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中国气温变化对全球变暖停滞的响应
杜勤勤,, 张明军,, 王圣杰, 车存伟, 邱雪, 马转转
西北师范大学地理与环境科学学院,兰州 730070

作者简介:杜勤勤(1994-), 女, 甘肃庄浪人, 硕士研究生, 主要从事全球变化与可持续发展方面的研究。E-mail: geoduqin@163.com

通讯作者:张明军(1974- ), 男, 甘肃宁县人, 教授, 博士生导师, 中国地理学会会员(S110007775), 主要从事气候变化与生态水文过程方面的研究。E-mail: mjzhang2004@163.com
摘要

1998-2012年出现的全球变暖停滞(global warming hiatus)现象,近年来受到各界的广泛关注。基于中国622个气象站的气温数据,研究了全国及三大自然区气温变化对全球变暖停滞的响应。结果表明:① 1998-2012年间,中国气温变化率为-0.221 ℃/10 a,较1960-1998年增温率下降0.427 ℃/10 a,存在同全球变暖停滞类似的增温减缓现象,且减缓程度更明显,其中冬季对中国增温减缓的贡献最大,贡献率为74.13%,夏季最小;② 中国气温变化对全球变暖停滞的响应存在显著的区域差异,从不同自然区看,1998-2012年东部季风区和西北干旱区降温显著,其中东部季风区为中国最强降温区,为全国增温减缓贡献了53.79%,并且具有显著的季节依赖性,减缓期冬季气温下降了0.896 ℃/10 a,而夏季上升了0.134 ℃/10 a。青藏高寒区1998-2012年增温率达0.204 ℃/10 a,对全球变暖停滞的响应并不显著;③ 中国增温减缓可能受太平洋年代际振荡(PDO)负相位、太阳黑子数与太阳总辐照减小等因素的影响;④ 1998-2012年中国虽出现增温减缓现象,但2012年之后气温快速升高,且从周期变化看,未来几年可能持续升温。

关键词: 全球变暖停滞; 中国; 三大自然区; 气温;
Changes in air temperature of China in response to global warming hiatus
DU Qinqin,, ZHANG Mingjun,, WANG Shengjie, CHE Cunwei, QIU Xue, MA Zhuanzhuan
College of Geography and Environmental Science, Northwest Normal University, Lanzhou 730070, China
Abstract

The global warming hiatus during 1998-2012 has aroused a great public interest in past several years. Based on the air temperature at 622 meteorological stations in China, the response of temperature to global warming hiatus was analyzed on national and regional scales. The main results were as follows: (1) The trend magnitude of air temperature in China was -0.221 ℃/10 a during 1998-2012, which was lower than the long-term trend during 1960-1998 by 0.427 ℃/10 a. There was a warming hiatus in China that was more obvious than the global mean. Winter played a dominant role (contribution rate was 74.13%) in the nationwide warming hiatus, and the contribution of summer was the least among the four seasons. (2) The warming hiatus was spatial incoherent in different climate backgrounds in China. Among the three natural zones in China (the monsoon region of eastern China, the arid region of northwestern China and the high frigid region of Tibetan Plateau), there was a significant cooling in the eastern and northwestern China, especially the eastern China with a contribution rate of 53.79%. In the eastern China, the trend magnitudes were 0.896 ℃/10 a in winter and 0.134 ℃/10 a in summer, respectively. In the Tibetan Plateau, the air temperature has increased by 0.204 ℃/10 a without significant warming hiatus. (3) The warming hiatus in China may be associated with the negative phase of PDO as well as the reduction of sunspot numbers and total solar radiation. (4) Although warming hiatus occurred in China during 1998-2012, the air temperature has rapidly increased after 2012 and is likely to be continuously warming in the next few years.

Keyword: global warming hiatus; China; three natural zones; temperature;
1 引言

政府间气候变化专门委员会(IPCC)第五次评估报告[1]指出,1901-2012年全球平均地表温度升高0.89 ℃(0.69 ℃~1.08 ℃),此间几乎所有地区均经历了显著的变暖。气候变暖引起海平面上升、海洋酸化、冰冻圈退缩、水循环紊乱(水短缺等)、极端事件频发、生物多样性受损等 诸多问题,成为影响自然生态系统和社会经济系统的重要因素之一[2,3,4]。然而,2006年澳大利亚詹姆斯—库克大学(James Cook University)的Carter[5]发现全球变暖出现停滞现象(global warming hiatus),在这之后引起社会各界就全球变暖停滞到底是否存在及其形成机制的激烈争论[6,7,8,9,10,11,12,13,14,15,16,17]

Knight等[6]和Kerr等[7]基于全球实测气温数据和再分析资料对1998-2012年及其前期全球气温变化进行对比研究,证实气候变暖停滞这一现象确实存在。IPCC第五次评估报告[1]也明确指出:过去15年(1998-2012年)以来,全球地表温度的线性增暖趋势较之前的30~60年显著减缓,约为1951-2012年增暖幅度的1/3~1/2。然而,也有一些学者对此持反对意见[13,14,15],如Karl等[14]提出,1998-2012年全球变暖停滞是由资料问题所致,其用订正过的气温资料得出全球平均地表气温变化并未出现变暖停滞,资料经过订正后,1951-2012年与1998-2012年气温变化趋势的差异显著减小,2000-2014年与1950-1999年气温变化趋势变得非常接近(尤其在海洋地区)。Huang等[15]发现北极地区近年来升温显著,2000年以来,大约是全球升温速度的6倍,而先前的全球平均表面温度计算中没有考虑北极地区温度的变化,通过北极气温重建证明全球气候变暖并未停滞。还有一种观点认为,地球上小波动变冷或变暖减缓经常发生,但是近百年来整体变暖趋势毋庸置疑[16]。诚然如此,但对于1998-2012年气候变暖是否出现停滞应该得到充分说明和证实。

目前关于全球气候变暖以及变暖停滞的研究大多数基于再分析数据展开,再分析数据虽然有利于大尺度研究,但精度上远没有实测数据可靠,这可能也是为什么大多数气候模式难以模拟出全球变暖停滞的重要原因[14]。再者,不同区域温度变化存在显著差异。鉴于此,本文将中国作为研究区域,基于实测气温数据,采用线性倾向估计、小波分析等方法对全球变暖停滞期中国气温变化趋势进行分析,由于中国地域辽阔,区域自然地理环境复杂多样,下垫面性质存在显著差异(图1),本文还研究了中国不同自然区气温变化对全球变暖停滞的响应。根据中国综合自然地理区划[18],可将全国依据地形轮廓、构造运动、土壤植被、外营力等因素划分为东部季风区、西北干旱区和青藏高寒区三大自然区。

图1 中国气象站点地理位置及分区 Fig. 1 Location of meteorological stations and divisions in China

本文可为全球变暖停滞是否真实存在提供证据,同时对认识不同下垫面条件下的气候变暖态势具有重要科学意义。气温是影响生物圈、人类活动的重要因素之一,气温变化定量分析对指导人类社会的生产、生活实践也具有重要意义[19]

2 数据来源与研究方法
2.1 数据来源

气温数据来自中国气象数据网(http://data.cma.cn),共选用了1960-2016年间连续气象观测记录大于42年的622个气象站(港澳台地区资料暂缺)逐月平均气温数据进行分析,这些气象站大多数为国家基准气候站和基本气象站,少数为一般气象站(图1)。对于极少数站点个别年份缺测的情况,采用线性回归方法插补得到,以确保气温数据的完整性与连续性。此外,太平洋年代际振荡(Pacific Decadal Oscillation, PDO)指数来自http://research.jisao.washington.edu/pdo/,时间序列为1900-2016年;太阳黑子数据来自美国国家海洋和大气管理局(http://www.noaa.gov/),时间序列为1700-2016年;太阳总辐照数据使用LASP/LISIRD网站(http://lasp.colorado.edu/lisird/tsi/historical_tsi.html)提供的历史重构数据,时间序列为1610-2016年。

2.2 研究方法

2.2.1 全国与三大自然区平均气温序列的建立 在建立全国与三大自然区平均气温序列时,采用Jones[20]提出的计算区域平均气温时间序列的方法:① 根据逐月气温资料,计算每个气象站点的全年及四季的平均气温序列,四季的划分为:3月-5月为春季,6月-8月为夏季,9月-11月为秋季,12月-翌年2月为冬季;② 计算各个气象站点的气温距平,计算气温距平的标准期为1971-2000年;③ 将全国按经纬度划分为2°×2°的网格,把每个网格内的所有站点的气温距平做算数平均,得到每个网格的气温距平值;④ 按网格的面积求出所有网格气温距平的加权平均值,计算全部网格面积加权平均值的公式为:

Y k = i = 1 m ( cos θ i ) × Y ik i = 1 m cos θ i (1)

