古气候研究进展

总结回顾了二十年来古气候研究的进展,着重揭示古气候变化的事实.共分析了10个问题:(1)威尔逊旋回,(2)冰河时代,(3)生物大灭绝,(4)人类走出非洲,(5)第四纪冰期一间冰期旋回,(6)下一个冰期何时到来,(7)末次冰期冰盛期,(8)冰期气候的不稳定性,(9)全新世气候的不稳定性,(10)全新世气候变化趋势.     

冰期-间冰期旋回

第四纪(2.5 Ma BP)气候的一个重要特征就是冰期-间冰期旋回.目前我们正处于间冰期中,气候温暖.这个间冰期地质学家称为全新世,是从11.5 kaBP开始的,至今已延续了1万年以上.而在此之前是距我们最近的一次冰期,称为末次冰期.     

全新世气候

全新世指我们目前所在的间冰期.一般把新仙女木事件(YD)结束的时间(11.5 kaBP)作为全新世的开始.当前国际上对全新世的气候变化有3点共识:1)进入全新世温度大幅度回升,中全新世以后逐渐下降,20世纪由于人类活动的影响全球变暖;2)早全新世北半球亚非季风区气候湿润,5 kaBP以后逐渐变干,但是ENSO加强;3)在以上变化的背景下发生了若干次冷干事件,这些事件开始与结束均较迅速,所以也被为气候突变.     

地球何时进入下一个冰期?

从第四纪开始至今的2.5Ma气候特征为冰期-间冰期旋回。在100ka旋回中,间冰期长者可持续近30ka,而短者不足10ka。目前的间冰期已持续了11.5ka,显然面临着间冰期结束的威胁。     

过去0.8 Ma期间的地表温度数值模拟研究

使用一个改进的二维能量平衡模式模拟了过去0.8 Ma冰期-间冰期旋回期间北半球各纬度带的地表温度,并以65°N的地表温度为代表与南极冰芯记录进行了比较.通过敏感性试验,分析了日射量、温室气体、沙尘气溶胶强迫和水汽反馈的辐射-气候效应.结果显示,日射量变化不足以解释冰期-间冰期旋回期间北半球的地表温度变化,大气温室气体(...     

十种谬误:对有关二氧化碳/气候的争论持怀疑态度者的观点

作者以怀疑的眼光回顾了有关大气中CO_2增加引起的可能气候效应的争论。对一般认为的十种谬误或未经证实的论点进行了讨论,它们是: 1.模式比数据好; 2.政府认可即等于科学证实; 3.气候变化将表现出不连续性; 4.随气候变率气候变化的增加; 5.过去100年的变暖趋势清楚证明CO_2增加引起气候变暖正在来临; 6.破记录的高温表明CO_2增加引起升温,破记录的低温表明临近一个冰期; 7.CO_2的间接的气候效应比直接效应更重要; 8.即使许多模式建立者不能预测下一年度的气候,农民制定农业生产计划时仍使用气候变暖的预测; 9.由于树的生长期很长,森林尤其易受气候变暖的危害; 10.砍伐森林相当于使土地沙漠化。     

兰州不同时期黄土有机质碳同位素与气候的关系

基于兰州九州台黄土剖面的土壤有机质δ13C分析,讨论了兰州地区末次间冰期和全新世2个时期气候以及地表植被的变化特征.结果表明,该地区末次间冰期δ13C变化范围为-29.97‰～-25.52‰,平均值为-27.79‰;全新世δ13C变化范围在-20.82～-34.40‰之间,平均值为-28.99‰.从δ13C平均值来看,该地区在以上两个时期地表植被主要为C3植物.末次间冰期九州台剖面δ13C表现出3峰夹2谷的特征与同一时期深海SPECMAP曲线有着良好的对应,表明了该时期兰州地区的气候变化与全球是一致的,全新世土壤有机质δ13C所反映出的3个不同的变化阶段对应于早、中、晚全新世阶段.结合黄土高原其他剖面相应时期的土壤有机质δ13C的研究结果,我们观察到陕西关中地区的黄土剖面末次间冰期和全新世土壤有机质δ13C要大于黄土高原西部的兰州等地区,气候差异引起的地表植被中C3、C4植物比例不同是造成两地区土壤有机质δ13C差异的主要因素.研究结果表明,黄土高原土壤有机质δ13C是揭示该地区气候变化的一个良好代用指标.     

