中国极端天气气候研究——“地球系统与全球变化”重点专项项目简介及最新进展

全球变暖背景下,极端天气气候事件频发,并表现出群发性、持续性、复合性等特点,不可预测性增加;持续性强降水、极端低温、复合型极端高温干旱、群发性热浪和台风等极端天气气候事件对我国经济社会和可持续发展影响巨大。然而,上述极端天气气候事件的新特征、关键过程和机理尚不完全清楚,重大极端事件的预报预测水平亟待提升。文章首先简要介绍“地球系统与全球变化”重点专项项目“中国极端天气气候事件的形成机理及其预测和归因”的基本情况。项目拟在分析全球变化背景下对我国造成重大影响的极端天气气候事件新特征的基础上,深入研究多尺度海-陆-气耦合过程影响极端天气气候事件的机理,挖掘极端天气气候事件次季节-季节预测的前兆信号;发展动力与物理统计相结合的极端事件预测新方法,研制针对中国极端事件的新一代高分辨率数值预报与检测归因系统。文章重点总结了自2022年12月项目立项至今取得的最新研究成果和进展。     

A Review of Climate Change Attribution Studies

This paper reviews recent progress in climate change attribution studies. The focus is on the attribution of observed long-term changes in surface temperature, precipitation, circulation, and extremes, as well as that of specific extreme weather and climate events. Based on new methods and better models and observations, the latest studies further verify the conclusions on climate change attribution in the IPCC AR5, and enrich the evidence for anthropogenic influences on weather and climate variables and extremes. The uncertainty of global temperature change attributable to anthropogenic forcings lies in the considerable uncertainty of estimated total radiative forcing due to aerosols, while the uncertainty of precipitation change attribution arises from the limitations of observation and model simulations along with influences from large internal variability. In terms of extreme weather and climate events, it is clear that attribution studies have provided important new insights into the changes in the intensity or frequency of some of these events caused by anthropogenic climate change. The framing of the research question, the methods selected, and the model and statistical methods used all have influences on the results and conclusions drawn in an event attribution study. Overall, attribution studies in China remain inadequate because of limited research focus and the complexity of the monsoon climate in East Asia. Attribution research in China has focused mainly on changes or events related to temperature, such as the attribution of changes in mean and extreme temperature and individual heat wave events. Some progress has also been made regarding the pattern of changes in precipitation and individual extreme rainfall events in China. Nonetheless, gaps remain with respect to the attribution of changes in extreme precipitation, circulation, and drought, as well as to the event attribution such as those related to drought and tropical cyclones. It can be expected that, with the continual development of climate models, ongoing improvements to data, and the introduction of new methods in the future, climate change attribution research will develop accordingly. Additionally, further improvement in climate change attribution will facilitate the development of operational attribution systems for extreme events, as well as attribution studies of climate change impacts.     

Is Strange Weather in the Air? A Study of U.S. National Network News Coverage of Extreme Weather Events

This paper asks whether extreme weather events are becoming more discernible. It uses the Vanderbilt University Television News Archives to determine if annual coverage given to heat waves, droughts, hurricanes and floods has increased on the network news between 1968 and 1996. An index of extreme weather events shows a clear trend toward increased coverage, especially since 1988. However, the different types of extreme events do not receive equal coverage: for example, annual peaks for droughts contain about twice as many stories as the peaks for heat waves. The data further reveal that there is no association between coverage of climate change and the overall coverage of extreme events. While extreme events have attracted more stories in the U.S., there has been no increase in the coverage devoted to extreme events in foreign countries. The possible effects of shifts in TV coverage on the public salience and understanding of climate change are discussed.     