式中:Yk为第k年区域平均值,i=1, 2, 3…, mm为网格数);Yik为第i个网格中第k年的平均值;θi为第i个网格中心的纬度。

2.2.2 不同区域和季节对全国气温变化速率的贡献率的计算方法 为量化三大自然区对全国气温变化速率的贡献,选用季明霞[21]的方法来计算各个区域相对于全国陆地平均气温增温速率的贡献率X(i),具体公式为:

X ( i ) = A ( i ) × S ( i ) i = 1 N A ( i ) × S ( i ) × 100 % (2)

式中:A(i)是某一时期第i个区域平均的气温线性趋势系数;S(i)是第i个区域陆地面积占全国陆地面积的百分比,根据中国综合自然地理区划[18],东部季风区、西北干旱区和青藏高寒区占全国陆地面积的百分比分别为45%、30%和25%。

同理,不同区域对全国陆地增温减缓的贡献 Δ X ( i ) 为:

Δ X ( i ) = A 2 ( i ) - A 1 ( i ) × S ( i ) i = 1 N A 2 ( i ) - A 1 ( i ) × S ( i ) × 100 % (3)

式中: A 1 ( i ) 是前一个时期(如全国变暖加速期1960-1998年)区域平均的气温线性趋势系数; A 2 ( i ) 是后一个时期(如全国增温减缓期1998-2012年)区域平均的气温线性趋势系数。

不同季节对于全国年平均气温变化速率的贡献 Y ( i ) 为:

Y ( i ) = B ( k ) × 1 / T i = 1 N B ( k ) × 1 / T × 100 % (4)

式中: B ( k ) 是第k个季节区域平均的气温线性趋势系数;T = 4,代表4个季节。

不同季节对于全国增温减缓的贡献 Z ( i ) 为:

Δ Y ( i ) = B 2 ( k ) - B 1 ( k ) × 1 / T i = 1 N B 2 ( k ) - B 1 ( k ) × 1 / T × 100 % (5)

式中: B 1 ( k ) 是前一个时期(例如全国变暖加速期1960-1998年)第k个季节区域平均的气温线性趋势系数; B 2 ( k ) 是后一个时期(例如全国变暖减缓期1998-2012年)区域平均的气温线性趋势系数。

本文为了量化不同区域和季节对中国增温减缓的贡献,将变暖停滞期(1998-2012年)[1]之前的时期1960-1998年定义为变暖加速期,便于计算分析。

2.2.3 小波分析 小波分析方法在气候、水文等领域广泛应用,本文利用气候学研究中常用的Morlet小波分析对气温进行周期分析,并用小波方差确定气温周期和主周期。

3 结果与分析
3.1 中国气温变化对全球变暖停滞的响应

3.1.1 年际变化 1998-2012年全球(陆地和海洋)增温速率为0.04 ℃/10 a,与1951-2012年0.117 ℃/10 a相比,变暖速率显著减缓(表1),但2000年之后,全球表面气温快速上升。由此可见,1998-2012年间的变暖停滞十分短暂。且近15年变暖停滞期,地表气温的时空分布在全球范围内并不一致[22],例如,全球海洋表面气温较1951-2012年增温率略有下降,而全球陆地表面气温下降趋势更为明显。

表1 全球[1]和中国不同时段平均气温的线性变化率 Tab. 1 Trend magnitude of average air temperature across the globe[1] and China during different periods

从全球陆地、北半球陆地以及中国平均气温距平序列看(图2),1980年以来,4套数据集显示全球与北半球陆地平均气温均呈上升趋势,其中1980-1998年是气温增长过程中的一个加速期。1998-2012年全球陆地增温速率为0.039 ℃/10 a,约为1951-2012年的1/5,北半球亦是如此。就中国区域而言(表1,图2c),1960-2016年气温整体呈显著上升趋势,增温速率为0.274 ℃/10 a,57年共上升1.56 ℃,20世纪80年代开始,气温快速上升且在1998年达到峰值,随后波动下降直到2012年跌至谷值,此阶段内1998-2012年降温趋势(-0.221 ℃/10 a)显著。Karl等[14]研究发现,21世纪后,中纬度陆地出现了显著降温趋势。可见,1998-2012年中国存在同全球陆地、北半球陆地一致的增温减缓现象。在全球、北半球和中国区域均可发现:2012年之后气温快速上升,此次增温减缓十分短暂,且1998-2012年平均气温高于多年平均值,气温并没有激烈下降。尽管如此,1998-2012年增温减缓仍不容忽视,因为这15年间温室气体浓度不断增加,但是气温并未表现出明显的线性增暖趋势,且众多模式也未能模拟出近十几年的变暖停滞[11],其内在机制有待进一步研究。

图2 全球、北半球和中国的陆地平均气温距平变化
注:全球和北半球数据来自CRUTEM4[23]、NCEI/NOAA[14]、GISS[24]和Berkeley Earth (http://berkeleyearth.lbl.gov/regions/global-land),其中未订正的NOAA数据来自于NCEI[14],计算距平的标准期为1961-1990年;阴影部分表示1998-2012年全球变暖停滞期。
Fig. 2 Changes in anomalies of terrestrial average air temperature across the globe, the Northern Hemisphere and China

3.1.2 季节变化 已有研究表明:1998年以来全球地表气温在冬季呈下降趋势,在夏季则呈上升趋势[25];在北半球,变暖停滞在冬季比夏季更为明显[22, 25]。在中国,增温减缓期冬季气温下降显著(图3),具体表现在:1998-2012年冬季气温变化率为-0.826 ℃/10 a,较1960-2012年增温速率下降了1.18 ℃/10 a,对中国增温减缓的贡献率为74.13%(表2);春、秋季呈不显著的降温趋势,气温变化率分别为-0.198 ℃/10 a、-0.041 ℃/10 a,对中国增温减缓的贡献率分别为19.16%和13.29%;夏季呈升温趋势,增温速率达0.198 ℃/10 a,较1960-2012年稍有上升,更比变暖加速期1960-1998年高出0.117 ℃/10 a,对全国增温减缓的贡献率为-6.59%,由此可见,夏季气温增长并未减缓。整体来看(图3),1998年之前,冬季增温速率在四季中最快,1998年之后,冬季增温速率急剧下降,前后反差较大。另外,无论是变暖加速期还是变暖停滞期,夏季一直以较为稳定的速率增温。2000年之后,冬季除外,春、夏、秋季均呈增温态势。

图3 不同时段中国四季平均气温的线性变化率(误差线表示90%的置信区间) Fig. 3 Trend magnitude of average air temperature in China for each season during different periods (Error bars denote the 90% confidence interval.)

表2 不同时段中国气温变化的季节贡献率 Tab. 2 Seasonal contribution proportion to air temperature change of China during different periods

3.1.3 周期变化 图4为中国平均气温的小波变换系数实部图和小波方差图,实部图中信号的强弱通过不同颜色的深浅来表示。中国气温变化存在6 a、12 a、29 a左右的振荡周期,其中12 a和29 a尺度周期具有全域性,贯穿整个时间序列(图4a);1970年开始出现6 a左右的振荡周期,2010年消失。小波方差图显示12 a周期为第一主周期(图4b),对全国气温影响显著。增温减缓期间气温变化经历了低温—高温—低温—高温—低温4个完整的冷暖交替过程,此间存在 6 a、12 a、29 a左右的振荡周期,其中12 a、29 a左右的振荡周期一直明显。2016年气温处于暖期,预计未来几年全国将持续升温。

图4 1960-2016年中国平均气温的小波分析结果 Fig. 4 Wavelet analysis of average air temperature in China during 1960-2016

3.1.4 空间变化 (1)1960-2012年间,全国各地普遍呈变暖态势(图5a),其中有95%(595个)的站点呈显著增温趋势,具体表现在:中国北部及青藏高原地区升温速率较快,东南部地区升温相对较慢。全国呈降温趋势的站点仅占5%(12个站点,通过0.05显著性检验的有6个),其中有6个站点分布在云南和四川等地。从季节尺度看(图5b~5e),冬季全国大部分地区升温较快,仅有东部季风区南部升温较慢,有一半的站点未通过0.05的显著性检验;春、秋季气温变化与全年较为相似;夏季全国站点升温速率普遍较小,其中有168个站点降温,主要集中在黄河流域和长江流域中下游区域。

图5 1960-2012年中国全年与季节平均气温线性变化率的空间分布 Fig. 5 Spatial distribution of trend magnitude of annual/seasonal average air temperature in China during 1960-2012

(2)1998-2012年间,中国全年有78.3%(487个)的站点呈降温趋势(图6a),通过0.05显著性检验的占25.1%(156个),仅有21.7%(135个)的站点显示升温。其中呈降温趋势的站点主要分布在西北干旱区和东部季风区(云南大部分地区呈增温趋势),呈显著降温趋势的站点主要集中在西北干旱区和东部季风区交界处。青藏高寒区80%的站点呈升温趋势,呈降温趋势的站点仅占20%。从季节尺度看(图6b~6e),冬季大部分地区呈降温趋势,仅青藏高寒区和云南部分地区呈增温趋势;夏季70.3%的站点表现为显著增温,仅有29.7%的站点呈降温趋势。

