East Anglia Climatic Research Unit Research Articles

气候变化下中国不同植被区总初级生产力对干旱的响应

PDF HTML阅读 XML下载 导出引用 引用提醒 气候变化下中国不同植被区总初级生产力对干旱的响应 DOI: 10.5846/stxb202010232707 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家重点研发计划资助（2019YFAO606900）；国家自然科学基金面上基金项目（42077436） Response of gross primary production to drought under climate change in different vegetation regions of China Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:干旱变化具有明显的空间分异，不同植被类型对干旱的响应亦有差别。开展气候变化下不同植被覆盖类型对干旱响应的差异分析，厘清温升干旱化进程对植被的影响，对了解植被发展动态及预测未来格局有着非常重要的意义。基于1982-2017年的总初级生产力（GPP）数据和同时期东安格利亚大学气候研究中心（CRU）时间序列（TS）气候数据，分析了中国8个植被区GPP和干旱的变化趋势，通过对比标准化降水指数（SPI）和标准化降水蒸散指数（SPEI）的趋势差异识别了典型的温升干旱化区域，在此基础上研究气温上升如何影响GPP对干旱的响应，进一步讨论了不同植被类型对干旱的敏感性差异。结果表明：（1）36年来8个植被区除青藏高原高寒植被区呈湿润化，其他植被区均呈现变干趋势；（2）气温上升大面积加剧了温带荒漠区和温带草原区的变干趋势；（3）亚热带常绿阔叶林区和热带季风雨林、雨林区的GPP受温度和干旱影响相当，青藏高原高寒植被区和针叶、落叶林混交林区的GPP受温度主导，其他植被区GPP均受干旱主导。 Abstract:Variations of drought have obviously spatial differentiation, and different vegetation types have different responses to drought. However, few studies have been conducted to distinguish the contribution of temperature increase to the variations of drought and to investigate the differences in the responses of different vegetation types to warming aridification on a large scale. Analyzing differences in the response of different vegetation cover types to drought under climate change and clarifying the impact of warming aridification on vegetation in China are of great importance for understanding the development dynamics of vegetation and predicting future patterns. In this study, based on climatic data from the University of East Anglia Climatic Research Unit (CRU) Time-series (TS) version 4.04 dataset, the standardized precipitation index (SPI) and standardized precipitation evapotranspiration index (SPEI) were calculated in 1982-2017. Using Theil-Sen median trend analysis and the Mann-Kendall test, we analyzed trends in gross primary production (GPP) and drought in the eight vegetation regions of China. By comparing the trend differences between SPI and SPEI, typical warming aridification areas were identified under three scenarios ([SPI not significantly drier+SPEI significantly drier],[SPI wetter+ SPEI not significantly drier], and[SPI wetter+SPEI significantly drier]). Finally, after detrending GPP and temperature, the correlation analysis and multiple regression were used to investigate how temperature increase affected the response of GPP to drought and further discuss the differences in sensitivity of different vegetation regions to drought. The results showed that all eight vegetation regions showed a drying trend over past 36 years, except for Qinghai-Tibet plateau high cold vegetation region, which was getting wet. The GPP of each vegetation region mainly increased, among which the Qinghai-Tibet plateau high cold vegetation region showed the most significant increase in GPP, which might be related to the warming and wetting trend in this region. The temperature increase had the strongest exacerbating effect on drying in temperate desert region and temperate steppe region, and the weakest exacerbating effect on drying in temperate needleleaf and broadleaf forest region and cold temperate needleleaf forest region, while it significantly increased the sensitivity of GPP to drought in the latter. There was variability in the response of GPP to temperature and drought conditions in different vegetation regions:the GPP of the subtropical evergreen broad-leaved forest region and the tropical monsoon forest and rain forest region was comparably affected by both temperature and drought, the GPP of the Qinghai-Tibet plateau high cold vegetation region and temperate needleleaf and broadleaf forest region was dominantly affected by temperature, and the GPP in all other vegetation regions was mainly affected by drought. 参考文献 相似文献 引证文献

Historical and future global burned area with changing climate and human demography

Summary Wildfires influence terrestrial carbon cycling and represent a safety risk, and yet a process-based understanding of their frequency and spatial distributions remains elusive. We combine satellite-based observations with an enhanced dynamic global vegetation model to make regionally resolved global assessments of burned area (BA) responses to changing climate, derived from 34 Earth system models and human demographics for 1860–2100. Limited by climate and socioeconomics, recent BA has decreased, especially in central South America and mesic African savannas. However, future simulations predict increasing BA due to changing climate, rapid population density growth, and urbanization. BA increases are especially notable at high latitudes, due to accelerated warming, and over the tropics and subtropics, due to drying and human ignitions. Conversely, rapid urbanization also limits BA via enhanced fire suppression in the immediate vicinity of settlements, offsetting the potential for dramatic future increases, depending on warming extent. Our analysis provides further insight into regional and global BA trends, highlighting the importance of including human demographic change in models for wildfire under changing climate.