Potential hydrometeorological threshold values of the coastal hazard—an example from the Polish Southern Baltic coast

This paper analyses the spatiotemporal variability of extreme hydrometeorological events at the Polish coast of the Baltic Sea. Extreme precipitation events and storm surges determine to the largest extent the contemporary transformations of sea coastal geoecosystems and represent the major factors that disturb their functioning. The statistical characteristics of these values were computed from the data of six meteorological and tide-gage stations located at the Baltic seaside. Daily data on the amount of precipitation and the sea level for the period of 1966–2009 were used for the study. Annual and daily maximum values of precipitation and sea level are presented for the Southern Baltic coast. The threshold values of the hydrometeorological parameters considered in the study allow assessing the hazard caused by the disturbance of the functional stability of the sea coastal geoecosystems.     

Tropical cyclone contribution to extreme rainfall over southwest Pacific Island nations

Southwest Pacific nations are among some of the worst impacted and most vulnerable globally in terms of tropical cyclone (TC)-induced flooding and accompanying risks. This study objectively quantifies the fractional contribution of TCs to extreme rainfall (hereafter, TC contributions) in the context of climate variability and change. We show that TC contributions to extreme rainfall are substantially enhanced during active phases of the Madden–Julian Oscillation and by El Niño conditions (particularly over the eastern southwest Pacific region); this enhancement is primarily attributed to increased TC activity during these event periods. There are also indications of increasing intensities of TC-induced extreme rainfall events over the past few decades. A key part of this work involves development of sophisticated Bayesian regression models for individual island nations in order to better understand the synergistic relationships between TC-induced extreme rainfall and combinations of various climatic drivers that modulate the relationship. Such models are found to be very useful for not only assessing probabilities of TC- and non-TC induced extreme rainfall events but also evaluating probabilities of extreme rainfall for cases with different underlying climatic conditions. For example, TC-induced extreme rainfall probability over Samoa can vary from ~ 95 to ~ 75% during a La Niña period, if it coincides with an active or inactive phase of the MJO, and can be reduced to ~ 30% during a combination of El Niño period and inactive phase of the MJO. Several other such cases have been assessed for different island nations, providing information that have potentially important implications for planning and preparing for TC risks in vulnerable Pacific Island nations.

     

中国生态脆弱区高温热浪和干旱历史变化特征分析北大核心CSCD

高温热浪和干旱是影响陆地生态系统最主要的极端天气气候事件。已有关于中国高温热浪和干旱历史变化的定量研究主要针对全国范围、地理分区或单一区域,对于我国生态脆弱区相关极端事件的历史变化特征尚不清楚。本文利用中国CN05.1格点化观测数据集中的日最高气温观测资料和全球逐月标准化降水蒸发指数格点数据,分析了中国典型生态脆弱区1980~2014年发生的高温热浪和干旱的时空变化特征。结果表明:1980~2014年中国生态脆弱区的年高温日数和热浪次数整体呈增加趋势,两者变化趋势的空间分布类似。在空间分布上,高温热浪显著增加的区域主要位于北方生态脆弱区的中部和西部以及南方生态脆弱区的东部。其中,高温热浪增长显著的面积比率在西南岩溶山地石漠化脆弱区最高,在南方农牧脆弱区最低。区域平均来看,除南方农牧脆弱区较少发生高温热浪外,各脆弱区高温日数和热浪次数均呈现增加趋势,且除北方农牧林草区外,其余脆弱区增加趋势显著。北方生态脆弱区高温和热浪的发生频率和年际变化在20世纪90年代中期起均迅速增加。此外,中国生态脆弱区东部多呈现变干趋势且中等和极端干旱发生月数增多,其余地区则多变湿且极端干旱发生月数减少;区域平均来看,除西南岩溶山地石漠化脆弱区区域平均的干旱发生月数呈现显著增加趋势以外,其他区域的干湿和干旱发生月数的变化趋势小且不显著。     

Critical analysis of simulated daily temperature data from the ARPEGE-climate model: application to climate change in the Champagne wine-producing region