图6 1998-2012年中国全年与季节平均气温线性变化率的空间分布 Fig. 6 Spatial distribution of trend magnitude of annual/seasonal average air temperature in China during 1998-2012

(3)2000年之后,全国有71.5%(445个)的站点呈增温趋势(图7a),其中显著增温的站点占17.5%(109个),集中分布在青藏高原和云南地区。有28.5%(177个)的站点呈降温趋势,主要分布在东部季风区、西北干旱区的西部地区和东北部地区。从不同季节看(图7b~7e),气温变化差异较大:冬季有77.8%(484个)的站点呈降温趋势,22.2%(138个)的站点呈增温趋势;秋季有58.4%(363个)的站点呈增温趋势,显著增温的占18.2%(113个),21.1%(131个)的站点呈降温趋势,主要分布在东部季风区北部和西北干旱区西部地区;春、夏季青藏高原和云南部分地区增温显著。

图7 2000-2016年中国全年与季节平均气温线性变化率的空间分布 Fig. 7 Spatial distribution of trend magnitude of annual/seasonal average air temperature in China during 2000-2016

3.2 中国三大自然区气温变化对全球变暖停滞的响应

3.2.1 年际变化 将全国与三大自然区不同时段气温变化率(图8)进行对比可发现,三大自然区对全球变暖停滞的响应存在显著差异。整体来看,1960-2016年、1960-1998年和1960-2012年三大自然区均呈显著升温趋势。1998-2012年间,东部季风区和西北干 旱区呈显著降温趋势,且降温速率均超过全国平均水平,其中西北干旱区降温幅度最大(-0.361 ℃/10 a),其次为东部季风区(-0.31 ℃/10 a)。东部季风区对全国增温减缓贡献最大(53.79%),其次为西北干旱区(46.98%),二者对全球变暖停滞响应显著。然而,1998-2012年青藏高寒区增温速率为0.204 ℃/10 a,与1960-1998年相比略有上升,与1960-2012年相比略有下降,不同时间段内气温变化波动不大,但远远大于同期东部季风区和西北干旱区的增温速率,对全国增温减缓的贡献率为-0.77%,该区域并未出现增温减缓现象。段安民等[26]曾指出,在全球变暖的背景下,青藏高原气温与降水加速增长。本文发现不同时段青藏高寒区均以较高的速率升温,1998年之前,气温变化率与东部季风区、西北干旱区之间差异较小,1998年之后,气温变化率远超全国平均水平。尤其2000年之后,增温速率再创新高。

图8 不同时段中国与三大自然区平均气温的线性变化率(误差线表示90%的置信区间) Fig. 8 Trend magnitude of average air temperature in China and three natural zones during different periods (Error bars denote the 90% confidence interval.)

表3 不同时段中国气温变化的区域贡献率 Tab. 3 Regional contribution proportion to air temperature change of China during different periods

3.2.2 季节变化 由上文分析可知,全国增温减缓具有显著的季节差异性,紧接着探讨三大自然区内不同季节的表现。表4给出了三大自然区不同季节、不同时段的气温变化率,东部季风区增温减缓主要体现在冬季气温的变化上,1998-2012年气温下降-0.896 ℃/10 a,夏季相反,升温速率为0.134 ℃/10 a;增温减缓期间西北干旱区冬季气温下降了-1.425 ℃/10 a,夏季气温则上升了0.217 ℃/10 a,春、秋季呈不显著的降温趋势;1998-2012年青藏高寒区夏季升温速率为0.337 ℃/10 a,其次为春季、冬季,而秋季呈微弱的降温趋势。总而言之,全国、东部季风区和西北干旱区均表现为冬季对增温减缓的贡献最大,夏季最小,且西北干旱区是全国冬季降温最强的区域,也是夏季升温最强的区域。此外,1998-2012年青藏高寒区虽未出现增温减缓现象,也表现为夏季升温最快。

表4 中国三大自然区各季节平均气温的线性变化率 Tab. 4 Trend magnitude of seasonal average air temperature for three natural zones in China

3.2.3 周期变化 图9显示了三大自然区1960-2016年平均气温的周期变化特征:东部季风区与全国类似(图9a1、9a2),平均气温主要存在6 a、13 a、29 a左右的振荡周期,其中13 a左右的周期为第一主周期,1960-2016年间一直表现明显,1980年6 a左右的周期开始表现明显,2010年又逐渐消失;西北干旱区存在6 a、12 a、30 a左右的振荡周期,其中12 a左右的周期为主周期,1960-2016年间一直表现明显,6 a左右的周期1980年才出现,2000年之后逐渐消失,期间表现明显(图9b1、9b2);青藏高寒区存在8 a、11 a、23 a、29 a左右的周期变化,其中29 a左右的周期是主周期,11 a与8 a左右的周期交替出现,且11 a年左右的周期于1985年消失,之后8 a左右的周期出现,2000年11 a左右的周期又出现(图9c1、9c2)。

图9 1960-2016年东部季风区(a1、a2)、西北干旱区(b1、b2)与青藏高寒区(c1、c2)平均气温的小波分析结果 Fig. 9 Wavelet analysis of average air temperature in the monsoon region of eastern China (a1 and a2), the arid region of northwestern China (b1 and b2) and the high frigid region of Tibetan Plateau (c1 and c2) during 1960-2016

全球变暖停滞期间,东部季风区气温存在4类时间尺度的周期变化规律,分别为6 a、13 a、20 a和29 a,其中13 a与29 a左右的周期变化较为稳定,此间气温变化速率呈现负—正—负—正的震荡变化,6 a左右的周期于2004年消失;西北干旱区以12 a左右的周期变化为主,此间平均气温呈现负—正—负—正的震荡变化特征;青藏高寒区气温存在13 a、21 a和29 a左右的振荡周期,29 a左右的周期变化一直表现稳定。

3.3 1998-2012年中国增温减缓的可能影响因素分析

3.3.1 太平洋年代际振荡(PDO)的影响 太平洋年代际振荡(PDO)被认为是影响北半球气候变化的重要模态,尤其会直接造成太平洋及其周边区域(包括中国沿海地区)的气候在年代际尺度上发生变化[27],考虑到太平洋对中国巨大的影响作用,下面简要分析PDO与中国气温变化间的关系:这里PDO指数为正值,称PDO正相位;PDO指数为负值,称PDO负相位。图10给出了PDO指数与中国气温距平时间变化序列,从全年尺度看(图10a1、10a2),20世纪70年代末PDO指数由负转正,90年代中期由正转负,其相位经历了负—正—负—正的变化过程。20世纪60年代至70年代末中国气温呈下降趋势,PDO处于负相位期;80年代开始气温迅速上升,PDO处于正相位期;1998年开始气温增长速率大幅度减缓,PDO处于负相位期;2012年开始气温显著上升,PDO处于正相位期。可以发现,中国气温的升高或降低可能受PDO正相位或负相位的调控。1998-2012年期间,PDO处于负相位期,PDO指数与气温呈正相关关系,中国增温减缓可能受PDO负相位的调控,2012年之后,PDO相位由负转正。从季节尺度看(图10b、10c),夏季PDO指数与气温呈负相关关系,PDO正相位期增温幅度不大,PDO负相位期增温幅度较大;冬季PDO指数呈波动上升趋势,正负相位变化不明显。

图10 1900-2016年(a1、a2、a3)与1960-2016年(b1、b2、b3)PDO指数以及中国平均气温距平的变化 Fig. 10 Changes in PDO index and average air temperature anomalies in China during 1900-2016 (a1, a2 and a3) and 1960-2016 (b1, b2 and b3)

根据PDO的正负相位将中国气温分为1960-1976年(PDO负相位期)、1977-1998年(PDO正相位期)和1999-2013年(PDO负相位期)3个时段进行分析。1960-1976年间,青藏高原以及云南南部地区PDO指数与气温呈正相关关系,东北地区PDO指数与气温间负相关关系显著(图11a);1977-1988年间,内蒙古、甘肃、新疆北部及东北地区PDO指数与气温正相关关系显著(图11b);1999-2013年间,东南沿海地区PDO指数与气温间正相关关系显著(图11c)。由此可见,PDO不同相位时对不同区域的可能影响程度也不同。PDO暖位相时,热带中东太平洋异常暖,阿留申低压加强,西风加强,北太平洋中西部偏冷,赤道中东太平洋、北美沿岸和阿拉斯加湾偏暖,会使得大气环流发生变化,PDO负相位时正好相反[28],可能会对中国气温造成影响。

图11 不同时段PDO指数与中国平均气温相关系数的空间分布 Fig. 11 Spatial distribution of correlation coefficient between PDO index and average air temperature in China during different periods

