全球气候变暖:浅谈从AR5到AR6的认知进展

自政府间气候变化专门委员会（IPCC）第五次评估报告（AR5）发布以来,国际科学界在气候系统变化领域取得显著进展,有关气候变化的科学认识不断深入。IPCC第六次评估报告（AR6）第一工作组（WGI）报告对这些科学进展和最新认识作了综合评估。温度是全球变化最直接的指示器。本文从温度变化视角,对从AR5到AR6的科学进展进行了梳理和简要评述,主要聚焦观测的变化、归因以及未来预估三个方面。与AR5相比,AR6以更强有力的证据进一步确证了近百年全球气候变暖的客观事实,人类活动对气候变暖影响的信号更为清晰,未来变暖幅度取决于温室气体减排力度。     

气候变化——人类面临的机遇和挑战

根据联合国环境规划署（UNEP）和世界气象组织共同组建的政府间气候变化委员会（IPCC），组织全世界几百名著名科学家的科学评估报告指出“过去100年中全球气候总的趋势是变暖的，全球地面气温上升了0．3℃到0．6℃，如果人类不有效的控制温室气体的排放，全球气候将持续变暖，在未来40年至50年内全球平均温度如每10年上升0．2℃，[第一段]     

IPCC成立以来对温度升高的评估与预估

自1990年开始,政府间气候变化专门委员会（IPCC）已经陆续出版了4次评估报告和1次补充报告。本文回顾了近20a对全球及中国温度升高值的评估及预估的变化。全球平均温度的资料来源于IPCC第一工作组4次评估报告,中国的资料则主要来自与IPCC 4次报告大致对应时期的有关研究。     

青藏高原三江源地区近60a气候与极端气候变化特征分析

青藏高原三江源地区正在面临着以"变暖变湿"为主的气候变化，是气候变化的显著区与敏感区。基于中国气象局位于三江源地区20个地面台站的气温、降水数据以及HadCRUT4（Climatic Research Unit land-surface air temperature-4 dataset and the Hadley Centre sea-surface temperature dataset，Hadley Centre，UK）气温、PREC（Precipitation Reconstruction，National Oceanic and Atmospheric Administration，USA）降水资料，从气候要素空间格局、极端气候指标以及区域-全球平均多年变化对比等3个方面系统总结了三江源地区1961-2019年气候和极端气候变化的特征。结果显示，三江源区域在过去近60 a里平均增暖速率为0.37℃/（10 a），是全球平均水平（0.16℃/（10 a））的2倍以上，同时大幅高于全球同纬度（0.19℃/（10 a））及中国区域（0.28℃/（10 a））。在全球变暖背景下，三江源地区大部分极端气候指标上升，其中以夜间最低气温的上升（0.55℃/（10 a））最为显著，且极端高温事件的出现频率上升，区域日温差减小、气温变化极端性增强。三江源近60 a温湿气候态的空间格局为沿西北-东南方向的正温湿梯度，其变化趋势存在自西向东速率上升的暖湿化空间分异特征。本文的研究结论进一步揭示了三江源地区近60 a气候变化与极端气候的时空格局，为三江源地区气候系统和生态系统的脆弱性研究以及未来气候变化预估提供了科学依据，同时也为气候变化敏感的高寒地区对全球变暖的响应研究提供了对比案例。     

气象风云图

IPCC全球温度预测：基本准确 1990年,政府间气候变化专门委员会（IPCC）在发布第一个气候变化评估报告时,给出了1990—2030年全球平均温度的预测（图中蓝色线）。     

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。     

将全球变暖限制在1.5℃

IPCC发布新的评估报告,全名为《IPCC在加强全球应对气候变化威胁、实现可持续发展和努力消除贫困的背景下,关于全球升温高于工业化前水平1.5°C的影响和相关全球温室气体排放路径的全球升温1.5℃特别报告》。报告指出,将全球变暖限制在1.5℃需要社会各方进行快速、深远和前所未有的变革。     

IPCC 1.5℃特别报告发布,温室气体减排新时代的标志

2018年10月8日,IPCC发布了《IPCC全球升温1.5℃特别报告》^[1]。2016年,联合国气候变化框架公约（UNFCCC）在通过《巴黎协定》时发出的邀请,IPCC于2016年10月份决定开始编写这份报告。2017年初,IPCC选择了来自40个国家的91位作者,启动了报告的编写。这份报告的全名为《IPCC在加强全球应对气候变化威胁、实现可持续发展和努力消除贫困的背景下,关于全球升温高于工业化前水平1.5℃的影响和相关全球温室气体排放路径的全球升温1.5℃特别报告》。     

