全球变暖趋缓研究进展

近十几年来,全球年平均表面温度上升趋势显示出停滞状态,即全球变暖趋缓,这引起了国际社会的广泛关注,同时也引发了对全球变暖的质疑,各国气候学家正努力就全球变暖趋缓的事实、原因及其可能影响展开研究。本文综述了目前国内外对全球变暖趋缓的研究结果。多数科学家认可近十几年来全球变暖停滞的事实,并认为太阳活动处于低位相、大气气溶胶（自然和人为）增加以及海洋吸收热量是变暖停滞的可能影响因子,其中海洋（尤其是700米以下的深海）对热量的储存可能是变暖停滞的关键。国际耦合模式比较计划第5阶段中的模式并未精确地描述各种有利降温影响因子的近期位相演变,因而其模拟的近期增暖趋势较观测偏强。由此推断,变暖停滞主要是自然因素造成的,并且预测变暖趋缓将在近几年或几十年内结束（依赖于太平洋年代际振荡的位相转变）,未来气温将仍主要受到温室气体增加的影响而表现出明显的上升趋势。因此,目前的全球变暖趋缓不大可能改变到本世纪末全球大幅度变暖带来的风险。本综述展望未来的研究热点包括:精确估算全球气温和海洋热含量的变率及其不确定性,海洋年代际信号（太平洋以及大西洋的年代际振荡）的转型机制,存储在深海的热量将在何时返回海洋表面及其对区域气候的潜在影响。     

人类排放情景的设计与全球变暖预估

<正>1气候变化的原因全球气候变化除地球系统内部变率外,自然强迫和人为强迫是重要的外部驱动力。其中自然强迫包括太阳活动和火山活动。人为强迫即人类活动,包括大量化石燃料燃烧排放温室气体、土地利用,以及气溶胶与污染排放等,其强度取决于人口发展与变化、社会经济发展、技术变化及其内部的协调性等。本文重点给出人类强迫的影响。IPCC第六次评估报告明确表明,近百年特别是近几十年来观测到的全球变暖归因为人类活动的影响,     

全球变暖中的科学问题

2013年各国政府间气候变化专门委员会（IPCC）第一工作组发布了第五次气候变化科学评估报告,以大量的观测分析和气候模式模拟证据,继续强调由于人类排放增加,全球正在变暖,未来将继续变暖的观点。本文综述研究全球变暖的几个深层次的科学问题,即多套全球气温观测资料的差异、不同标准气候态时段的作用、20世纪全球变暖的检测和归因及未来全球气温变化的走向,以此提出需进一步研究的科学问题。结果表明;需要进一步提高观测资料的质量;注意不同标准气候态时段对应的数值的不同;应进一步改善气候模式模拟年代际变率的能力及研究近15 a全球变暖减缓和停滞的原因,从而改善气候模式的模拟效果;造成预估未来全球气候变化的不确定性主要来自气候模式的差异、未来排放情景的差异及气候系统内部变率影响和自然外强迫的作用。     

近20 a驱动北极夏季迅速增暖和融冰的自然因素及过程

北极是全球气候系统平衡的重要一环,近20 a全球变暖现象中,北极迅速增温及融冰是最为引人关注的问题之一.人类影响无疑是过去几十年北极变暖背后的最主要的原因及驱动力,但气候系统的内在自然变率对北极的影响也不容忽视.本文指出,北极变暖的自然影响因子有一部分来源于热带太平洋东部海温的变化,热带太平洋通过由东部海温异常所驱动的...     