3.3.2 太阳黑子数(SSN)和太阳总辐照(TSI)的影响 全球气候变化与太阳活动之间的关系一直是研究的热点话题[29,30,31],太阳黑子是描述太阳活动最常用的参数之一,黑子数也是观测资料积累时间最长的太阳活动参数[32],已有学者通过分析太阳黑子与气温的关系来揭示太阳活动对气候的影响[33,34]。本文研究发现,1700-2016年太阳黑子数波动变化趋势明显(图12a1)。1960-2016年,太阳黑子数共出现5个峰值年:1968年、1979年、1989年、2000年和2014年,5个谷值年:1964年、1976年、1986年、1996年和2008年;气温出现5个极大值年:1998年、2006年、2007年、2015年和2016年,5个极小值年:1967年、1969年、1970年、1976年和1984年,可以发现,气温极大值和极小值多发生在太阳黑子活动峰谷年前后及1~2 a之内。1998-2012年,太阳黑子数出现一个峰值、一个谷值,经历了高—低的变化过程,整体呈减小趋势,与中国气温变化趋势一致(图12a2)。此外,1998-2012年太阳黑子数与中国气温呈负相关关系(图12a3),说明变暖停滞期间中国气温降低太阳黑子变化可能并不起主导作用。从太阳总辐照的年际变化看(图12b1),20世纪初太阳总辐照快速上升,截至50年代趋于平缓,1960-2016年间呈增加趋势,与中国气温总体变化趋势一致,1998-2012年间太阳总辐照呈减小趋势,可能是造成中国增温减缓的原因之一。

图12 不同时段太阳黑子数、太阳总辐照与中国平均气温距平的变化(a1、a2、b1、b2)以及1998-2012年太阳黑子数、太阳总辐照与中国平均气温距平的相关性(a3、b3) Fig. 12 Changes in sunspot numbers, total solar irradiance and average air temperature anomalies in China (a1, a2, b1 and b2) during different periods and correlation between sunspot numbers, total solar irradiance and average air temperature anomalies in China during 1998-2012 (a3 and b3)

从前面的研究得出:1960-2016年中国气温存在以12a左右为主的周期变化(图4)。太阳黑子数存在十分明显的11a周期变化(图14),二者周期变化十分相似。但从不同时间段看,二者变化并不同步,1960年太阳黑子进入低谷期,1961年气温进入低谷,1970太阳黑子到达峰值,气温即将进入正值期,2010年太阳黑子即将进入高峰期,气温处于负值期,可见中国气温变化滞后于太阳黑子变化,气温可能受太阳黑子变化调控。1998-2012年太阳黑子经历了一个低谷期,中国气温减小趋势明显,2000年之后,太阳黑子进入峰值,而2000年之后,中国气温变化速率快速升高,二者之间有较好的对应关系。

图13 1960-2016年太阳黑子数的小波分析结果 Fig. 13 Wavelet analysis of sunspot numbers during 1960-2016

4 讨论

全球变暖停滞具有明显的区域性和季节性。① 北极地区和中国青藏高寒区在变暖停滞期均表现异常。Huang等[15]发现1998-2012年北极地区增温显著;在中国,本文发现青藏高寒区不存在增温减缓现象,两者之间存在共同之处,但是二者之间的内在联系和差异尚不清楚,在1998-2012年全球陆地降温的背景下,二者为何呈增温趋势?原因也有待探究。② 从不同季节看,冬季气温变化值得关注。在北半球,热带外大陆冬季的地表气温趋势存在着由增暖转变为近10年几近中性甚至变冷的系统性减弱现象[35];在欧亚大陆和美国大部分地区,2009-2010年出现了冬季持续性低温和暴风雪事件,冬季平均气温显著低于气候平均值[36,37];在中国,2004-2005年大部分地区冬季平均气温低于历史平均 值[38],2007-2008年冬季平均气温与多年平均气温相比呈现显著的负异常[39,40,41]。本文发现中国在变暖停滞期冬季降温幅度较大,2000年以来中国全年总体呈升温趋势,但冬季气温下降依旧显著,在今后研究中应更加重视对近十几年不同区域冬季气温剧烈下降内在机制的研究。

截至目前,诸多科学家对全球变暖停滞的可能形成机制进行了探究[17, 25, 42-49],Meehl等[17]和Kosaka等[25]均认为hiatus的出现可能与拉尼娜的状态相关联;Schmidt等[43]认为火山活动和太阳活动引起的辐射变化与自然变率中的厄尔尼诺现象演变的叠加可能是造成hiatus的原因;Dai等[44]认为太平洋年代际变化(IPO)是造成hiatus的重要原因之一;Li等[45]指出北大西洋涛动(NAO)多年代际变化是hiatus形成的一个重要因素;Douville 等[46]和Yao等[47]认为hiatus的形成与PDO有关。结果主要可归纳为两类,一是外强迫,即太阳辐射、火山喷发气溶胶等导致了变暖停滞;二是自然内部变率,其中最主要的是海洋的影响作用。但以往的研究均并未量化二者对变暖停滞的相对贡献,也未阐明各种形成机制之间相互作用的复杂过程。关于1998-2012年中国降温内在机制的研究较少,本文发现1998-2012年间PDO处于负相位期,且太阳黑子数、太阳总辐照均减小,可能会造成中国增温减缓的发生,但PDO对中国气候变化的影响途径和机制仍不明确,PDO活动与太阳活动是什么关系?与其他影响因素之间是什么关系?在未来研究中仍需进一步探究。

此外,本文基于实测气温资料进行分析,能准确地反映中国气温变化趋势,但时间序列仅57年,短时间序列对于研究气候的长期变化仍然不够,使用何种可靠的重构气温资料研究气温长期变化趋势是下一步努力的目标。

5 结论

(1)1998-2012年间,中国气温线性变化率为-0.221 ℃/10 a,较1960-1998年、1960-2012年、1960-2016年分别下降了0.427 ℃/10 a、0.483 ℃/10 a和0.495 ℃/10 a。通过将中国与全球、北半球气温变化对比发现,中国存在同全球变暖停滞类似的增温减缓现象,且减缓程度更明显。从季节尺度看,中国增温减缓主要体现在冬季气温变化上,夏季增温显著;从三大自然区看,西北干旱区和东部季风区降温显著,1998-2012年气温分别下降了-0.361 ℃/10 a和-0.31 ℃/10 a,远远超过同期全国平均水平,对全国增温减缓贡献最大的是东部季风区,贡献率为53.79%。青藏高寒区1998-2012年增温速率为0.204 ℃/10 a,未出现增温减缓现象。

(2)1998-2012年中国气温变化存在6 a、12 a和29 a左右的振荡周期,其中12 a和29 a左右的振荡周期一直明显;东部季风区气温13 a左右的周期变化较为稳定;西北干旱区气温以12 a左右的周期变化为主;青藏高寒区29 a左右的周期变化十分明显。

(3)1998-2012年中国增温减缓可能受PDO负相位的调控、太阳活动减弱等因素的影响,且不同季节受PDO的影响不同。

(4)相较于1960-1998年的迅速增温,1998-2012年中国增温速率显著减缓,但2012年之后,增温速率高达0.17 ℃/10 a,且从周期变化看,未来几年气温将持续升高。

The authors have declared that no competing interests exist.