The precipitation variability of the wet and dry season at the interannual and interdecadal scales over eastern China (1901–2016): the impacts of the Pacific Ocean

Abstract. The spatiotemporal variability of rainfall in the dry (October–March) and wet (April–September) seasons over eastern China is examined from 1901–2016 based on the gridded rainfall dataset from the University of East Anglia Climatic Research Unit. Principal component analysis is employed to identify the dominant variability modes, wavelet coherence is utilized to investigate the spectral features of the leading modes of precipitation and their coherences with the large-scale modes of climate variability, and the Bayesian dynamical linear model is adopted to quantify the time-varying correlations between climate variability modes and rainfall in the dry and wet seasons. Results show that first and second principal components (PCs) account for 34.2 % (16.1 %) and 13.4 % (13.9 %) of the variance in the dry (wet) season, and their variations are roughly coincident with phase shifts of the El Niño–Southern Oscillation (ENSO) in both seasons. The anomalous moisture fluxes responsible for the occurrence of precipitation events in eastern China exhibit an asymmetry between high and light rainfall years in the dry (wet) season. The ENSO has a 4- to 8-year signal of the statistically positive (negative) association with rainfall during the dry (wet) season over eastern China. The statistically significant positive (negative) associations between the Pacific Decadal Oscillation (PDO) and precipitation are found with a 9- to 15-year (4- to 7-year) signal. The impacts of the PDO on rainfall in eastern China exhibit multiple timescales as compared to the ENSO episodes, while the PDO triggers a stronger effect on precipitation in the wet season than the dry half year. The interannual and interdecadal variations in rainfall over eastern China are substantially modulated by drivers originated from the Pacific Ocean. During the wet season, the ENSO exerted a gradually weakening effect on eastern China rainfall from 1901 to 2016, while the effects of the PDO decreased before the 1980s, and then shifted into increases after the 2000s. The finding provides a metric for assessing the capability of climate models and guidance of seasonal prediction.

Impacts of Heat and Drought on Gross Primary Productivity in China

Heat and drought stress, which often occur together, are the main environmental factors limiting the survival and growth of vegetation. Studies on the response of gross primary production (GPP) to extreme climate events such as heat and drought are highly significant for the identification of ecologically vulnerable regions, ecological risk assessments, and ecological environmental protection. We got 1982–2017 climatic data from the University of East Anglia Climatic Research Unit, Norwich, England, and GPP data from National Earth System Science Data Sharing Service Platform, Beijing, China. Using Theil–Sen median trend analysis and the Mann–Kendall test, we analyzed trends in temperature and the standardized precipitation/standardized precipitation evapotranspiration indices in the eight vegetation regions of China. Additionally, the response of GPP to the single and combined impacts of heat and drought were analyzed using multidimensional copula functions, and GPP reduction probabilities were estimated under different drought levels and heat intensities. The results showed that the probability of a drastic GPP reduction increases with increasing drought levels and heat intensities. The combined impacts of heat and drought on vegetation productivity is greater than the impacts of either drought or heat alone and presents a nonlinear superposition of the two extremes. The impact of heat on GPP is not evident when the drought level is high. The temperate grassland and warm temperate deciduous broad-leaved forest regions are the most sensitive regions to drought and heat in China. This study provides a scientific basis for the comprehensive evaluation of the risk of GPP reduction under the single and combined impacts of heat stress and drought stress.