As global warming is scientifically and widely accepted, its impacts at regional scales are raising many questions for wine producers. In particular, climate parameters, especially temperature, play a decisive role in vine growth and grape ripening. An overview of expected climate change in terms of bioclimatic indexes (Winkler and Huglin) and thermal extremes in the wine-producing region of Champagne is presented. A variable-grid atmospheric general circulation model, ARPEGE-Climate, with a local zoom at 50 km over the area of interest, is used to investigate potential future changes in thermal extremes and bioclimatic indexes. Changes in daily maximum and minimum temperatures at key stages are discussed for three emission scenarios (B1, A1B, A2) that are currently used in studies of impacts of climate change. Model outputs are analyzed and critically assessed for a control period (1971–2000) and for changes in extreme events in relation to future scenarios, such as a decrease in extreme low temperatures in spring (April) during bud break and an increase in extreme high temperatures in summer, associated with more frequent heat waves during ripening.     

Occurence Frequency of Storm Wind Waves in the Baltic,Black, and Caspian Seas under Changing Climate Conditions

The article proposes the method of climatic forecast of the occurrence frequency of synoptic conditions causing severe hydrometeorological events as well as severe events that are genetically related to them, in particular, storm wind waves. The choice of sea level pressure field as an indicator of atmospheric conditions of storm waves is substantiated. The algorithm for the method implementation is developed. It includes the processing of observational/reanalysis data; wind wave simulation; the systematization of synoptic conditions that accompany storm waves under the modern climate; the assessment of the ability of climate models of atmospheric and oceanic general circulation to simulate correctly the frequency of the revealed types of synoptic conditions for the modern climate; and the forecast of the frequency of these types for the possible scenarios of the future climate.     

ENSO,the IOD and the intraseasonal prediction of heat extremes across Australia using POAMA-2

The simulation and prediction of extreme heat over Australia on intraseasonal timescales in association with the El Niño–Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) is assessed using the Bureau of Meteorology’s Predictive Ocean Atmosphere Model for Australia (POAMA). The analysis is based on hindcasts over 1981–2010 and focuses on weeks 2 and 3 of the forecasts, i.e. beyond a typical weather forecast. POAMA simulates the observed increased probabilities of extreme heat during El Niño events, focussed over south eastern and southern Australia in SON and over northern Australia in DJF, and the decreased probabilities of extreme heat during La Niña events, although the magnitude of these relationships is smaller than observed. POAMA also captures the signal of increased probabilities of extreme heat during positive phases of the IOD across southern Australia in SON and over Western Australia in JJA, but again underestimates the strength of the relationship. Shortcomings in the simulation of extreme heat in association with ENSO and the IOD over southern Australia may be linked to deficiencies in the teleconnection with Indian Ocean SSTs. Forecast skill for intraseasonal episodes of extreme heat is assessed using the Symmetric Extremal Dependence Index. Skill is highest over northern Australia in MAM and JJA and over south-eastern and eastern Australia in JJA and SON, whereas skill is generally poor over south-west Western Australia. Results show there are windows of forecast opportunity related to the state of ENSO and the IOD, where the skill in predicting extreme temperatures over certain regions is increased.     

Summer heat waves over western Turkey between 1965 and 2006

Global warming is one of the greatest environmental, economic, and social threats in the world. There are many assessments to estimate climate variability over many regions. A change in the Earth’s surface temperature leads to increase in extreme temperature events, which are harmful to the ecosystem, and moreover, they create danger on human health. In this study, we have selected the western part of Turkey as the study area, since climate change projections for Turkey point out that the highest temperature change can be expected on this region during summer, and the Turkish population is very dense here to be affected by extreme events. We have used apparent temperatures to define the heat waves which we have determined their frequencies for the summer months (June–August) of 1965–2006. Since the regional comparisons of station results are intended, we selected the 90th percentile value for each station as a threshold value to be used in the delineation of heat waves. Then, the number of heat waves is determined by imposing the constraint that apparent temperatures stay above the threshold value at least for three consecutive days. Then, the changes in the number of hot days and heat waves and also their durations are analyzed by using the linear least square method. We have found that the number of hot days, heat waves, and heat wave durations is increased between 1965 and 2006 on the western part of Turkey. Additionally, their rate of change is larger within the last decade and extremes are frequently observed after 1998. Regional distributions show that the tendency of the number of heat wave events increases towards the southern latitudes of the domain. Moreover, we investigated the relationship between the number of hot days and the sea surface temperatures of the Mediterranean Sea and Black Sea. Correlation analyses are carried out by the number of hot days and averaged sea surface temperatures on the regions of the western, central, and eastern Mediterranean Sea and the Black Sea. It is found that the number of hot days of west Turkey is better correlated with the sea surface temperatures averaged over eastern Mediterranean and Black Seas. The number of heat waves is found significantly correlated with the fire occurrences for most of the stations.     