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Using an inverse statistical model we examine potential response in sea level to the changes in natural and anthropogenic forcings by 2100. With six IPCC radiative forcing scenarios we estimate sea level rise of 0.6-1.6 m, with confidence limits of 0.59 m and 1.8 m. Projected impacts of solar and volcanic radiative forcings account only for, at maximum, 5% of total sea level rise, with anthropogenic greenhouse gasses being the dominant forcing. As alternatives to the IPCC projections, even the most intense century of volcanic forcing from the past 1000 years would result in 10-15 cm potential reduction of sea level rise. Stratospheric injections of SOequivalent to a Pinatubo eruption every 4 years would effectively just delay sea level rise by 12-20 years. A 21st century with the lowest level of solar irradiance over the last 9300 years results in negligible difference to sea level rise.
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[3] Qin Dahe.Climate change science and sustainable development. Progress in Geography, 2014, 33(7): 874-883.
[本文引用:1]
[秦大河. 气候变化科学与人类可持续发展. 地理科学进展, 2014, 33(7): 874-883.]
政府间气候变化专门委员会(IPCC)自2007 年发布第四次评估报告(AR4)以来,新的观测证据进一步证明,全球气候系统变暖是毋庸置疑的事实。2012 年之前的3 个连续10 年的全球地表平均气温,都比1850 年以来任何一个10 年更高,且可能是过去1400 年来最热的30 年。虽然1998-2012 年全球地表增温速率趋缓,但还不能反映出气候变化的长期趋势。1970 年以来海洋在变暖,海洋上层75 m以上的海水温度每10 年升温幅度超过0.11℃;1971-2010 年地球气候系统增加的净能量中,93%被海洋吸收。全球平均海平面上升速率加快,1993-2010 年间高达3.2 mm/年。全球海洋的人为碳库很可能已增加,导致海洋表层水酸化。1971 年以来,全球几乎所有冰川、格陵兰冰盖和南极冰盖的冰量都在损失。其中1979 年以来北极海冰范围以每10 年3.5%~4.1%的速率缩小,同期南极海冰范围以每10 年1.2%~1.8%的速率增大。北半球积雪范围在缩小。20 世纪80 年代初以来,大多数地区的多年冻土温度升高。已在大气和海洋变暖、水循环变化、冰冻圈退缩、海平面上升和极端气候事件的变化中检测到人类活动影响的信号。1750 年以来大气CO<sub>2</sub>浓度的增加是人为辐射强迫增加的主因,导致20 世纪50 年代以来50%以上的全球气候变暖,其信度超过95%。采用CMIP5 模式和典型浓度路径(RCPs),预估本世纪末全球地表平均气温将继续升高,热浪、强降水等极端事件的发生频率将增加,降水将呈现“干者愈干、湿者愈湿”趋势。海洋上层的温度比1986-2005 年间升高0.6~2.0℃,热量将从海表传向深海,并影响大洋环流,2100 年海平面将上升0.26~0.82m。冰冻圈将继续变暖。为控制气候变暖,人类需要减少温室气体排放。如果较工业化之前的温升达到2℃,全球年均经济损失将达到收入的0.2%~2.0%,并造成大范围不可逆的影响,导致死亡、疾病、食品安全、内陆洪涝、农村饮水和灌溉困难等问题,影响人类安全。但如果采取积极行动,2℃的温升目标仍可望达到。为遏制逐渐失控的全球变暖,需全球共同努力减排,以实现人类可持续发展的理想。
[4] Zhao L, Ding R, Moore J C.The High Mountain Asia glacier contribution to sea-level rise from 2000 to 2050. Annals of Glaciology, 2016, 57(71): 223-231.
We estimate all the individual glacier area and volume changes in High Mountain Asia (HMA) by 2050 based on Randolph Glacier Inventory (RGI) version 4.0, using different methods of assessing sensitivity to summer temperatures driven by a regional climate model and the IPCC A1B radiative forcing scenario. A large range of sea-level rise variation comes from varying equilibrium-line altitude (ELA) sensitivity to summer temperatures. This sensitivity and also the glacier mass-balance gradients with elevation have the largest coefficients of variability (amounting to ~50%) among factors examined. Prescribing ELA sensitivities from energy-balance models produces the highest sea-level rise (9.2 mm, or 0.76% of glacier volume a0900091), while the ELA sensitivities estimated from summer temperatures at Chinese meteorological stations and also from 100°x100° gridded temperatures in the Berkeley Earth database produce 3.6 and 3.8 mm, respectively. Different choices of the initial ELA or summer precipitation lead to 15% uncertainties in modelled glacier volume loss. RGI version 4.0 produces 20% lower sea-level rise than version 2.0. More surface mass-balance observations, meteorological data from the glaciated areas, and detailed satellite altimetry data can provide better estimates of sea-level rise in the future.
DOI:10.3189/2016AoG71A049      [本文引用:1]
[5] Carter B. There is a problem with global warming…it stopped in 1998. Telegraph Newspaper,2016(9).
For many years now, human-caused climate change has been viewed as a large and urgent problem. In truth, however, the biggest part of the problem is neither environmental nor scientific, but a self-created political fiasco. Consider the simple fact, drawn from the
[本文引用:1]
[6] Knight J, Kenneby J J, Folland C, et al.Do global temperature trends over the last decade falsify climate predictions? Bulletin of the American Meteorological Society, 2009, 90(8): 22-23.
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[7] Kerr R A.What happened to global warming? Scientists say just wait a bit. Science, 2009, 326(5949): 28-29.
Not Available
DOI:10.1126/science.326_28a      PMID:19797631      [本文引用:2]
[8] Roberts C D, Palmer M D, McNeall D, et al. Quantifying the likelihood of a continued hiatus in global warming. Nature Climate Change, 2015, 5(4): 337-342.
The probability of a hiatus in global warming is calculated, with a 10-year event having a probability of [sim]10%, but a 20-year event less than 1%. The current 15-year event is found to have up to 25% chance of continuing for another 5 years.
DOI:10.1038/nclimate2531      [本文引用:1]
[9] Yan X H, Boyer T, Trenberth K, et al.The global warming hiatus: Slowdown or redistribution? Earth's Future, 2016, 4(11): 472-482.
Global mean surface temperatures (GMST) exhibited a smaller rate of warming during 1998-2013, compared to the warming in the latter half of the 20th Century. Although, not a "true" hiatus in the strict definition of the word, this has been termed the "global warming hiatus" by IPCC (2013). There have been other periods that have also been defined as the "hiatus" depending on the analysis. There are a number of uncertainties and knowledge gaps regarding the "hiatus." This report reviews these issues and also posits insights from a collective set of diverse information that helps us understand what we do and do not know. One salient insight is that the GMST phenomenon is a surface characteristic that does not represent a slowdown in warming of the climate system but rather is an energy redistribution within the oceans. Improved understanding of the ocean distribution and redistribution of heat will help better monitor Earth's energy budget and its consequences. A review of recent scientific publications on the "hiatus" shows the difficulty and complexities in pinpointing the oceanic sink of the "missing heat" from the atmosphere and the upper layer of the oceans, which defines the "hiatus." Advances in "hiatus" research and outlooks (recommendations) are given in this report.
DOI:10.1002/2016EF000417      [本文引用:1]
[10] Medhaug I, Stolpe M B, Fischer E M, et al.Reconciling controversies about the 'global warming hiatus'. Nature, 2017, 545(7652): 41-47.
Between about 1998 and 2012, a time that coincided with political negotiations for preventing climate change, the surface of Earth seemed hardly to warm. This phenomenon, often termed the ‘global warming hiatus’, caused doubt in the public mind about how well anthropogenic climate change and natural variability are understood. Here we show that apparently contradictory conclusions stem from different definitions of ‘hiatus’ and from different datasets. A combination of changes in forcing, uptake of heat by the oceans, natural variability and incomplete observational coverage reconciles models and data. Combined with stronger recent warming trends in newer datasets, we are now more confident than ever that human influence is dominant in long-term warming.
DOI:10.1038/nature22315      PMID:28470193      [本文引用:1]
[11] Wang Shaowu, Luo Yong, Zhao Zongci, et al.Pause for thought. Advances in Climate Change Research, 2014, 10(4): 303-306.
[本文引用:2]
[王绍武, 罗勇, 赵宗慈, . 对变暖停滞的思考. 气候变化研究进展, 2014, 10(4): 303-306.]
正2014年3月Nature Climate Change发表了一个专栏"近来全球变暖的减缓",加上编者按共6篇文章~([1-6])。下面对这些文章中涉及的几个问题做扼要的介绍。1模式的失败Fyfe等~([7])指出,1998 2012年的15年全球平均温度上升(0.05±0.08)℃,而CMIP5的37个模式117个模拟的结果为(0.21±0.03)℃。从稍长一些的时间如1993—2012年20年分析结果也类似。图1给出1993—2012年的观测及模拟结果的比较。图中横坐标为赤道东太平洋海温变化趋势,纵坐标为全球平均温度变化趋势,红点为HadCRUT4观测值,黑色圆圈为不同模式的不同积分,黑色椭圆为5%~
[12] Zhao Zongci, Luo Yong, Huang Jianbin.Debate on global warming "hiatus". Advances in Climate Change Research, 2016, 12(6): 571-574.
[本文引用:1]
[赵宗慈, 罗勇, 黄建斌. 围绕全球变暖“停滞”的争论. 气候变化研究进展, 2016, 12(6): 571-574.]
IPCC第五次评估报告[1] (AR5)给出近15年全球年平均地表温度的变暖趋势有“停滞(hiatus)”,即从1998-2012年4套全球年平均地表温度观测资料计算得到变暖趋势是:(0.05±0.10)℃/10a.在AR5撰写过程中和2013年正式发表以来,对于近15年全球变暖是否出现停滞一直存在争议:是否出现了停滞?停滞的原因?为什么众多模式在考虑人类排放温室气体增加的历史模拟试验中都没有模拟出近些年的停滞?人类排放温室气体一直在增加,变暖却停滞,全球变暖是温室气体排放增加造成的吗?
[13] Cowtan K, Way R G.Coverage bias in the HadCRUT4 temperature series and its impact on recent temperature trends. Quarterly Journal of the Royal Meteorological Society, 2014, 140(683): 1935-1944.