中国的新石器文化与水稻农业的发展

《全新世》(The Holocene)杂志2011年第22卷第6期刊登了环境考古专集。香港大学宗永强、华东师范大学陈中原等在编者按中指出,近十余年对全新世气候变化的研究有了长足的进步,人们注意到早全新世气候变暖在农业及人类社会发展中的作用,以及中全新世古文明的解体     

二十五年来我国气候变动及其与大气环流的关系

气候变化,不但有以万年计算的地质时代冰期与间冰期的变化,也有几千年来历史时期的变化。但是,与我们关系最密切的,还是周期为几十年到百年左右的气候振动。对于几年到十几年时间的气候变化,我们可以称为气候变动。这种气候变动往往是长期气候振动的一个片断,因此从气候振动角度来研究气候变动是非常必要的。我国多数气象台站是在解放后建立的,一般只有二十几年的资料,因此就要求我们从较长时期的气候振动来了解这二十几年的气候特点,这样才能正确运用二十几年的资料,来作长期预报和超长期预报。     

当代气候变化的趋势及原因分析

本文回顾了近百年来世界气候的变化趋势及近年来世界气候异常的概况;综合分析了当代气候变化的主要原因,尤其是CO_2及其他痕量气体浓度的变化对世界气候的影响;在综述国外一些近期研究成果基础上,对今后几十年及21世纪世界气候变化趋势作了初步估计——地面平均气温将可能在不断波动的过程中趋于变暖。同时,论述了由这种气候增暖所可能造成的环境后果,并就如何应付这种可能出现的气候冲击提出一些初步看法。     

An annotated bibliography on the greenhouse effect and climate change

The literature on climate change from an enhanced greenhouse effect is large and growing rapidly. The problems considered are increasingly inter-disciplinary. For these reasons many workers will find useful pointers to the literature in the fields interacting with, but outside of, their own. We present here an annotated bibliography on issues relating to changes in the concentrations of Earth's greenhouse gases. The areas covered include theory and numerical modelling of climate change; cycles involving carbon dioxide and other radiatively important trace gases; observations of climate change and the problems associated with those observations; paleoclimatology as it relates to previous changes in the greenhouse gases; the impacts on and interactions with managed and natural ecosystems from climate change; policy issues related to climate change and to the limitation of climate change; history of the study of the greenhouse effect; and some other causes of climate change. Selection of papers has been made to facilitate rapid introduction to most of the important issues and findings in an area. Over 600 articles, reports, and books are discussed.     

Global warming potentials modified for surface radiative forcing for use in surface energy balance models

The radiative impact of greenhouse gases in warming the Earth varies significantly, depending on whether one considers the forcing at the tropopause or at the surface. Compared to the former, the surface forcing for some greenhouse gases is reduced by the interference of water vapour. Hence, we calculate alternative surface global warming potentials (SGWPs) that are derived from the surface forcing radiation of greenhouse gases for potential use in surface radiative energy balance models (SREBMs). For gases with a large water vapour overlap, the SGWPs are typically 30% smaller than current GWPs; for gases with relatively little overlap, the SGWPs are larger by more than 33%. These results may be used in conjunction with SREBMs as an additional means of calculating climate change, and may lead to an altered emissions budget compared to that outlined by the current Kyoto agreement.     