全球和中国区域近50年气候变化检测归因研究进展

回顾了近年来国内外对全球和中国区域气候变化的检测归因研究,主要集中在对20世纪中期以来温度、降水和主要极端事件变化的检测归因研究进展,而不涉及更长时间尺度历史气候变化的检测归因。分析表明,国际上近年来在气候变化检测归因研究领域发展迅速,从全球尺度气温变化的检测归因发展到区域尺度和多变量的检测归因。但在中国,虽然也有一些研究探讨了中国东部南涝北旱等发生的原因,但在以数理统计推断方法为基础的气候变化事实归因领域的研究仍然亟待加强。一些重要的问题,如中国不同区域的变暖、不同区域的变干或变湿的归因分析,以及这些因子和引起全球气候变化因子的异同等,都是迫切需要回答的科学问题。     

Blaming climate change? How Indian mainstream media covered two extreme weather events in 2015

Reporting the links (or lack of them) between human-induced climate change and individual extreme weather events poses a series of challenges for journalists. In recent years, their task has become more complicated by the increase in the number of extreme event attribution (EEA) studies which assess how climate change is affecting the intensity or likelihood of specific weather events. Such studies are complex, contain uncertainties, and can be difficult to explain to a lay audience. Previous scholarship has largely focused on media coverage of extreme events in developed countries, and on the volume of coverage of the links to climate change, without examining references to EEA studies. To help fill this gap, we take India as our case study, and the mainstream media coverage there of the Chennai rainfall event and the heat wave in Andhra Pradesh in 2015. Both events were subject to attribution studies. Amongst our findings are that journalists most commonly used generic phrases to describe the link between such events and climate change; politicians and NGOs often ‘blamed’ climate change without reference to the science; and relevant EEA studies were seldom quoted. Based on our findings, we make some preliminary recommendations for training journalists in India and elsewhere to support accurate reporting of extreme events and their possible linkages to climate change.     

Projected Heat Wave Characteristics over the Korean Peninsula During the Twenty-First Century

Climate change is expected to increase temperatures globally, and consequently more frequent, longer, and hotter heat waves are likely to occur. Ambiguity in defining heat waves appropriately makes it difficult to compare changes in heat wave events over time. This study provides a quantitative definition of a heat wave and makes probabilistic heat wave projections for the Korean Peninsula under two global warming scenarios. Changes to heat waves under global warming are investigated using the representative concentration pathway 4.5 (RCP4.5) and 8.5 (RCP8.5) experiments from 30 coupled models participating in phase five of the Coupled Model Inter-comparison Project. Probabilistic climate projections from multi-model ensembles have been constructed using both simple and weighted averaging. Results from both methods are similar and show that heat waves will be more intense, frequent, and longer lasting. These trends are more apparent under the RCP8.5 scenario as compared to the RCP4.5 scenario. Under the RCP8.5 scenario, typical heat waves are projected to become stronger than any heat wave experienced in the recent measurement record. Furthermore, under this scenario, it cannot be ruled out that Korea will experience heat wave conditions spanning almost an entire summer before the end of the 21st century.     