Abstract Incomplete global coverage is a potential source of bias in global temperature reconstructions if the unsampled regions are not uniformly distributed over the planet's surface. The widely used Hadley Centre limatic Reseach Unit Version 4 (HadCRUT4) dataset covers on average about 84% of the globe over recent decades, with the unsampled regions being concentrated at the poles and over Africa. Three existing reconstructions with near-global coverage are examined, each suggesting that HadCRUT4 is subject to bias due to its treatment of unobserved regions. Two alternative approaches for reconstructing global temperatures are explored, one based on an optimal interpolation algorithm and the other a hybrid method incorporating additional information from the satellite temperature record. The methods are validated on the basis of their skill at reconstructing omitted sets of observations. Both methods provide results superior to excluding the unsampled regions, with the hybrid method showing particular skill around the regions where no observations are available. Temperature trends are compared for the hybrid global temperature reconstruction and the raw HadCRUT4 data. The widely quoted trend since 1997 in the hybrid global reconstruction is two and a half times greater than the corresponding trend in the coverage-biased HadCRUT4 data. Coverage bias causes a cool bias in recent temperatures relative to the late 1990s, which increases from around 1998 to the present. Trends starting in 1997 or 1998 are particularly biased with respect to the global trend. The issue is exacerbated by the strong El Ni o event of 1997 1998, which also tends to suppress trends starting during those years.
DOI:10.1002/qj.2297      [本文引用:2]
[14] Karl T R, Arguez A, Huang B, et al.Possible artifacts of data biases in the recent global surface warming hiatus. Science, 2015, 348(6242): 1469-1472.
Abstract Much study has been devoted to the possible causes of an apparent decrease in the upward trend of global surface temperatures since 1998, a phenomenon that has been dubbed the global warming "hiatus." Here, we present an updated global surface temperature analysis that reveals that global trends are higher than those reported by the Intergovernmental Panel on Climate Change, especially in recent decades, and that the central estimate for the rate of warming during the first 15 years of the 21st century is at least as great as the last half of the 20th century. These results do not support the notion of a "slowdown" in the increase of global surface temperature. Copyright 2015, American Association for the Advancement of Science.
DOI:10.1126/science.aaa5632      PMID:26044301      [本文引用:7]
[15] Huang J, Zhang X, Zhang Q, et al.Recently amplified arctic warming has contributed to a continual global warming trend. Nature Climate Change, 2017, 7(12): 875-879.
The existence and magnitude of the recently suggested global warming hiatus, or slowdown, have been strongly debated. Although various physical processeshave been examined to elucidate this phenomenon, the accuracy and completeness of observational data that comprise global average surface air temperature (SAT) datasets is a concern. In particular, these datasets lack either complete geographic coverage or in situ observations over the Arctic, owing to the sparse observational network in this area. As a consequence, the contribution of Arctic warming to global SAT changes may have been underestimated, leading to an uncertainty in the hiatus debate. Here, we constructed a new Arctic SAT dataset using the most recently updated global SATsand a drifting buoys based Arctic SAT datasetthrough employing the `data interpolating empirical orthogonal functions' method. Our estimate of global SAT rate of increase is around 0.112 C per decade, instead of 0.05 C per decade from IPCC AR5, for 1998-2012. Analysis of this dataset shows that the amplified Arctic warming over the past decade has significantly contributed to a continual global warming trend, rather than a hiatus or slowdown.
DOI:10.1038/s41558-017-0009-5      [本文引用:4]
[16] Su Jingzhi, Wen Min, Ding Yihui, et al.Hiatus of global warming: A review. Chinese Journal of Atmospheric Sciences, 2016, 40(6): 1143-1153.
[本文引用:2]
[苏京志, 温敏, 丁一汇, . 全球变暖趋缓研究进展. 大气科学, 2016, 40(6): 1143-1153.]
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。
[17] Meehl G A, Arblaster J M, Fasullo J T, et al.Model-based evidence of deep-ocean heat uptake during surface-temperature hiatus periods. Nature Climate Change, 2011, 1(7): 360-364.
There have been decades, such as 2000-2009, when the observed globally averaged surface-temperature time series shows little increase or even a slightly negative trend (a hiatus period). However, the observed energy imbalance at the top-of-atmosphere for this recent decade indicates that a net energy flux into the climate system of about 1Wm(refs , ) should be producing warming somewhere in the system. Here we analyse twenty-first-century climate-model simulations that maintain a consistent radiative imbalance at the top-of-atmosphere of about 1Wmas observed for the past decade. Eight decades with a slightly negative global mean surface-temperature trend show that the ocean above 300m takes up significantly less heat whereas the ocean below 300m takes up significantly more, compared with non-hiatus decades. The model provides a plausible depiction of processes in the climate system causing the hiatus periods, and indicates that a hiatus period is a relatively common climate phenomenon and may be linked to La Ni a-like conditions.
DOI:10.1038/nclimate1229      [本文引用:3]
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New data are presented on the changes of mean global surface air temperature and annual precipitation over extratropical continents of the Northern Hemisphere. Global warming occurred during the last century with a mean trend of 0.5°C/100 years. It is shown that for the same period the annual precipitation over the land in the 35°-70°N zone increased by 6%. The observed variations of precipitation coincide with the results of general circulation modeling of doubled COequilibrium climate change by sign but contradict by scale.
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[22] Trenberth K E, Fasullo J T, Branstator G, et al.Seasonal aspects of the recent pause in surface warming. Nature Climate Change, 2014, 4(10): 911-916.
Factors involved in the recent pause in the rise of global mean temperatures are examined seasonally. For 1999 to 2012, the hiatus in surface warming is mainly evident in the central and eastern Pacific. It is manifested as strong anomalous easterly trade winds, distinctive sea-level pressure patterns, and large rainfall anomalies in the Pacific, which resemble the Pacific Decadal Oscillation (PDO). These features are accompanied by upper tropospheric teleconnection wave patterns that extend throughout the Pacific, to polar regions, and into the Atlantic. The extratropical features are particularly strong during winter. By using an idealized heating to force a comprehensive atmospheric model, the large negative anomalous latent heating associated with the observed deficit in central tropical Pacific rainfall is shown to be mainly responsible for the global quasi-stationary waves in the upper troposphere. The wave patterns in turn created persistent regional climate anomalies, increasing the odds of cold winters in Europe. Hence, tropical Pacific forcing of the atmosphere such as that associated with a negative phase of the PDO produces many of the pronounced atmospheric circulation anomalies observed globally during the hiatus.
DOI:10.1038/nclimate2341      [本文引用:2]
[23] Jones P D, Lister D H, Osborn T J, et al.Hemispheric and large-scale land-surface air temperature variations: An extensive revision and an update to 2010. Journal of Geophysical Research Atmospheres, 2012, 117: D05127. doi: 10.1029/2011JD017139.
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[25] Kosaka Y, Xie S P.Recent global-warming hiatus tied to equatorial Pacific surface cooling. Nature, 2013, 501(7467): 403-407.
Despite the continued increase in atmospheric greenhouse gas concentrations, the annual-mean global temperature has not risen in the twenty-first century(1,2), challenging the prevailing view that anthropogenic forcing causes climate warming. Various mechanisms have been proposed for this hiatus in global warming(3-6), but their relative importance has not been quantified, hampering observational estimates of climate sensitivity. Here we show that accounting for recent cooling in the eastern equatorial Pacific reconciles climate simulations and observations. We present a novel method of uncovering mechanisms for global temperature change by prescribing, in addition to radiative forcing, the observed history of sea surface temperature over the central to eastern tropical Pacific in a climate model. Although the surface temperature prescription is limited to only 8.2% of the global surface, our model reproduces the annual-mean global temperature remarkably well with correlation coefficient r = 0.97 for 1970-2012 (which includes the current hiatus and a period of accelerated global warming). Moreover, our simulation captures major seasonal and regional characteristics of the hiatus, including the intensified Walker circulation, the winter cooling in northwestern North America and the prolonged drought in the southern USA. Our results show that the current hiatus is part of natural climate variability, tied specifically to a La-Nina-like decadal cooling. Although similar decadal hiatus events may occur in the future, the multi-decadal warming trend is very likely to continue with greenhouse gas increase.
