年代际变化。耦合模式可以较好地模拟出20世纪全球气温变化趋势的空间分布。对区域气温变化模拟效果的分析表明,除北大西洋外,FGOALS_gl对其他地区具有较高的模拟技巧,表明外强迫是造成多数地区气温变化的主要原因。FGOALS_gl的主要缺陷在于模拟的变暖强度偏弱,大气模式自身的偏差以及耦合模式对温室气体响应的敏感度偏低是造成上述缺陷的主要原因。总体而言,FGOALS_gl对20世纪气温变化的模拟效果较为理想,特别是在全球、半球和大陆尺度上,该模式对过去100年气温变化的模拟较为合理。 相似文献
13.
尽管气候变化是全球性的现象,但其表现和结果随区域不同而不同,因此区域气候信息对于气候变化的作用和风险评估很重要。基于此,IPCC第六次评估报告（AR6）第一工作组（WGI）报告第十章对如何从全球链接到区域气候变化方面进行了评估。区域气候变化是对自然强迫和人类活动的区域响应、对大尺度气候系统内部变率的响应和区域气候本身反馈过程的相互作用结果。因此,本章重点关注如何从多套观测资料,不同模式的集合,物理过程的理解、专家判断和本地信息等多元信息中有效提炼出区域信息的方法。通过提炼方法指出人类活动是许多次大陆尺度上1950年代以来区域平均温度变化的主要驱动力,但参考时段和阈值的选择对人类活动信号是否出现和出现的早晚有影响。人类活动对一些区域的多年代际降水变化有一定贡献,但其不确定性相对全球平均而言更大。气候系统内部变率可以在很大程度上延迟和阻碍人类活动信号在区域气候变化中的出现。区域气候变化的评估给决策者提供了更多有用的信息,增加了评估报告的适用性。 相似文献
14.
In this study, the contributions from changes in man-made greenhouse gases (GHG), anthropogenic aerosols (AA), and land use (LU), as well as natural solar and volcanic (NAT) forcing changes, to observed changes in surface air temperature (T) and precipitation (P) over global land, especially over arid-semiarid areas, during 1946–2005 are quantified using observations and climate model simulations from the Coupled Model Intercomparison Project Phase 5 (CMIP5). Results show that the anthropogenic (ANT) forcings dominate the ubiquitous surface warming seen in observations and lead to slight increases in precipitation over most land areas, while the NAT forcing leads to small cooling over land. GHG increases are the primary factor responsible for the anthropogenic climate change, while the AA forcing offsets a large part of the GHG-induced warming and P changes. The LU forcing generally contributes little to the T and P changes from 1946 to 2005 over most land areas. Unlike the consistent temperature changes among most model simulations, precipitation changes display a large spread among the models and are incomparable with the observations in spatial distributions and magnitude, mainly due to its large internal variability that varies among individual model runs. Using an optimal fingerprinting method, we find that the observed warming over land during 1946–2005 can be largely attributed to the ANT forcings, and the combination of the ANT and NAT forcings can explain about 85~95% of the observed warming trend over global land as well as over most arid-semiarid regions such as Northern China. However, the anthropogenic influences on precipitation over the past 60 years are generally undetectable over most land areas, including most arid-semiarid regions. This indicates that internal variability is still larger than the forced change for land precipitation. 相似文献
15.
Angelo Rubino 《Theoretical and Applied Climatology》2011,106(3-4):473-479
Based on issues recently raised on the future of climate science, I present here a critical discussion which embraces the crucial aspects of the communication between climate scientists and laypersons, of the role confusing statements may exert on possible advancements in climate research, and of scientific priorities in climate science. I start distinguishing between different applications of climate models and identifying confusing uses of the words ??prediction?? and ??projection?? in recent discussions on climate modeling. Numerical models like those used in climate simulations are not assimilable to truly theories, nor can obtained results be considered as truly experimental evidences. Hence, it is hard to envisage the feasibility of crucial experiments through climate models. Increasing model resolution and complexity, although undoubtedly helpful for many applications related to a deeper understanding of the complex climate system and to substantial improvement of short-term forecasts, is not destined to change this fundamental limitation, to tackle the impossibility of predicting prominent climate forcings and to facilitate result comparisons against observations. Finally, as an example describing possible alternative resource allocations, I propose to devote more energy to strengthen the observational part of climate research, to focus on midterm forecasts, and to implement a new employment policy for climate scientists. In particular, through an increased and truly global in situ and remote sensing climate observing network, crucial experiments could emerge to challenge the fundamental basis of the conjecture of a great anthropogenic climate change, which, as known, is largely based on high climate sensitivities simulated by numerical models. 相似文献
16.
Five simple indices of surface temperature are used to investigate the influence of anthropogenic and natural (solar irradiance and volcanic aerosol) forcing on observed climate change during the twentieth century. These indices are based on spatial fingerprints of climate change and include the global-mean surface temperature, the land-ocean temperature contrast, the magnitude of the annual cycle in surface temperature over land, the Northern Hemisphere meridional temperature gradient and the hemispheric temperature contrast. The indices contain information independent of variations in global-mean temperature for unforced climate variations and hence, considered collectively, they are more useful in an attribution study than global mean surface temperature alone. Observed linear trends over 1950–1999 in all the indices except the hemispheric temperature contrast are significantly larger than simulated changes due to internal variability or natural (solar and volcanic aerosol) forcings and are consistent with simulated changes due to anthropogenic (greenhouse gas and sulfate aerosol) forcing. The combined, relative influence of these different forcings on observed trends during the twentieth century is investigated using linear regression of the observed and simulated responses of the indices. It is found that anthropogenic forcing accounts for almost all of the observed changes in surface temperature during 1946–1995. We found that early twentieth century changes (1896–1945) in global mean temperature can be explained by a combination of anthropogenic and natural forcing, as well as internal climate variability. Estimates of scaling factors that weight the amplitude of model simulated signals to corresponding observed changes using a combined normalized index are similar to those calculated using more complex, optimal fingerprint techniques. 相似文献
17.