人类活动对20世纪中国西北地区气候变化影响检测和21世纪预测

使用各国政府间气候变化专门委员会(IPCC)第一工作组(WG1)2001年科学评估报告中给出的7个全球气候系统模式(CCC、CCSR、CSIRO、DKRZ、GFDL、HADL、NCAR),对20世纪中国西北地区气候变化作检测表明,从观测计算得到的近百年中国西北地区气候变暖0.75℃和近50年气候变暖0.88℃,很可能与人类活动造成大气中温室气体浓度增加以及硫化物气溶胶增加有联系.所有模式的控制试验没有表现出明显的增暖趋势,但是,根据20世纪的排放,所有模式模拟出温室气体增加或温室气体与硫化物气溶胶增加,造成西北地区变暖平均为0.34～1.57℃/100 a和0.90～1.86℃/50 a.所有模式对21世纪中国西北地区气候变化的计算表明,21世纪由于人类活动排放温室气体增加,以及温室气体和硫化物气溶胶增加,西北地区气温将可能平均升高2.79～4.50℃/100a.对21世纪未来降水变化的分析表明,由于温室气体增加,以及由于温室气体和硫化物气溶胶增加,未来西北地区降水将可能增加48～60 mm/100a.由于全球气候模式在模拟区域尺度气候变化上存在较大的不确定性,以及人类活动排放的多样性,因此,对未来的预测展望存在不确定性.     

IPCC三个特别报告正在准备中

正自IPCC~①第五次科学评估报告3个工作组的报告~([1-3])于2013—2014年先后发表以来,到2022年发表第六次评估报告前,IPCC准备撰写和发布三个特别报告,以进一步评估当前的几个热点问题,即:第一个特别报告是有关全球变暖高于工业化前水平1.5℃的影响以及相应的全球温室气体排放路径(简称SR1.5);第二个特别报告是有关气候变化、沙漠化、土地退化、可持续土地利用管理、粮食安全和陆地生态系统温室气体通量;第三个特别报告是关     

About modern climate state and suggestions on actions to counteract climate changes

Over the last 20 years the mankind has been concerned about the problem of anthropogenic climate warming influencing noticeably many physical and biological systems and processes. Both negative and positive consequences are observed herein. Mankind attempts to take actions against climate warming using the efforts to control greenhouse gas emissions (first of all CO₂), however, these attempts give little results. The Intergovernmental Panel on Climate Change (IPCC) has been thoroughly assessing climate changes and their consequences over 20 years. It was noted that average global temperature over the last 100 years increased by 0.74°C. In the last report of the IPCC (2007), it was shown that to prevent warming by 2050 (at acceptable level) the CO₂ global emission should be cut by 50–85%, what is technologically impossible. Other methods are suggested to stabilize a modern climate, in particular, to introduce fine-disperse aerosol particles into the lower stratosphere. It is noteworthy that the Meeting of Presidents (and their Representatives) of Academies of Sciences from 13 countries to prepare a Statement for the G8 Summit in Tokyo in 2007, considered in detail the author’s proposal and insert a paragraph, where the research of that method (including holding a conference) was approved.     

气候变化科学的最新进展—IPCC第四次评估综合报告解析

政府间气候变化专门委员会（IPCC）第四次评估报告综合报告于2007年11月17日在西班牙正式发布。综合报告将温室气体排放、大气温室气体浓度与地球表面温度直接联系起来,综合评估了气候变化科学、气候变化的影响和应对措施的最新研究进展。综合报告指出：控制温室气体排放量的行动刻不容缓;能否减小全球变暖所带来的负面影响,将在很大程度上取决于人类在今后二三十年中在削减温室气体排放方面所作的努力和投资。这对国际社会和各国政府制定经济社会发展政策,适应和减缓气候变化有一定的指导和促进作用。     

On Orderly Adaptation to Global Warming

Global warming during the last century has been a well-known fact. Despite arguments and uncertainties in explanations, most scientists agree that this century-scale warming trend is attributable to human activities. According to the recent assessment report of the Intergovernmental Panel on Climate Change （IPCC, 2007） based on worldwide scientific results,     