Variability of soil freeze depth in association with climate change from 1901 to 2016 in the upper Brahmaputra River Basin, Tibetan Plateau

Soil freeze depth (SFD) is necessary to evaluate the variations in water resource balances, surface energy exchanges, and biogeochemical cycles in the frozen ground regions, while the variability of regional SFD under climate changes remains unknown, mainly due to the insufficiency of effective observations. Significant changes of frozen ground related to water resources and the eco-environment have occurred in the Upper Brahmaputra River Basin (UBRB) (also known as the Yarlung Zangbo River) on the southern Tibetan Plateau, which is a key area where SFD monitoring is scarce. In this study, we adopted the Stefan equation to simulate the regional maximum SFD over the UBRB from 1901 to 2016 with monthly near-surface air temperatures from the University of East Anglia Climatic Research Unit (UEA-CRU) and the University of Delaware (UDEL). Observations from 11 national meteorological stations over the UBRB and 6 nearby were used to calibrate relevant parameters and evaluate the simulations. Studies showed that maximum SFD is positively correlated with air freezing index (AFI), ground surface freezing index (GFI), and snow depth (SD) and is negatively correlated with air thawing index (ATI), ground surface thawing index (GTI), mean annual air temperature (MAAT), and mean annual ground surface temperature (MAGST). Approximately 97.94% and 96.21% of the UBRB were covered with the frozen ground as simulated with the UEA-CRU and the UDEL, respectively. The maximum SFD calculated with the UEA-CRU and the UDEL decreased respectively by about 0.31 m and 0.15 m over the past 116 years. Simulations with both datasets demonstrated that no significant changes of SFD occurred in the past four 30-year periods (i.e., 1901–1930, 1931–1960, 1961–1990, and 1991–2016), while the maximum SFD calculated with the UEA-CRU was smaller than that with the UDEL. All of these features demonstrated a warming trend of frozen ground from 1901 to 2016 in the UBRB.

A High-Resolution 1983–2016 Tmax Climate Data Record Based on Infrared Temperatures and Stations by the Climate Hazard Center

AbstractUnderstanding the dynamics and physics of climate extremes will be a critical challenge for twenty-first-century climate science. Increasing temperatures and saturation vapor pressures may exacerbate heat waves, droughts, and precipitation extremes. Yet our ability to monitor temperature variations is limited and declining. Between 1983 and 2016, the number of observations in the University of East Anglia Climatic Research Unit (CRU) Tmax product declined precipitously (5900 → 1000); 1000 poorly distributed measurements are insufficient to resolve regional Tmax variations. Here, we show that combining long (1983 to the near present), high-resolution (0.05°), cloud-screened archives of geostationary satellite thermal infrared (TIR) observations with a dense set of ~15 000 station observations explains 23%, 40%, 30%, 41%, and 1% more variance than the CRU globally and for South America, Africa, India, and areas north of 50°N, respectively; even greater levels of improvement are shown for the 2011–16 period (28%, 45%, 39%, 52%, and 28%, respectively). Described here for the first time, the TIR Tmax algorithm uses subdaily TIR distributions to screen out cloud-contaminated observations, providing accurate (correlation ≈0.8) gridded emission Tmax estimates. Blending these gridded fields with ~15 000 station observations provides a seamless, high-resolution source of accurate Tmax estimates that performs well in areas lacking dense in situ observations and even better where in situ observations are available. Cross-validation results indicate that the satellite-only, station-only, and combined products all perform accurately (R ≈ 0.8–0.9, mean absolute errors ≈ 0.8–1.0). Hence, the Climate Hazards Center Infrared Temperature with Stations (CHIRTSmax) dataset should provide a valuable resource for climate change studies, climate extreme analyses, and early warning applications.

Heterogeneity of Scaling of the Observed Global Temperature Data

AbstractWe investigated the scaling properties of two datasets of the observed near-surface global temperature data anomalies: the Met Office and the University of East Anglia Climatic Research Unit HadCRUT4 dataset and the NASA GISS Land–Ocean Temperature Index (LOTI) dataset. We used detrended fluctuation analysis of second-order (DFA2) and wavelet-based spectral (WTS) analysis to investigate and quantify the global pattern of scaling in two datasets and to better understand cyclic behavior as a possible underlying cause of the observed forms of scaling. We found that, excluding polar and parts of subpolar regions because of their substantial data inhomogeneity, the global temperature pattern is long-range autocorrelated. Our results show a remarkable heterogeneity in the long-range dynamics of the global temperature anomalies in both datasets. This finding is in agreement with previous studies. We additionally studied the DFA2 and the WTS behavior of the local station temperature anomalies and satellite-based temperature estimates and found that the observed diversity of global scaling can be attributed both to the intrinsic variability of data and to the methodology-induced variations that arise from deriving the global temperature gridded data from the original local sources. Finally, we found differences in global temperature scaling patterns of the two datasets and showed instances where spurious scaling is introduced in the global datasets through a spatial infilling procedure or the optimization of integrated satellite records.