夏季亚洲-太平洋涛动的耦合模式模拟

亚洲-太平洋涛动是夏季欧亚大陆东部(15°—50°N,60°—120°E)与北太平洋上空(15°—50°N,180°—120°W)温度场反相变化的现象。亚洲-太平洋涛动指数由对流层上层(500—200 hPa)温度定义,反映了亚洲-太平洋纬向热力差异。基于一个全球海-气耦合模式FGOALS_gl的20世纪气候模拟试验结果,讨论了其对20世纪亚洲-太平洋涛动指数变化的模拟能力。结果表明,较之ERA-40再分析资料(1960—1999年),模式很好地刻画出上层温度场的平均态和主导模态的空间型。从趋势上看,模式对北太平洋上空温度的年代际变化和趋势模拟较好,但未能模拟出亚洲东部陆地上空的降温趋势。从频谱分析结果看,模拟的亚洲-太平洋涛动指数2—3,a的年际变率与再分析资料相当,5-7 a周期的变率较弱。模式能够较好地模拟出与亚洲-太平洋涛动指数相关的亚洲季风区气候异常。在20世纪模拟中,外强迫因子会改变耦合系统的年际变率,在自然因子强迫下亚洲-太平洋涛动指数的功率谱向低频方向增强,人为强迫因子的作用则相反。自然强迫因子和人为强迫因子在不同时期对亚洲-太平洋涛动年际和年代际变率的作用不同。在年际变率中人为强迫因子能够控制亚洲-太平洋涛动的变率使其不致过大;在年代际变率中人为强迫因子会增强自然强迫下亚洲-太平洋涛动的变率。模式上层温度的主导模态受ENSO调制,可能影响亚洲-太平洋涛动的年际变率。因此,模式对ENSO模拟能力的缺陷是制约模式对流层上层温度及亚洲-太平洋涛动指数变率的重要因素。     

论东亚夏季风的特征、驱动力与年代际变化

本文是以新的资料和研究结果对东亚夏季风的基本特征、驱动力和年代际变化所作的重新分析与评估。内容包括四个部分:（1）东亚夏季风的基本特征;（2）东亚夏季风的驱动力;（3）东亚夏季风的年代际变率与原因;（4）东亚夏季风与全球季风的关系。结果表明:东亚夏季风是亚洲夏季风的一个重要有机部分,主要由来源于热带的季风气流组成,并随季节由南向北呈阶段性推进,它是形成夏季东亚天气与气候的主要环流和降水系统。驱动夏季风的主要强迫有三部分:外部强迫、耦合强迫与内部变率,其中人类活动引起的外强迫（气候变暖、城市化、气溶胶增加等）是新出现的外强迫,它正不断改变着东亚夏季风的特征与演变趋势。海洋与陆面耦合强迫作为自然因子是引起东亚夏季风年际和年代际变化的主要原因,其中太平洋年代尺度振荡（PDO）与北大西洋多年代尺度振荡（AMO）的协同作用是造成东亚夏季风30~40年周期振荡的主要原因。1960年代以后,东亚夏季风经历了强—弱—强的年代际变化,相应的中国东部夏季降水型出现了“北多南少”向“南涝北旱”以及“北方渐增”的转变。最近的研究表明,上述东亚夏季风年代际变化与整个亚非夏季风系统的变化趋势是一致的。在本世纪主要受气候变暖的影响,夏季风雨带将持续北移,中国北方和西部地区出现持续性多雨的格局。最后本文指出,亚非夏季风系统相比于其他区域季风系统更适合全球季风的概念。     

海洋环流对全球增暖趋势的调制：基于FGOALS-s2的数值模拟研究

在工业革命以来全球长期增暖趋势背景下,全球平均表面气温还同时表现出年代际变化特征,二者叠加在一起使得全球平均气温在某些年份增暖相对停滞(如1999～2008年)或者增暖相对较快(如1980～1998年).利用中国科学院大气物理研究所大气科学和地球流体力学数值模拟国家重点实验室(LASG)发展的耦合气候模式FGOALS-s2历史气候和典型路径浓度(RCPs)模拟试验结果研究了可能造成全球增暖的年代际停滞及加速现象的原因,特别是海洋环流对全球变暖趋势的调制作用.该模式模拟的全球平均气温与观测类似,即在长期增暖趋势之上,还叠加了显著的年代际变化.对全球平均能量收支分析表明,模拟的气温年代际变化与大气顶净辐射通量无关,意味着年代际表面气温变化可能与能量在气候系统内部的重新分配有关.通过对全球增暖加速和停滞时期大气和海洋环流变化的合成分析及回归分析,发现全球表面气温与大部分海区海表温度(SST)均表现出几乎一致的变化特征.在增暖停滞时期,SST降低,更多热量进入海洋次表层和深层,使其温度增加;而在增暖加速时期,更多热量停留在表层,使得大部分海区SST显著增加,次表层海水和深海相对冷却.进一步分析表明,热带太平洋表层和次表层海温年代际变化主要是由于副热带—热带经圈环流(STC)的年代际变化所致,然后热带太平洋海温异常可以通过风应力和热通量强迫作用引起印度洋、大西洋海温的年代际变化.在此过程中,海洋环流变化起到了重要作用,例如印度尼西亚贯穿流(ITF)年代际异常对南印度洋次表层海温变化起到关键作用,而大西洋经圈翻转环流(AMOC)则能直接影响到北大西洋深层海温变化.     