DOI:10.1038/nature12534      PMID:23995690      [本文引用:4]
[26] Duan Anmin, Xiao Zhixiang, Wu Guoxiong.Characteristics of climate change over the Tibetan Plateau under the global warming during 1979-2014. Climate Change Research, 2016, 12(5): 374-381.
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[段安民, 肖志祥, 吴国雄. 1979-2014年全球变暖背景下青藏高原气候变化特征. 气候变化研究进展, 2016, 12(5): 374-381.]
<p>近几十年来全球变暖受到越来越广泛的关注,然而全球变暖从1998年开始趋缓,但青藏高原却呈现加速增暖的趋势。本文基于前人研究,系统回顾了青藏高原气温、积雪、降水和大气热源等四方面在全球变暖背景下的变化,指出高原的加速增温导致了积雪迅速融化,降水明显增多的同时,高原热源却呈现减弱趋势。</p>
[27] Schneider N, Cornuelle B D.The forcing of the Pacific Decadal Oscillation. Journal of Climate, 2005, 18(21): 4355-4373.
The Pacific decadal oscillation (PDO), defined as the leading empirical orthogonal function of North Pacific sea surface temperature anomalies, is a widely used index for decadal variability. It is shown that the PDO can be recovered from a reconstruction of North Pacific sea surface temperature anomalies based on a first-order autoregressive model and forcing by variability of the Aleutian low, El Ni01±o09“Southern Oscillation (ENSO), and oceanic zonal advection anomalies in the Kuroshio09“Oyashio Extension. The latter results from oceanic Rossby waves that are forced by North Pacific Ekman pumping. The SST response patterns to these processes are not orthogonal, and they determine the spatial characteristics of the PDO. The importance of the different forcing processes is frequency dependent. At interannual time scales, forcing from ENSO and the Aleutian low determines the response in equal parts. At decadal time scales, zonal advection in the Kuroshio09“Oyashio Extension, ENSO, and anomalies of the Aleutian low each account for similar amounts of the PDO variance. These results support the hypothesis that the PDO is not a dynamical mode, but arises from the superposition of sea surface temperature fluctuations with different dynamical origins.
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[28] Liu Chao.Study on influence of the PDO on sea level rise in the Pacific [D]. Qingdao: University of Chinese Academy of Sciences, 2016.
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[29] Hoyt D V, Schatten K H.The Role of the Sun in Climate Change. New York: Oxford University Press, 1997.
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[30] Lean J L.Cycles and trends in solar irradiance and climate. Wiley Interdisciplinary Reviews: Climate Change, 2010, 1(1): 111-122.
How - indeed whether - the Sun's variable energy outputs influence Earth's climate has engaged scientific curiosity for more than a century. Early evidence accrued from correlations of assorted solar and climate indices, and from recognition that cycles near 11, 88 and 205 years are common in both the Sun and climate.[ 1 ][ 2 ] But until recently, an influence of solar variability on climate, whether through cycles or trends, was usually dismissed because climate simulations with (primarily) simple energy balance models indicated that responses to the decadal solar cycle would be so small as to be undetectable in observations.[ 3 ] However, in the past decade modeling studies have found both resonant responses and positive feedbacks in the ocean-atmosphere system that may amplify the response to solar irradiance variations.[ 4 ][ 5 ] Today, solar cycles and trends are recognized as important components of natural climate variability on decadal to centennial time scales. Understanding solar-terrestrial linkages is requisite for the comprehensive understanding of Earth's evolving environment. The attribution of present-day climate change, interpretation of changes prior to the industrial epoch, and forecast of future decadal climate change necessitate quantitative understanding of how, when, where, and why natural variability, including by the Sun, may exceed, obscure or mitigate anthropogenic changes. Copyright 2010 John Wiley &amp; Sons, Ltd. For further resources related to this article, please visit the WIREs website .
DOI:10.1002/wcc.18      [本文引用:1]
[31] Coddington O, Lean J L, Pilewskie P, et al.A solar irradiance climate data record. Bulletin of the American Meteorological Society, 2016, 97(7): 1265-1282.
We present a new climate data record for total solar irradiance and solar spectral irradiance between 1610 and the present day with associated wavelength and time-dependent uncertainties and quarterly updates. The data record, which is part of the National Oceanic and Atmospheric Administration090005s (NOAA) Climate Data Record (CDR) program, provides a robust, sustainable, and scientifically defensible record of solar irradiance that is of sufficient length, consistency, and continuity for use in studies of climate variability and climate change on multiple time scales and for user groups spanning climate modeling, remote sensing, and natural resource and renewable energy industries. The data record, jointly developed by the University of Colorado090005s Laboratory for Atmospheric and Space Physics (LASP) and the Naval Research Laboratory (NRL), is constructed from solar irradiance models that determine the changes with respect to quiet sun conditions when facular brightening and sunspot darkening features are present on the solar disk where the magnitude of the changes in irradiance are determined from the linear regression of a proxy magnesium (Mg) II index and sunspot area indices against the approximately decade-long solar irradiance measurements of the Solar Radiation and Climate Experiment (SORCE). To promote long-term data usage and sharing for a broad range of users, the source code, the dataset itself, and supporting documentation are archived at NOAA's National Centers for Environmental Information (NCEI). In the future, the dataset will also be available through the LASP Interactive Solar Irradiance Data Center (LISIRD) for user-specified time periods and spectral ranges of interest.
DOI:10.1175/BAMS-D-14-00265.1      [本文引用:1]
[32] Friis-Christensen E, Lassen K.Length of the solar cycle: An indicator of solar activity closely associated with climate. Science, 1991, 254(5032): 698-700.
It has recently been suggested that the solar irradiance has varied in phase with the 80- to 90-year period represented by the envelope of the 11-year sunspot cycle and that this variation is causing a significant part of the changes in the global temperature. This interpretation has been criticized for statistical reasons and because there are no observations that indicate significant changes in the solar irradiance. A set of data that supports the suggestion of a direct influence of solar activity on global climate is the variation of the solar cycle length. This record closely matches the long-term variations of the Northern Hemisphere land air temperature during the past 130 years.
DOI:10.1126/science.254.5032.698      PMID:17774798      [本文引用:1]
[33] Hassani H, Huang X, Gupta R, et al.Does sunspot numbers cause global temperatures? A reconsideration using non-parametric causality tests. Physica A: Statistical Mechanics and its Applications, 2016, 460: 54-65.
DOI:10.1016/j.physa.2016.04.013      [本文引用:1]
[34] Rathod M, Gupta M, Shrivastava A K.Long-term variation of solar flare indices in relation to sunspot numbers from Solar Cycle 20 to 24. Journal of Pure Applied and Industrial Physics, 2017, 7(9): 339-347.
DOI:10.29055/jpaip/288      [本文引用:1]
[35] Cohen J, Barlow M, Saito K.Decadal fluctuations in planetary wave forcing modulate global warming in late boreal winter. Journal of Climate, 2009, 22(16): 4418-4426.
The warming trend in global surface temperatures over the last 40 yr is clear and consistent with anthropogenic increases in greenhouse gases. Over the last 2 decades, this trend appears to have accelerated. In contrast to this general behavior, however, here it is shown that trends during the boreal cold months in the recent period have developed a marked asymmetry between early winter and lat...
DOI:10.1175/2009JCLI2931.1      [本文引用:1]
[36] Seager R, Kushnir Y, Nakamura J, et al.Northern Hemisphere winter snow anomalies: ENSO, NAO and the winter of 2009/10. Geophysical Research Letters, 2010, 37: L14703. doi: 10.1029/2010GL043830.
Winter 2009/10 had anomalously large snowfall in the central parts of the United States and in northwestern Europe. Connections between seasonal snow anomalies and the large scale atmospheric circulation are explored. An El Ni o state is associated with positive snowfall anomalies in the southern and central United States and along the eastern seaboard and negative anomalies to the north. A negative NAO causes positive snow anomalies across eastern North America and in northern Europe. It is argued that increased snowfall in the southern U.S. is contributed to by a southward displaced storm track but further north, in the eastern U.S. and northern Europe, positive snow anomalies arise from the cold temperature anomalies of a negative NAO. These relations are used with observed values of NINO3 and the NAO to conclude that the negative NAO and El Ni o event were responsible for the northern hemisphere snow anomalies of winter 2009/10.