Space–time variability of Indonesian rainfall at inter-annual and multi-decadal time scales

We investigated the space–time variability of wet (Nov–Apr) and dry (May–Oct) season rainfall over Indonesia, using monthly gridded rainfall data from the University of East Anglia Climatic Research Unit covering the period 1901–2012. Three complimentary techniques were employed—(1) principal component analysis to identify the dominant modes of variability, (2) wavelet spectral analysis to identify the spectral characteristics of the leading modes and their coherence with large scale climate variables and (3) Bayesian Dynamical Linear Model (BDLM) to quantify the temporal variability of the association between rainfall modes and climate variables. In the dry season when the Inter Tropical Convergence Zone (ITCZ) is to the north of the equator the leading two principal components (PCs) explain close to 50 % of the rainfall. In the wet season the ITCZ moves to the south and the leading PCs explain close to 30 % of the variance. El Nino Southern Oscillation (ENSO) is the driver of the leading modes of rainfall variability during both seasons. We find asymmetry in the teleconnections of ENSO to high and low rainfall years in the dry season. Furthermore, ENSO and the leading PCs of rainfall have spectral coherence in the inter-annual band (2–8 years) over the entire period of record and in the multi-decadal (8–16 years) band in post-1980 years. In addition, during the 1950–1980 period the second mode of variability in both seasons has a strong relationship with Pacific Decadal Oscillation. The association between ENSO and the leading mode of Indonesian rainfall has strengthened in recent decades, more so during dry season. These inter-annual and multi-decadal variability of Indonesian rainfall modulated by Pacific climate drivers has implications for rainfall and hydrologic predictability important for water resources management.

The impact of using different modern climate data sets in pollen-based paleoclimate reconstructions of North America

The use of different modern climate data sets is shown to impact a continental-scale pollen-based reconstruction of mean July temperature (TJUL) over the last 2000 years for North America. Data from climate stations, physically modeled from climate stations and reanalysis products are used to calibrate the reconstructions. Results show that the use of reanalysis products produces warmer and/or smoother reconstructions as compared to the use of station based data sets. The reconstructions during the period of 1050–1550 CE are shown to be more variable because of a high latitude cold-bias in the modern TJUL data. The ultra-high resolution WorldClim gridded data may only useful if the modern pollen sites have at least the same spatial precision as the gridded dataset. Hence we justify the use of the lapse-rate corrected University of East Anglia Climate Research Unit (CRU) based Whitmore modern climate data set for North American pollen-based climate reconstructions.

Estimation of contemporary observed variations of air temperature and wind speed in the troposphere of the Northern Hemisphere

Carried out is the statistical analysis of contemporary observed variations of air temperature and wind speed in the troposphere of the Northern Hemisphere based on the data on global surface air temperature for 1850–2013 obtained from the University of East Anglia Climate Research Unit (HadCRUT4) and NCEP/NCAR reanalysis (1948–2013). Revealed are the long-term trends of air temperature and wind speed at different constant-pressure levels. Established is the anticipatory role of the zonal atmospheric circulation in the long-term variability of air temperature in the lower troposphere averaged for the zone of 30°–70° N. According to the results of correlation analysis, in some areas of the Northern Hemisphere the contribution of the wind speed to air temperature variability makes up not less than 60%.

Computation of the Standardized Precipitation Index (SPI) and Its Use to Assess Drought Occurrences in Cameroon over Recent Decades

AbstractThe standardized precipitation index (SPI) is computed and analyzed using 55 years of precipitation data recorded in 24 observation stations in Cameroon along with University of East Anglia Climate Research Unit (CRU) spatialized data. Four statistical distribution functions (gamma, exponential, Weibull, and lognormal) are first fitted to data accumulated for various time scales, and the appropriate functions are selected on the basis of the Anderson–Darling goodness-of-fit statistic. For short time scales (up to 6 months) and for stations above 10°N, the gamma distribution is the most frequent choice; below this belt, the Weibull distribution predominates. For longer than 6-month time scales, there are no consistent patterns of fitted distributions. After calculating the SPI in the usual way, operational drought thresholds that are based on an objective method are determined at each station. These thresholds are useful in drought-response decision making. From SPI time series, episodes of severe and extreme droughts are identified at many stations during the study period. Moderate/severe drought occurrences are intra-annual in short time scales and interannual for long time scales (greater than 9 months), usually spanning many years. The SPI calculated from CRU gridded precipitation shows similar results, with some discrepancies at longer scales. Thus, the spatialized dataset can be used to extend such studies to a larger region—especially data-scarce areas.