基于慢特征分析方法研究陆地表面气温变率的驱动力

慢特征分析（SFA）方法可以从非平稳时间序列中提取出慢变的外强迫信息。近年来,SFA方法被应用于气候变化研究领域,用于探究气候变化的潜在驱动力及相关的动力学机制。本文基于SFA方法,提取全球陆地表面气温（LSAT）的慢变外强迫信息,研究全球LSAT慢变驱动力的空间结构特征及低频变率的主要驱动因子。SFA方法提取的LSAT慢变驱动力与历史时期全球辐射强迫（GRF）和全球海表温度（SST）的主模态（大西洋多年代际振荡AMO、热带太平洋ENSO变率和太平洋年代际振荡PDO）有显著的相关关系,表明全球大部分地区LSAT的变率受到GRF和三个SST模态的显著影响。GRF对LSAT变率的影响有全球一致性的特征,而三个SST模态对LSAT变率的影响则呈现出明显的区域特点。此外,由于SFA方法可以有效降低原始LSAT序列中随机噪声的干扰,GRF和SST模态对LSAT变率的解释方差显著提高,进一步表明GRF和SST模态是全球LSAT低频变率主要的驱动因子。最后,利用历史海温驱动AGCM试验（即AMIP试验）的结果,验证了三个SST模态对区域LSAT变率的显著影响。     

气候变暖的归因研究

气候变暖的成因是目前国际上的一个争议焦点,代表国际主流思想的4次IPCC评估报告[1-4]认为是人类活动的影响造成了变暖,其中包括温室效应加剧使气候变暖,而气溶胶的直接和间接影响则抵消了一部分变暖.但是,从20世纪末至今对气候变暖持怀疑观点的科学家,仍然不断对气候变暖的原因提出质疑[5 7].所以气候变暧的归因研究仍然是国际上的热门问题.     

工业化以来全球平均温度上升了1℃北大核心CSCD

全球变暖已经得到了公众、政府机构和科学家的广泛认知[1-3].但是,对于全球是否变暖以及这个变暖是否由人类活动造成,却依然不断受到质疑.这种质疑在2009年达到巅峰,同年出版的非政府间国际气候变化专门委员会(NIPCC)报告[4],对政府间气候变化专门委员会(IPCC)的观点[5]提出全面的质疑.最新的一轮质疑是2012年1月27日《华尔街日报》刊登了Allegre等16位科学家的署名文章[6],认为近10年地球气候没有变暖,呼吁不要压制气候变暖怀疑论者的声音.这说明尽管全球变暖的证据日益增加、全球变暖的观点得到越来越多的承认,但是对全球变暖这个事实的论证却绝不是多余的.     

Evidence for the role of the Atlantic multidecadal oscillation and the ocean heat uptake in hiatus prediction

The recent hiatus in global temperature at the surface has been analysed by several studies, mainly using global climate models. The common accepted picture is that since the late 1990s, the increase in anthropogenic radiative forcings has been counterbalanced by other factors, e.g., a decrease in natural forcings, augmented ocean heat storage and negative phases of ocean–atmosphere-coupled oscillation patterns. Here, simple vector autoregressive models are used for forecasting the temperature hiatus in the period 2001–2014. This gives new insight into the problem of understanding the ocean contribution (in terms of heat uptake and atmosphere–ocean-coupled oscillations) to the appearance of this recent hiatus. In particular, considering data about the ocean heat content until a depth of 700 m and the Atlantic multidecadal oscillation is necessary for correctly forecasting the hiatus, so catching both trend and interannual variability. Our models also show that the ocean heat uptake is substantially driven by the natural component of the total radiative forcing at a decadal time scale, confining the importance of the anthropogenic influences to a longer range warming of the ocean.     

Optimal detection and attribution of climate change: sensitivity of results to climate model differences

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.     