DOI:10.1029/2010GL043830      [本文引用:1]
[37] Cattiaux J, Vautard R, Cassou C, et al.Winter 2010 in Europe: A cold extreme in a warming climate. Geophysical Research Letters, 2010, 37: L20704. doi: 10.1029/2010GL044613.
The winter of 2009/2010 was characterized by record persistence of the negative phase of the North-Atlantic Oscillation (NAO) which caused several severe cold spells over Northern and Western Europe. This somehow unusual winter with respect to the most recent ones arose concurrently with public debate on climate change, during and after the Copenhagen climate negotiations. We show however that the cold European temperature anomaly of winter 2010 was (i) not extreme relative to winters of the past six decades, and (ii) warmer than expected from its record-breaking seasonal circulation indices such as NAO or blocking frequency. Daily flow-analogues of winter 2010, taken in past winters, were associated with much colder temperatures. The winter 2010 thus provides a consistent picture of a regional cold event mitigated by long-term climate warming. Citation: Cattiaux, J., R. Vautard, C. Cassou, P. Yiou, V. Masson-Delmotte, and F. Codron (2010), Winter 2010 in Europe: A cold extreme in a warming climate, Geophys. Res. Lett., 37, L20704, doi:10.1029/2010GL044613.
DOI:10.1029/2010GL044613      [本文引用:1]
[38] Ding Yihui, Ma Xiaoqing.Analysis of isentropic potential vorticity for a strong cold wave in 2004/2005 winter. Acta Meteorologica Sinica, 2007, 65(5): 695-707.
[本文引用:1]
[丁一汇, 马晓青. 2004/2005年冬季强寒潮事件的等熵位涡分析. 气象学报, 2007, 65(5): 695-707.]
利用2004年12月1日—2005年2月28日的NCAR/NCEP逐日再分析资料,对2004年12月22日—2005年1月1日的强寒潮事件进行等熵位涡分析。结果表明:这次强寒潮事件的强冷空气来自欧亚北部和北极地区的高纬平流层下部与对流层上部。在寒潮爆发前期,高位涡强冷空气传播到贝加尔湖南侧,并被来自低纬度的低位涡空气所切断,在欧亚地区形成北部低位涡(阻塞高压)南部高位涡(低涡)的偶极型环流。随着低位涡的减弱消亡,高位涡强冷空气沿高原北侧向东南方向移动,当高位涡中心移到中国东部地区,高位涡空气柱在垂直方向上强烈向下伸展,使得气柱的气旋性涡度加强,东亚大槽迅速加深,引起寒潮的爆发。进一步分析表明,高位涡中心向南、向下传播过程中,等熵面上高位涡中心附近气流在其西侧和北侧地区沿等熵面下沉,引起上述地区低层西伯利亚高压迅速发展,导致强寒潮爆发。
DOI:10.11676/qxxb2007.065     
[39] Hong C C, Li T.The extreme cold anomaly over Southeast Asia in February 2008: Roles of ISO and ENSO. Journal of Climate, 2009, 22(13): 3786-3801.
A record-breaking, long-persisting extreme cold anomaly (ECA) over Southeast Asia, accompanied by an intraseasonal convection over the Maritime Continent, is identified during the La Ni09a mature phase in February 2008. The cause of the ECA, in particular the role of the intraseasonal oscillation (ISO) and El Ni09o-Southern Oscillation (ENSO) on the ECA, is investigated by diagnosing observations...
DOI:10.1175/2009JCLI2864.1      [本文引用:1]
[40] Wen M, Yang S, Kumar A, et al.An analysis of the large-scale climate anomalies associated with the snowstorms affecting China in January 2008. Monthly Weather Review, 2009, 137(3): 1111-1131.
DOI:10.1175/2008MWR2638.1      [本文引用:1]
[41] Zhang Ziyin, Gong Daoyi, Guo Dong, et al.Anomalous winter temperature and precipitation events in southern China. Acta Geographica Sinica, 2008, 63(9): 899-912.
[本文引用:1]
[张自银, 龚道溢, 郭栋, . 我国南方冬季异常低温和异常降水事件分析. 地理学报, 2008, 63(9): 899-912.]
[42] Lin Xiaopei, Xu Lixiao, Li Jianping, et al.Research on the global warming hiatus. Advances in Earth Science, 2016, 31(10): 995-1000.
[本文引用:1]
[林霄沛, 许丽晓, 李建平, . 全球变暖“停滞”现象辨识与机理研究. 地球科学进展, 2016, 31(10): 995-1000.]
观测表明全球温室气体浓度持续快速增加,但21世纪以来全球表面平均温度升高有减缓趋势,呈现变暖&#x0201c;停滞&#x0201d;现象,这对已有的全球变暖认识带来挑战。围绕&#x0201c;变暖&#x02018;停滞&#x02019;机理及其可预测性&#x0201d;这一国际前沿科学问题,国家重点研发计划&#x0201c;全球变暖&#x02018;停滞&#x02019;现象辨识与机理研究&#x0201d;主要研究内容有:①辨识变暖&#x0201c;停滞&#x0201d;的时空特征,阐明外部强迫和内部自然变率的相对贡献;②阐明全球变暖停滞背景下,大气在气候系统能量热量再分配过程中的作用及机理;③阐明全球变暖&#x0201c;停滞&#x0201d;背景下,海洋动力热力过程对能量热量再分配的调制机理;④探讨全球变暖&#x0201c;停滞&#x0201d;现象的可预测性,对其未来变化及重要区域气候影响进行预测预估。以期通过变暖&#x0201c;停滞&#x0201d;研究回答人们所关心的目前变暖停滞现象未来发展及其对我国及周边的&#x0201c;一带一路&#x0201d;核心区和南北极重要区域的影响,为我国未来气候政策的制定提供参考依据,为国家参与全球气候治理及国际气候谈判提供科学支撑。
[43] Schmidt G A, Shindell D T, Tsigaridis K.Reconciling warming trends. Nature Geoscience, 2014, 7(3): 158-160.
DOI:10.1038/ngeo2105      [本文引用:1]
[44] Dai A, Fyfe J C, Xie S P, et al.Decadal modulation of global surface temperature by internal climate variability. Nature Climate Change, 2015, 5(6): 555-559.
Despite a steady increase in atmospheric greenhouse gases (GHGs), global-mean surface temperature (T) has shown nodiscernible warming since about 2000, in sharp contrast to model simulations, which on average project strongwarming1–3.The recent slowdown in observed surface warming has been attributed to decadal cooling in the tropical Pacific1,4,5, intensifying trade winds5, changes in El Ni09o activity6,7, increasing volcanic activity8–10 and decreasing solar irradiance7.Earlier periods of arrested warming have been observed but received much less attention than the recent period, and their causes are poorly understood. Here we analyse observed and model-simulated global T fields to quantify the contributions of internal climate variability (ICV) to decadal changes in global-mean T since 1920. We show that the Interdecadal Pacific Oscillation (IPO) has been associated with large T anomalies over both ocean and land. Combined with another leading mode of ICV, the IPO explains most of the dierence between observed and model-simulated rates of decadal change in global-mean T since 1920, and particularlyover the so-called ‘hiatus’ period since about2000. We conclude that ICV, mainly through the IPO, was largely responsible for the recent slowdown, as well as for earlier slowdowns and accelerations in global-mean T since 1920, with preferred spatial patterns dierent from those associated with GHG-inducedwarming or aerosol-induced cooling. Recent history suggests that the IPO could reverse course and lead to accelerated global warming in the coming decades.
DOI:10.1038/nclimate2605      [本文引用:1]
[45] Li J, Sun C, Jin F F.NAO implicated as a predictor of Northern Hemisphere mean temperature multidecadal variability. Geophysical Research Letters, 2013, 40(20): 5497-5502.
The twentieth century Northern Hemisphere mean surface temperature (NHT) is characterized by a multidecadal warming-cooling-warming pattern followed by a flat trend since about 2000 (recent warming hiatus). Here we demonstrate that the North Atlantic Oscillation (NAO) is implicated as a useful predictor of NHT multidecadal variability. Observational analysis shows that the NAO leads both the detrended NHT and oceanic Atlantic Multidecadal Oscillation (AMO) by 15-20 years. Theoretical analysis illuminates that the NAO precedes NHT multidecadal variability through its delayed effect on the AMO due to the large thermal inertia associated with slow oceanic processes. An NAO-based linear model is therefore established to predict the NHT, which gives an excellent hindcast for NHT in 1971-2011 with the recent flat trend well predicted. NHT in 2012-2027 is predicted to fall slightly over the next decades, due to the recent NAO decadal weakening that temporarily offsets the anthropogenically induced warming.
DOI:10.1002/2013GL057877      [本文引用:1]
[46] Douville H, Voldoire A, Geoffroy O.The recent global warming hiatus: What is the role of Pacific variability? Geophysical Research Letters, 2015, 42(3): 880-888.
Abstract The observed global mean surface air temperature (GMST) has not risen over the last 1565years, spurring outbreaks of skepticism regarding the nature of global warming and challenging the upper range transient response of the current-generation global climate models. Recent numerical studies have, however, tempered the relevance of the observed pause in global warming by highlighting the key role of tropical Pacific internal variability. Here we first show that many climate models overestimate the influence of the El Ni09o–Southern Oscillation on GMST, thereby shedding doubt on their ability to capture the tropical Pacific contribution to the hiatus. Moreover, we highlight that model results can be quite sensitive to the experimental design. We argue that overriding the surface wind stress is more suitable than nudging the sea surface temperature for controlling the tropical Pacific ocean heat uptake and, thereby, the multidecadal variability of GMST. Using the former technique, our model captures several aspects of the recent climate evolution, including the weaker slowdown of global warming over land and the transition toward a negative phase of the Pacific Decadal Oscillation. Yet the observed global warming is still overestimated not only over the recent 1998–2012 hiatus period but also over former decades, thereby suggesting that the model might be too sensitive to the prescribed radiative forcings.
DOI:10.1002/2014GL062775      [本文引用:1]
[47] Yao S L, Huang G, Wu R G, et al.The global warming hiatus: A natural product of interactions of a secular warming trend and a multi-decadal oscillation. Theoretical and Applied Climatology, 2016, 123(1/2): 349-360.
DOI:10.1007/s00704-014-1358-x      [本文引用:1]
[48] Deser C, Guo R, Lehner F.The relative contributions of tropical Pacific sea surface temperatures and atmospheric internal variability to the recent global warming hiatus. Geophysical Research Letters, 2017, 44(15): 7945-7954.
DOI:10.1002/2017GL074273      [本文引用:0]