Objective probabilities about future climate are a matter of opinion

In this paper, the unfeasibility of producing “objective” probabilistic climate change scenarios is discussed. Realizing that the knowledge of “true” probabilities of the different scenarios and temperature changes is unachievable, the objective must be to find the probabilities that are the most consistent with what our state of knowledge and expert judgment are. Therefore, subjective information plays, and should play, a crucial role. A new methodology, based on the Principle of Maximum Entropy, is proposed for constructing probabilistic climate change scenarios when only partial information is available. The objective is to produce relevant information for decision-making according to different agents’ judgment and subjective beliefs. These estimates have desirable properties such as: they are the least biased estimate possible on the available information; maximize the uncertainty (entropy) subject to the partial information that is given; The maximum entropy distribution assigns a positive probability to every event that is not excluded by the given information; no possibility is ignored. The probabilities obtained in this manner are the best predictions possible with the state of knowledge and subjective information that is available. This methodology allows distinguishing between reckless and cautious positions regarding the climate change threat.     

Modelling probability of rainfall-induced shallow landslides in a changing climate, Otta, Central Norway

We analyse slope stability conditions for shallow landslides under an extreme precipitation regime with regard to present and future scenarios, in order to first study the effect of changes in precipitation on stability conditions, considering uncertainty in the model parameters, and second to evaluate which factors contribute the most to model output and uncertainty. We used a coupled hydrological-stability model to study the hydrological control on shallow landslides in different precipitation regimes, with reference to the case study of Otta, located in central east Norway. We included a wide range of climatic settings, taking intensity, duration of the extreme events and two different antecedent precipitation conditions into account. Eleven future scenarios were determined using results of down-scaled meteorological models. Considering the uncertainty in the soil parameters, we used the Monte Carlo approach and probability of failure resulting from 5,000 trials was calculated for each precipitation scenario. In unstable areas the probabilities of failure at present and future conditions were compared using a bootstrapping method. Sensitivity analysis was carried out to understand how variations in input parameters influence the output of the selected model. The results show changes in the modelled stability conditions only if the effect of antecedent precipitation is not taken into account. The uncertainties in the predicted extreme precipitation events, soil parameters, and antecedent precipitation conditions do not allow any accurate estimation of changes in stability conditions for shallow landslides.     

陕西关中及周边地区近500a来初夏旱涝事件初步分析

基于华山树轮宽度差值年表重建的陕西关中及周边地区近500a来的初夏干燥指数序列,对该地区初夏极端旱涝事件及其连续旱涝变化特征进行了初步分析.区域干燥指数与Palmer指数在变化上极为相似,可用于反映该地区的旱涝变化.结果表明:该地区近500a来初夏共发生18次极端干旱事件和11次极端洪涝事件,除公元1521年与历史文献记录的旱涝事件相反,公元1513年、1574年、1675年和1945年未发现历史记录外,其余年份均能找到相应记录;近500a来初夏存在9个显著的连续偏旱期和10个显著的连续偏涝期,并以16和19世纪发生的连续旱涝事件最为频繁,而17和18世纪发生的旱涝事件相对较少,20世纪发生的干旱事件明显多于洪涝事件.     

Simulation of the probable maximum flood in the area of the Leningrad Nuclear Power Plant with account of wind waves

At the designing of nuclear power facilities at the coastal sites the risk of their flooding caused by the combinations of adverse hydrometeorological events should be assessed with the probability of exceedance to 0.01%. According to the IAEA recommendations, the combination of statistical and deterministic methods was used to calculate the flood level of such rare occurrence. The level of flooding caused by the storm surge and reiated wind waves were computed with the probability of 0.01% for the coastal part of the Koporye Bay of the Gulf of Finland in the area of the Leningrad Nuclear Power Plant 2 (LNPP 2) construction; the results are presented. The calculations are based on the CARDINAL and SWAN software and four nested numerical models (for the Baltic Sea, the eastern part of the Gulf of Finland, the Koporye Bay, and a part of the bay in the area of LNPP). The decrease in sea-surface drag coefficient at hurricane winds is taken into account.     