A transient climate change simulation with greenhouse gas and aerosol forcing: projected climate to the twenty-first century

 The potential climatic consequences of increasing atmospheric greenhouse gas (GHG) concentration and sulfate aerosol loading are investigated for the years 1900 to 2100 based on five simulations with the CCCma coupled climate model. The five simulations comprise a control experiment without change in GHG or aerosol amount, three independent simulations with increasing GHG and aerosol forcing, and a simulation with increasing GHG forcing only. Climate warming accelerates from the present with global mean temperatures simulated to increase by 1.7 °C to the year 2050 and by a further 2.7 °C by the year 2100. The warming is non-uniform as to hemisphere, season, and underlying surface. Changes in interannual variability of temperature show considerable structure and seasonal dependence. The effect of the comparatively localized negative radiative forcing associated with the aerosol is to retard and reduce the warming by about 0.9 °C at 2050 and 1.2 °C at 2100. Its primary effect on temperature is to counteract the global pattern of GHG-induced warming and only secondarily to affect local temperatures suggesting that the first order transient climate response of the system is determined by feedback processes and only secondarily by the local pattern of radiative forcing. The warming is accompanied by a more active hydrological cycle with increases in precipitation and evaporation rates that are delayed by comparison with temperature increases. There is an “El Nino-like” shift in precipitation and an overall increase in the interannual variability of precipitation. The effect of the aerosol forcing is again primarily to delay and counteract the GHG-induced increase. Decreases in soil moisture are common but regionally dependent and interannual variability changes show considerable structure. Snow cover and sea-ice retreat. A PNA-like anomaly in mean sea-level pressure with an enhanced Aleutian low in northern winter is associated with the tropical shift in precipitation regime. The interannual variability of mean sea-level pressure generally decreases with largest decreases in the tropical Indian ocean region. Changes to the ocean thermal structure are associated with a spin-down of the Atlantic thermohaline circulation together with a decrease in its variability. The effect of aerosol forcing, although modest, differs from that for most other quantities in that it does not act primarily to counteract the GHG forcing effect. The barotropic stream function in the ocean exhibits modest change in the north Pacific but accelerating changes in much of the Southern Ocean and particularly in the north Atlantic where the gyre spins down in conjunction with the decrease in the thermohaline circulation. The results differ in non-trivial ways from earlier equilibrium 2 × CO₂ results with the CCCma model as a consequence of the coupling to a fully three-dimensional ocean model and the evolving nature of the forcing. Received: 24 September 1998 / Accepted: 8 October 1999     

SROCC:海洋热含量变化评估

工业革命以来,大气中温室气体不断增加,驱动了全球变暖。IPCC第五次评估报告(AR5)指出,人类排放的温室气体导致的地球系统能量增加中90%以上都被海洋吸收,使得海洋增暖,海洋热含量增加。IPCC最新发布的《气候变化中的海洋和冰冻圈特别报告》(SROCC)发现：自1970年以来,几乎确定海洋上层2000 m在持续增暖。1993—2017年间的增暖速率至少为1969—1993年的2倍,体现出显著的变暖增强趋势。此外,在20世纪90年代以后,2000 m以下的深海也已观测到了变暖信号,尤其是在南大洋(30°S以南)。在1970—2017年间,南大洋上层2000 m储存了全球海洋约35%~43%的热量,在2005—2017年期间增加到45%~62%。基于耦合气候模型预估,几乎可确定海洋将在21世纪持续增暖,2018—2100年间海洋热含量上升幅度可能是1970—2017年间的5~7倍(RCP8.5情景)或2~4倍(RCP2.6情景)。变暖导致的热膨胀效应贡献了1993年以来全球海平面上升的约43%。     

Relative roles of dynamic and thermodynamic processes in causing positive and negative global mean SST trends during the past 100 years

Global mean surface temperature (GMST) during 1910–2012 experienced four alternated rapid warming and warming hiatus phases. Such a temporal variation is primarily determined by global mean sea surface temperature (SST) component. The relative roles of ocean dynamic and thermodynamic processes in causing such global mean SST variations are investigated, using two methods. The first method is ocean mixed layer heat budget analysis. The budget diagnosis result shows that the thermodynamic processes dominate in the rapid warming phases, while the ocean dynamics dominate during the hiatus phases. The second method relies on the diagnosis of a simple equilibrium state model. This model captures well the horizontal distribution of SST difference between two warmer and cooler equilibrium states during either the rapid warming or hiatus phases. It is found that the SST difference during the rapid warming phases is primarily controlled by the increase of downward longwave radiation as both column integrated water vapor and CO₂ increase during the phases. During the hiatus phases, the water vapor induced greenhouse effect offsets the CO₂ effect, and the SST cooling tendency is primarily determined by the ocean dynamics over the Southern Ocean and tropical Pacific. The SST pattern associated with the Interdecadal Pacific Oscillation (IPO) might be responsible for the remote and local ocean dynamic responses through induced wind change.     