Framing of climate change in newspaper coverage of the East Anglia e-mail scandal

In late 2009, a series of e-mails related to climate research were made public following the hacking into a server and the e-mail accounts of researchers at the University of East Anglia Climate Research Unit. According to some skeptics of climate change research, the content of those e-mails suggested data were being manipulated, while climate scientists said their words were taken out of context. The news coverage of this scandal provides an opportunity to consider media framing. This study has two aims: to extend previous research using a cluster analysis technique to discern frames in media texts; and to provide insight into newspaper coverage of the scandal, which is often referred to as "Climategate." This study examines the frames present in two British and two American newspapers' coverage of the issue.

Spatial variability of annual precipitation using globally gridded data sets from 1951 to 2000

AbstractThis study assesses the variability of the amounts of annual precipitation in global land areas (excluding Greenland and Antarctica) from 1951 to 2000. The analysis is based on 0.5° longitude/latitude gridded data. Three different data sets were analysed (University of East Anglia Climate Research Unit's (UEA CRU) TS 2.1 data set, the Global Precipitation Climatology Centre's (GPCC) Full Data Reanalysis version 5 data set, Variability Analysis of Surface Climate Observations (VASClimO) version 1.1 data set), and all led to very similar results. The results included here correspond to the VasClimO project data. Precipitation variability is examined through the anomaly of the coefficient of variation, which is shown to be a robust concept. It is defined as the departure of the actual coefficient of variation from the value that could be expected ‘on average’, conditioned on the total annual amount of precipitation. A brief discussion of the so‐called Jackknife error is included. The analysis revealed diverse areas of larger‐than‐normal, smaller‐than‐normal and close‐to‐normal variability. Negative anomalies occur more often but have, on an average, lower values than do positive anomalies. Large areas of slightly negative anomalies were found inland for all continents except Australia. A zonal pattern in the distribution of the anomalies was clearly seen at subtropical latitudes, which generally showed positive anomalies. This general picture is modified by various local factors, such as cold ocean currents, monsoon activity and cyclone formation areas. Global modes of climate variability, such as the El Niño‐Southern Oscillation (ENSO) and the Madden‐Julian Oscillation (MJO), affect the variability of precipitation either directly or by modifying other relevant atmospheric and oceanic processes. Their influence is seen in many areas with higher‐than‐normal variability and is especially true if the high variability is accompanied by large amounts of mean annual precipitation. The authors believe that the present methodology may be useful in assessing the quality of future global data sets. It is, however, very desirable that such data sets include interpolation error estimates. Copyright © 2012 Royal Meteorological Society

Datos climáticos históricos para las regiones españolas. CRU TS 2.1

Our work translates the global data base of the University of East Anglia Climate Research Unit (http://www.cru.uea.ac.uk/), known as CRU TS 2.1, into regional data for Spain at two levels: autonomous communities (Comunidades Autónomas, NUTS 2) and provinces (NUTS 3).The original data base, which is in grid form, is not suitable for social scientists and historians for two reasons. On the one hand, they are not yet familiar with the new Geographical Information Systems (GIS) technology which is necessary for handling this type of data structure. On the other hand, and more importantly, GIS data in grid form cannot be directly combined with the data usually available to these researchers.This transformation makes it possible to perform two tasks. We can compare this data base directly with statistics from meteorological stations and examine the consistency between data sources. In addition, we can combine the transformed data base with demographic and socioeconomic data normally available only in formats that depend on a country's administrative and political structure.