Natural variability or climate change? Stakeholder and citizen perceptions of extreme event attribution

Scientists can now connect extreme weather events with climate change using a methodology known as “extreme event attribution”, or EEA. The idea of connecting climate change and extreme weather has long been heralded as a panacea for communications, connecting the dangers of climate change to real-world, on-the-ground events. However, event attribution remains a nascent science, and attribution studies of the same event can sometimes produce divergent answers due to precise methodology used, variables examined, and the timescale selected for the event. The 2011–2017 California drought was assessed by 11 EEA studies which came to varying conclusions on its connection to climate change. This article uses the case study of the drought and a multi-methods approach to examine perceptions of EEA among key stakeholders and citizens. Twenty-five key informant interviews were conducted with different stakeholders: scientists performing EEA research, journalists, local and state-level policymakers, and non-governmental organization representatives. In addition, two focus groups with 20 California citizens were convened: one with environmentalists and another with agriculturalists. While climate change was viewed by many as a mild contributing factor to the California drought, many stakeholders had not heard of EEA or doubted that scientists could conclusively link the drought to anthropogenic climate change; those that were familiar with EEA felt that the science was generally uncertain. In the focus groups, presentation of divergent EEA results led participants to revert to pre-existing ideas about the drought-climate connection, or to question whether science had sufficiently advanced to analyze the event properly. These results indicate that while EEA continues to provoke interest and research in the scientific community, it is not currently utilized by many stakeholders, and may entrench the public in pre-existing views.     

海洋和冰冻圈变化有关的极端事件、突变及其影响与风险

《气候变化中的海洋和冰冻圈特别报告》（SROCC）于2019年9月在IPCC第一工作组和第二工作组第二次联合大会上得到审议通过,并得到了IPCC第51届全会接受和批准。文中主要对该报告中海洋和冰冻圈变化有关的极端事件、突变及其影响与风险的有关评估内容进行了综合分析。SROCC评估得到的最新结果显示：气候变化背景下冰冻圈变化引起的山体滑坡、雪崩和冰川洪水事件频发。海洋有关的海洋热浪频发,极端El Niño事件加强,大西洋经向翻转环流减弱。同时,沿海地区极端海平面上升,极端海浪增高,极端热带气旋影响增加。这些变化,比如海洋热浪等,是可以归因于人为增暖的。预估结果表明,海洋和冰冻圈变化引起的极端事件未来会进一步加剧。而这些变化已经影响了高山、极地以及沿海地区人群的生产和生活,以及海洋和冰冻圈的生态系统服务功能。应对这一系列变化,需要更加精准的预测和预警,包括对极端事件和突变的季节预测和年际、年代际预测,以便做好充足的准备来降低极端事件风险。同时,加强应对极端事件的科普教育和提供因地制宜的灾害重建措施等也是风险管理的重要环节。     

The contribution of urbanization to recent extreme heat events and a potential mitigation strategy in the Beijing–Tianjin–Hebei metropolitan area

This paper addresses the contribution of urban land use change to near-surface air temperature during the summer extreme heat events of the early twenty-first century in the Beijing–Tianjin–Hebei metropolitan area. This study uses the Weather Research Forecasting model with a single urban canopy model and the newest actual urban cover datasets. The results show that urban land use characteristics that have evolved over the past ~20 years in the Beijing–Tianjin–Hebei metropolitan area have had a significant impact on the extreme temperatures occurring during extreme heat events. Simulations show that new urban development has caused an intensification and expansion of the areas experiencing extreme heat waves with an average increase in temperature of approximately 0.60 °C. This change is most obvious at night with an increase up to 0.95 °C, for which the total contribution of anthropogenic heat is 34 %. We also simulate the effects of geo-engineering strategies increasing the albedo of urban roofs, an effective way of reducing urban heat island, which can reduce the urban mean temperature by approximately 0.51 °C and counter approximately 80 % of the heat wave results from urban sprawl during the last 20 years.