The Role Of Halocarbons In The Climate Change Of The Troposphere And Stratosphere

Releases of halocarbons into the atmosphere over the last 50 years are among the factors that have contributed to changes in the Earth’s climate since pre-industrial times. Their individual and collective potential to contribute directly to surface climate change is usually gauged through calculation of their radiative efficiency, radiative forcing, and/or Global Warming Potential (GWP). For those halocarbons that contain chlorine and bromine, indirect effects on temperature via ozone layer depletion represent another way in which these gases affect climate. Further, halocarbons can also affect the temperature in the stratosphere. In this paper, we use a narrow-band radiative transfer model together with a range of climate models to examine the role of these gases on atmospheric temperatures in the stratosphere and troposphere. We evaluate in detail the halocarbon contributions to temperature changes at the tropical tropopause, and find that they have contributed a significant warming of ~0.4 K over the last 50 years, dominating the effect of the other well-mixed greenhouse gases at these levels. The fact that observed tropical temperatures have not warmed strongly suggests that other mechanisms may be countering this effect. In a climate model this warming of the tropopause layer is found to lead to a 6% smaller climate sensitivity for halocarbons on a globally averaged basis, compared to that for carbon dioxide changes. Using recent observations together with scenarios we also assess their past and predicted future direct and indirect roles on the evolution of surface temperature. We find that the indirect effect of stratospheric ozone depletion could have offset up to approximately half of the predicted past increases in surface temperature that would otherwise have occurred as a result of the direct effect of halocarbons. However, as ozone will likely recover in the next few decades, a slightly faster rate of warming should be expected from the net effect of halocarbons, and we find that together halocarbons could bring forward next century’s expected warming by ~20 years if future emissions projections are realized. In both the troposphere and stratosphere CFC-12 contributes most to the past temperature changes and the emissions projection considered suggest that HFC-134a could contribute most of the warming over the coming century.     

Commentary on “The Anthropogenic Greenhouse Era Began Thousands of Years Ago”

Bill Ruddiman (Climatic Change, 61, 261–293, 2003) recently suggested that early civilisations could have saved us from an ice age because land management over substantial areas caused an increase in atmospheric CO₂ concentration. Ruddiman suggests a decreasing “natural course” of the Holocene greenhouse gases concentrations and sea-level by referring to analogous situations in the past, namely the last three interglacials. An examination of marine isotopic stage 11 would perhaps make Ruddiman’s argument even more thought-challenging. Yet, the hypothesis of a natural lowering of CO₂ during the Holocene contradicts recent numerical simulations of the Earth carbon cycle during this period. We think that the only way to resolve this conflict is to properly assimilate the palæoclimate information in numerical climate models. As a general rule, models are insufficiently tested with respect to the wide range of climate situations that succeeded during the Pleistocene. In this comment, we present three definitions of palæoclimate information assimilation with relevant examples. We also present original results with the Louvain-la-Neuve climate-ice sheet model suggesting that if, indeed, the Holocene atmospheric CO₂ increase is anthropogenic, a late Holocene glacial inception is plausible, but not certain, depending on the exact time evolution of the atmospheric CO₂ concentration during this period.     

关于温室气体浓度变化及其引起的气候变化的几个问题

阐述了当前全球温室气体浓度的增加及其引起的气候效应,讨论了气候变化研究中存在的许多不确定性,如未来温室气体的浓度如何变化,未来气候如何变化,以及气候影响的评价问题等.最后,强调了未来气候变化基础研究中需要注意的问题.       

Analysis of temperature series in Europe in relation to the detection of the enhanced greenhouse effect

Summary A method is developed for analysing climate series. It is based on the assumption that climate undergoes abrupt changes by natural means. It is a generalization of an existing method for dividing a series into two parts. It is assumed that increasing concentrations of greenhouse gases will lead to a gradual climate change (trend) and that this change will be superimposed upon the natural abrupt changes (jumps). On the basis of these facts, jumps in the direction of a climate change resulting from the increased concentrations of greenhouse gases are expected to be stronger than those in the opposite direction and previous jumps in the same direction. Different criteria are used to support this assumption. The method of analysis is applied to time series of summer and winter temperatures of 13 European stations.The largest increases in temperature do not occur in the recent past; they occur around 1910 in winter and about 1930 in summer. As the test for detection of the enhanced greenhouse effect is made stricter, the assumption put forward becomes weaker. Most time series do not have significant trends within various sub-periods. Differences in variability between successive sub-periods are generally not significant. There is agreement between the results reported here and others in the literature. So far, there is no definite evidence that the increasing concentration of greenhouse gases is affecting the climate of Europe.With 6 Figures     