Relevance, impact and academic spin

Ideally, collective judgements about the development of cleaner technologies should be based on a complete and objective assessment of all the relevant and well-founded evidence. In reality, of course, this will not be possible as the evidence will be partial and incomplete and any assessment of it will be skewed by the interests, motivations and perspectives of those doing the assessing. Increasingly important to governmental, institutional and business decision-making in the transition to more sustainable ways of living are the attitudes of the wider public and their expression through the political process, informed, influenced or determined (take your pick) by the press, radio, television and the internet. While these influences are not wholly negative, the methods of the media increasingly affect the way science is published, promoted and presented. I am not primarily concerned with the more obvious and egregious instances, such as the use of the media to make early disclosure of (non-peer-reviewed) experimental results that point to some major scientific breakthrough or matter of great social importance. The use of a press conference to present data from Pons (University of Utah) and Fleischmann (University of Southampton) believed to provide evidence of the phenomenon called ‘cold-fusion’ was followed by a major scientific debate that centred not just on the observations and their interpretation, but on the appropriateness of pre-empting the standard procedures of manuscript submission and peer-review. This was science in its proper self-correcting mode. Nor am I primarily concerned with ‘Climategate’ (nor even its sequel, ‘Glaciergate’). The Intergovernmental Panel on Climate Change (IPCC 2007) has compiled and presented various summaries of the current (imperfect) state of knowledge that have been broadly accepted by fellow scientists (not, of course, without well-founded criticism and open-minded scepticism). This success is all the more remarkable because of the powerful intellects (I will not say inflated egos!) and heavy-weight disputation that characterise scientific discourse even in a single discipline, let alone across and between so many disciplines concerned with highly complex questions. Attempts to undermine these efforts prior to the UN climate change conference in Copenhagen in December 2009 led to ‘Climategate’, the media furore resulting from the theft and publication of e-mails and other material from the University of East Anglia Climate Research Unit. Increased scepticism of the lay public towards evidence for man-made impact on the world’s climate appears to have resulted. My own view is that such scepticism is likely to be temporary (and unlikely to turn to scepticism’s more virulent and destructive cousin, denialism), if a balanced view of the scientific evidence continues to be provided. There may, indeed, be some positive benefits from this affair: it may serve to underline, first that scientists are human after all, and second that important uncertainties in aspects of climate change science and its possible consequences (highlighted by sceptics) do remain to be resolved (Schiermeier 2010). Much of the criticism of the scientists concerned exploited the use of the word ‘trick’ to characterise a means of presenting data. In a scientific context, ‘trick’ is often used to describe a clever means of resolving a technical problem and does not have the pejorative meaning, used more widely, that of an underhand and deceitful action. That much of the Climategate controversy revolved around something as seemingly N. Winterton (&) Department of Chemistry, University of Liverpool, Liverpool L69 7ZD, UK e-mail: N.Winterton@liverpool.ac.uk

Hemispheric asymmetry of surface temperature anomalies

In recent months there has been some controversy concerning the possible effect of suspended sulfate aerosols on warming trends predicted to occur in response to steadily increasing greenhouse gas concentrations in the troposphere. Evidence in the recent literature both supporting and doubting the theory that aerosols have suppressed warming in the Northern Hemisphere more than in the Southern Hemisphere has relied on analyses of radiosonde observations covering various periods between 1958 and 1995. In this letter the UK Met Office/University of East Anglia Climatic Research Unit (Parker/Jones) data sets of mean surface temperature anomalies over land and sea for the past 140 years serve as an independent data base to test earlier reported results obtained from radiosonde observations. The results suggest that there is no evidence of any systematic differences in temperature trends between the two hemispheres.

Holocene book reviews: Future climate change and radioactive waste disposal Edited by C.M. Goodess and J.P. Palutikof, 1991. Norwich: University of East Anglia Climatic Research Unit, 261 pp., softcover

Holocene book reviews: Future climate change and radioactive waste disposal Edited by C.M. Goodess and J.P. Palutikof, 1991. Norwich: University of East Anglia Climatic Research Unit, 261 pp., softcover

Interhemispheric contrasts of mean global temperature anomalies

AbstractNorthern and Southern Hemisphere series of surface temperature anomalies are compared. The series studied are the University of East Anglia Climatic Research Unit (CRU) monthly series (1854–1986) and the UK Meteorological Office (MO) quarterly series (1856–1989). A major difference is the marked seasonal variation of the warming trend in the Northern Hemisphere, with maximum in winter and minimum in summer. Analysis of the annual cycle of the CRU set suggests a shift in phase of the warm peak in the annual cycle of temperature anomalies from July to January for the period. This shift is a characteristic of the annual cycle itself and does not have to be associated with a greater warming trend in winter than in summer, although it may be.The series were converted into interannual differences from one month or quarter to the corresponding month or quarter in the following year. Globally, the sequential values of the positive and negative modes of the interannual differences suggest a slow relaxation towards zero with the absolute values of the interannual coolings decreasing faster than those of the interannual warmings. Spectral analyses of the first‐order interannual differences of the monthly CRU and of the quarterly MO series suggest that the temperature field reacts to a Quasi‐Biennial Oscillation pulse in the Northern Hemisphere and to a stronger ENSO pulse in the Southern Hemisphere.