IPCC第五次评估报告第一工作组主要结论对《联合国气候变化框架公约》进程的影响分析

IPCC评估报告对国际气候变化谈判进程有重要影响,目前正在陆续发布的第五次评估报告已明确作为气候变化新协议谈判的重要信息来源,对讨论2020年后应对气候变化国际合作机制的影响不容忽视。最先发布的第一工作组评估报告基于新的科学观测事实、更为完善的归因分析和气候系统模式模拟结果,进一步确认了气候变暖的事实,发现了人类活动与全球温升之间因果关系的新证据,以及温室气体累积排放与温升响应之间的定量联系。本文通过分析其中一些关键结论可能的政策含义,探讨了这些关键结论对目前国际气候变化谈判进程和新协议等相关问题的可能影响,探讨了科学信息在气候变化决策过程中的作用,以及如何更为科学地理解和利用这些重要结论。     

气候变化影响的最新认知

政府间气候变化专门委员会（IPCC）第二工作组于2007年4月6日正式发布了第四次评估报告,该报告客观、全面而审慎地评估了气候变化已有的和未来的可能影响。现有观测证据表明,人为增暖可能已对许多自然和生物系统产生了可辨别的影响,但由于适应以及非气候因子的作用,许多影响还难以辨别。21世纪中期,某些中纬度和热带干旱地区年平均河流径流量和可用水量会减少10%～30%;如果全球平均温度增幅超过1.5～2.5℃,目前所评估的20%～30%动植物物种可能面临灭绝的风险会增大;从全球角度看,局地平均温度增加1～3℃,预计粮食生产潜力会增加,但若超过这一范围,则会减少。兼顾适应和减缓的措施能够降低气候变化相关风险。     

Prediction Research of Climate Change Trends over North China in the Future 30 Years

A simulation of climate change trends over North China in the past 50 years and future 30 years was performed with the actual greenhouse gas concentration and IPCC SRES B2 scenario concentration by IAP/LASG GOALS 4.0 （Global Ocean-Atmosphere-Land system coupled model）, developed by the State Key Laboratory of Numerical Modelling for Atmospheric Sciences and Geophysical Fluid Dynamics （LASG）, Institute of Atmospheric Physics （IAP）, Chinese Academy of Sciences （CAS）. In order to validate the model, the modern climate during 1951-2000 was first simulated by the GOALS model with the actual greenhouse gas concentration, and the simulation results were compared with observed data. The simulation results basically reproduce the lower temperature from the 1960s to mid-1970s and the warming from the 1980s for the globe and Northern Hemisphere, and better the important cold （1950 1976） and warm （1977-2000） periods in the past 50 years over North China. The correlation coefficient is 0.34 between simulations and observations （significant at a more than 0.05 confidence level）. The range of winter temperature departures for North China is between those for the eastern and western China＇s Mainland. Meanwhile, the summer precipitation trend turning around the 1980s is also successfully simulated. The climate change trends in the future 30 years were simulated with the CO2 concentration under IPCC SRES-B2 emission scenario. The results show that, in the future 30 years, winter temperature will keep a warming trend in North China and increase by about 2.5~C relative to climate mean （1960-1990）. Meanwhile, summer precipitation will obviously increase in North China and decrease in South China, displaying a south-deficit-north-excessive pattern of precipitation.     

1.5℃增暖对全球和区域影响的研究进展

《巴黎协定》明确提出将全球平均升温控制在相对于工业化前水平2℃以内,并努力将其控制在1.5℃以内,以降低气候变化的风险与影响。随后,《联合国气候变化框架公约》（UNFCCC）邀请IPCC筹备关于1.5℃增暖影响及温室气体排放途径的特别报告,为UNFCCC谈判提供科学依据。通过回顾近期发表的一些成果发现,在1.5℃到2℃的不同升温条件下,很多极端天气事件发生的概率将增加。2℃条件下一些易受威胁的系统,如生态系统和农业系统,将承受全球变暖带来的严重后果;海平面明显上升,珊瑚礁锐减,季风降水减弱等影响将进一步加强。同时,不同地区对全球不同程度增暖的响应也存在很大差异。总的说来,相较于2℃增暖而言,将增暖控制在1.5℃以内能进一步减小气候变化影响的风险。然而,要把全球增暖控制在1.5℃内具有极大的挑战性,并且目前对1.5℃增暖的影响认识仍然十分不足。定量分析2℃和1.5℃增暖对不同区域自然和人类系统造成的影响差异,需要更高分辨率的模式以及更多针对2℃和1.5℃增暖影响而设计的专门试验支持。     