Acceleration technique for Milankovitch type forcing in a coupled atmosphere-ocean circulation model: method and application for the Holocene

A method is introduced which allows the calculation of long-term climate trends within the framework of a coupled atmosphere-ocean circulation model. The change in the seasonal cycle of incident solar radiation induced by varying orbital parameters has been accelerated by factors of 10 and 100 in order to allow transient simulations over the period from the mid-Holocene until today, covering the last 7,000 years. In contrast to conventional time-slice experiments, this approach is not restricted to equilibrium simulations and is capable to utilise all available data for validation. We find that opposing Holocene climate trends in tropics and extra-tropics are a robust feature in our experiments. Results from the transient simulations of the mid-Holocene climate at 6,000 years before present show considerable differences to atmosphere-alone model simulations, in particular at high latitudes, attributed to atmosphere-ocean-sea ice effects. The simulations were extended for the time period 1800–2000 AD, where, in contrast to the Holocene climate, increased concentrations of greenhouse gases in the atmosphere provide for the strongest driving mechanism. The experiments reveal that a Northern Hemisphere cooling trend over the Holocene is completely cancelled by the warming trend during the last century, which brings the recent global warming into a long-term context.     

国家发改委正式批准“我国温室气体监测分析系统建设实施方案（一期）”立项

中华人民共和国国家发展和改革委员会2008年10月正式批准“我国温室气体监测分析系统建设实施方案（一期）”立项,总经费5700万。中国气象科学研究院按要求于10月底之前编制上报了2个子项目的可行性研究报告。2009年3月,中国气象局职能司召集中国气象科学研究院、台站人员在京召开研讨会,对可研报告集中补充和修订,     

Did Humankind Prevent a Holocene Glaciation?

Recently, W.F. Ruddiman (2003, Climatic Change, Vol. 61, pp. 261–293) suggested that the anthropocene, the geological epoch of significant anthropospheric interference with the natural Earth system, has started much earlier than previously thought (P. I. Crutzen and E. F. Stoermer, 2000, IGBP Newsletter, Vol. 429, pp. 623–628). Ruddiman proposed that due to human land use, atmospheric concentrations of CO₂ and CH₄ began to deviate from their natural declining trends some 8000 and 5000 years ago, respectively. Furthermore, Ruddiman concluded that greenhouse gas concentrations grew anomalously thereby preventing natural large-scale glaciation of northern North America that should have occurred some 4000–5000 years ago without human interference. Here we would like to comment on (a) natural changes in atmospheric CO₂ concentration during the Holocene and (b) on the possibility of a Holocene glacial inception. We substantiate our comments by modelling results which suggest that the last three interglacials are not a proper analogue for Holocene climate variations. In particular, we show that our model does not yield a glacial inception during the last several thousand years even if a declining trend in atmospheric CO₂ was assumed.     

ASSESSING THE DICE MODEL: UNCERTAINTY ASSOCIATED WITH THE EMISSION AND RETENTION OF GREENHOUSE GASES

Analysis of the DICE model indicates that it contains unsupported assumptions, simple extrapolations, and misspecifications that cause it to understate the rate at which economic activity emits greenhouse gases and the rate at which the atmosphere retains greenhouse gases. The model assumes a world population that is 2 billion people lower than the base case' projected by demographers. The model extrapolates a decline in the quantity of greenhouse gases emitted per unit of economic activity that is possible only if there is a structural break in the economic and engineering factors that have determined this ratio over the last century. The model uses a single equation to simulate the rate at which greenhouse gases accumulate in the atmosphere. The forecast for the airborne fraction generated by this equation contradicts forecasts generated by models that represent the physical and chemical processes which determine the movement of carbon from the atmosphere to the ocean. When these unsupported assumptions, simple extrapolations, and misspecifications are remedied with simple fixes, the economic impact of global climate change increases several fold. Similarly, these remedies increase the impact of uncertainty on estimates for the economic impact of global climate change. Together, these results indicate that considerable scientific and economic research is needed before the threat of climate change can be dismissed with any degree of certainty.