Hong-Li Ren Fei Zheng Jing-Jia Luo Run Wang Minghong Liu Wenjun Zhang Tianjun Zhou Guangqing Zhou 《Acta Meteorologica Sinica》2020,34(1):43-62
Remarkable progress has been made in observations, theories, and simulations of the ocean-atmosphere system, laying a solid foundation for the improvement of short-term climate prediction, among which Chinese scientists have made important contributions. This paper reviews Chinese research on tropical air-sea interaction, ENSO dynamics, and ENSO prediction in the past 70 years. Review of the tropical air-sea interaction mainly focuses on four aspects: characteristics of the tropical Pacific climate system and ENSO; main modes of tropical Indian Ocean SSTs and their interactions with the tropical Pacific; main modes of tropical Atlantic SSTs and inter-basin interactions; and influences of the mid-high-latitude air-sea system on ENSO. Review of the ENSO dynamics involves seven aspects: fundamental theories of ENSO; diagnosis and simulation of ENSO; the two types of ENSO; mechanisms of ENSO initiation; the interactions between ENSO and other phenomena; external forcings and teleconnections; and climate change and the ENSO response. The ENSO prediction part briefly summarizes the dynamical-statistical methods used in ENSO prediction, as well as the operational ENSO prediction systems and their applications. Lastly, we discuss some of the issues in these areas that are in need of further study. 相似文献
18.
A reasonable past millennial climate simulation relies heavily on the specified external forcings, including both natural and anthropogenic forcing agents. In this paper, we examine the surface temperature responses to specified external forcing agents in a millennium-scale transient climate simulation with the fast version of LASG IAP Flexible Global Ocean-Atmosphere-Land System model (FGOALS-gl) developed in the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics (LASG/IAP). The model presents a reasonable performance in comparison with reconstructions of surface temperature. Differentiated from significant changes in the 20th century at the global scale, changes during the natural-forcing-dominant period are mainly manifested in the Northern Hemisphere. Seasonally, modeled significant changes are more pronounced during the wintertime at higher latitudes. This may be a manifestation of polar amplification associated with sea-ice-temperature positive feedback. The climate responses to total external forcings can explain about half of the climate variance during the whole millennium period, especially at decadal timescales. Surface temperature in the Antarctic shows heterogeneous and insignificant changes during the preindustrial period and the climate response to external forcings is undetectable due to the strong internal variability. The model response to specified external forcings is modulated by cloud radiative forcing (CRF). The CRF acts against the fluctuations of external forcings. Effects of clouds are manifested in shortwave radiation by changes in cloud water during the natural-forcing-dominant period, but mainly in longwave radiation by a decrease in cloud amount in the anthropogenic-forcing-dominant period. 相似文献
19.
This paper reviews recent progress in climate change attribution studies. The focus is on the attribution of observed long-term changes in surface temperature, precipitation, circulation, and extremes, as well as that of specific extreme weather and climate events. Based on new methods and better models and observations, the latest studies further verify the conclusions on climate change attribution in the IPCC AR5, and enrich the evidence for anthropogenic influences on weather and climate variables and extremes. The uncertainty of global temperature change attributable to anthropogenic forcings lies in the considerable uncertainty of estimated total radiative forcing due to aerosols, while the uncertainty of precipitation change attribution arises from the limitations of observation and model simulations along with influences from large internal variability. In terms of extreme weather and climate events, it is clear that attribution studies have provided important new insights into the changes in the intensity or frequency of some of these events caused by anthropogenic climate change. The framing of the research question, the methods selected, and the model and statistical methods used all have influences on the results and conclusions drawn in an event attribution study. Overall, attribution studies in China remain inadequate because of limited research focus and the complexity of the monsoon climate in East Asia. Attribution research in China has focused mainly on changes or events related to temperature, such as the attribution of changes in mean and extreme temperature and individual heat wave events. Some progress has also been made regarding the pattern of changes in precipitation and individual extreme rainfall events in China. Nonetheless, gaps remain with respect to the attribution of changes in extreme precipitation, circulation, and drought, as well as to the event attribution such as those related to drought and tropical cyclones. It can be expected that, with the continual development of climate models, ongoing improvements to data, and the introduction of new methods in the future, climate change attribution research will develop accordingly. Additionally, further improvement in climate change attribution will facilitate the development of operational attribution systems for extreme events, as well as attribution studies of climate change impacts. 相似文献
20.
We test for causality between radiative forcing and temperature using multivariate time series models and Granger causality tests that are robust to the non-stationary (trending) nature of global climate data. We find that both natural and anthropogenic forcings cause temperature change and also that temperature causes greenhouse gas concentration changes. Although the effects of greenhouse gases and volcanic forcing are robust across model specifications, we cannot detect any effect of black carbon on temperature, the effect of changes in solar irradiance is weak, and the effect of anthropogenic sulfate aerosols may be only around half that usually attributed to them. 相似文献