Recent Rapid Regional Climate Warming on the Antarctic Peninsula

The Intergovernmental Panel on Climate Change (IPCC) confirmed that mean global warming was 0.6 ± 0.2 °C during the 20th century and cited anthropogenic increases in greenhouse gases as the likely cause of temperature rise in the last 50 years. But this mean value conceals the substantial complexity of observed climate change, which is seasonally- and diurnally-biased, decadally-variable and geographically patchy. In particular, over the last 50 years three high-latitude areas have undergone recent rapid regional (RRR) warming, which was substantially more rapid than the global mean. However, each RRR warming occupies a different climatic regime and may have an entirely different underlying cause. We discuss the significance of RRR warming in one area, the Antarctic Peninsula. Here warming was much more rapid than in the rest of Antarctica where it was not significantly different to the global mean. We highlight climate proxies that appear to show that RRR warming on the Antarctic Peninsula is unprecedented over the last two millennia, and so unlikely to be a natural mode of variability. So while the station records do not indicate a ubiquitous polar amplification of global warming, the RRR warming on the Antarctic Peninsula might be a regional amplification of such warming. This, however, remains unproven since we cannot yet be sure what mechanism leads to such an amplification. We discuss several possible candidate mechanisms: changing oceanographic or changing atmospheric circulation, or a regional air-sea-ice feedback amplifying greenhouse warming. We can show that atmospheric warming and reduction in sea-ice duration coincide in a small area on the west of the Antarctic Peninsula, but here we cannot yet distinguish cause and effect. Thus for the present we cannot determine which process is the probable cause of RRR warming on the Antarctic Peninsula and until the mechanism initiating and sustaining the RRR warming is understood, and is convincingly reproduced in climate models, we lack a sound basis for predicting climate change in this region over the coming century.     

Detection, Causes and Projection of Climate Change over China： An Overview of Recent Progress

This article summarizes the main results and findings of studies conducted by Chinese scientists in the past five years.It is shown that observed climate change in China bears a strong similarity with the global average.The country-averaged annual mean surface air temperature has increased by 1.1℃over the past 50 years and 0.5-0.8℃over the past 100 years,slightly higher than the global temperature increase for the same periods.Northern China and winter have experienced the greatest increases in surface air temperature.Although no significant trend has been found in country-averaged annual precipitation, interdecadal variability and obvious trends on regional scales are detectable,with northwestern China and the mid and lower Yangtze River basin having undergone an obvious increase,and North China a severe drought.Some analyses show that frequency and magnitude of extreme weather and climate events have also undergone significant changes in the past 50 years or so. Studies of the causes of regional climate change through the use of climate models and consideration of various forcings,show that the warming of the last 50 years could possibly be attributed to an increased atmospheric concentration of greenhouse gases,while the temperature change of the first half of the 20th century may be due to solar activity,volcanic eruptions and sea surface temperature change.A significant decline in sunshine duration and solar radiation at the surface in eastern China has been attributed to the increased emission of pollutants. Projections of future climate by models of the NCC(National Climate Center,China Meteorological Administration)and the IAP(Institute of Atmospheric Physics,Chinese Academy of Sciences),as well as 40 models developed overseas,indicate a potential significant warming in China in the 21st century,with the largest warming set to occur in winter months and in northern China.Under varied emission scenarios,the country-averaged annual mean temperature is projected to increase by 1.5-2.1℃by 2020,2.3-3.3℃by 2050, and by 3.9-6.0℃by 2100,in comparison to the 30-year average of 1961 1990.Most models project a 10% 12% increase in annual precipitation in China by 2100,with the trend being particularly evident in Northeast and Northwest China,but with parts of central China probably undergoing a drying trend.Large uncertainty exists in the projection of precipitation,and further studies are needed.Furthermore,anthropogenic climate change will probably lead to a weaker winter monsoon and a stronger summer monsoon in eastern Asia.