Greenhouse-gas versus aerosol forcing and African climate response

There are many indicators that human activity may change climate conditions all around the globe through emissions of greenhouse gases. In addition, aerosol particles are emitted from various natural and anthropogenic sources. One important source of aerosols arises from biomass burning, particularly in low latitudes where shifting cultivation and land degradation lead to enhanced aerosol burden. In this study the counteracting effects of greenhouse gases and aerosols on African climate are compared using climate model experiments with fully interactive aerosols from different sources. The consideration of aerosol emissions induces a remarkable decrease in short-wave solar irradiation near the surface, especially in winter and autumn in tropical West Africa and the Congo Basin where biomass burning is mainly prevailing. This directly leads to a modification of the surface energy budget with reduced sensible heat fluxes. As a consequence, temperature decreases, compensating the strong warming signal due to enhanced trace gas concentrations. While precipitation in tropical Africa is less sensitive to the greenhouse warming, it tends to decrease, if the effect of aerosols from biomass burning is taken into account. This is partly due to the local impact of enhanced aerosol burden and partly to modifications of the large-scale monsoon circulation in the lower troposphere, usually lagging behind the season with maximum aerosol emissions. In the model equilibrium experiments, the greenhouse gas impact on temperature stands out from internal variability at various time scales from daily to decadaland the same holds for precipitation under the additional aerosol forcing. Greenhouse gases and aerosols exhibit an opposite effect on daily temperature extremes, resulting in an compensation of the individual responses under the combined forcing. In terms of precipitation, daily extreme events tend to be reduced under aerosol forcing, particularly over the tropical Atlantic and the Congo basin. These results suggest that the simulation of the multiple aerosol effects from anthropogenic sources represents an important factor in tropical climate change, hence, requiring more attention in climate modelling attempts.     

Responses of East Asian summer monsoon to historical SST and atmospheric forcing during 1950–2000

The East Asian summer monsoon (EASM) circulation and summer rainfall over East China have experienced large decadal changes during the latter half of the 20th century. To investigate the potential causes behind these changes, a series of simulations using the national center for atmospheric research (NCAR) community atmospheric model version 3 (CAM3) and the geophysical fluid dynamics laboratory (GFDL) atmospheric model version 2.1 (AM2.1) are analyzed. These simulations are forced separately with different historical forcing, namely tropical sea surface temperature (SSTs), global SSTs, greenhouse gases plus aerosols, and a combination of global SSTs and greenhouse gases plus aerosols. This study focuses on the relative roles of these individual forcings in causing the observed monsoon and rainfall changes over East Asia during 1950–2000. The simulations from both models show that the SST forcing, primarily from the Tropics, is able to induce most of the observed weakening of the EASM circulation, while the greenhouse gas plus (direct) aerosol forcing increases the land-sea thermal contrast and thus enhances the EASM circulation. The results suggest that the recent warming in the Tropics, especially the warming associated with the tropical interdecadal variability centered over the central and eastern Pacific, is a primary cause for the weakening of the EASM since the late 1970s. However, a realistic simulation of the relatively small-scale rainfall change pattern over East China remains a challenge for the global models.     

全球增暖对ENSO影响的数值模拟研究

利用日本东京大学气候系统研究所、日本环境研究所和日本地球环境研究中心联合开发的海气耦合模式MIROC3.2,研究了全球变暖对ENSO年际变率的影响。该模式较好地模拟了ENSO循环的不同阶段表层和次表层海水温度变化,海表温度最大振幅出现在120°W以东,与观测一致,表明模式可以较好反映热带地区大气、海洋的动力、热力特征。研究还比较了控制试验和CO2浓度年增长1%的瞬时试验,结果表明,在全球变暖的大环境下ENSO事件发生频率没有显著变化,但ENSO事件强度增大,年际变率变大;热带太平洋呈现整体增暖趋势,表层温度尤其是热带中太平洋地区温度升高显著。敏感性分析表明,年际ENSO变率的振幅增大的主要贡献来自于海洋。海水增温导致热带太平洋海温垂直梯度增大,在热带西太平洋海温垂直温度梯度变化最为明显;次表层海温对单位大气风应力变化的响应大于表层海温响应。当这种响应与热带太平洋赤道地区径向温度梯度变化的共同作用导致温室效应下ENSO振幅增大。