Climate Change Theme

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  • 1  Dependence of climate feedbacks on temperature patterns:interpreting IPCC AR6
    WANG Fei ZHANG Hua LIU Mengting YU Xiaochao ZHAO Shuyun
    2022, 45(6):826-834. DOI: 10.13878/j.cnki.dqkxxb.20220928001
    [Abstract](315) [HTML](275) [PDF 4.10 M](1335)
    Based on the content of Chapter 7 from the Sixth Assessment Report (AR6) contributed by the Intergovernmental Panel on Climate Change (IPCC) Working Group I (WGI),this paper interprets the dependence of climate feedbacks on temperature patterns in detail.Compared with the Fifth Assessment Report (AR5),the understanding of the relationship between transient changes in climate feedback and evolving spatial patterns of surface temperature has been greatly improved in AR6.The assessments show that under greenhouse gas forcing,it is very likely that the warming in the Arctic will be more pronounced than on global average over the 21st century.On centennial timescales,the Antarctic will warm more than the tropics and the tropical Pacific Ocean east-west sea surface temperature (SST) gradient will weaken,with greater warming in the east than the west.AR6 identifies changes in the degree of polar amplification over time,particularly in the Southern Hemisphere,and changes in the tropical Pacific Ocean east-west SST gradient over time as key factors affecting how climate feedbacks may evolve in the future.Climate feedbacks,particularly from clouds,are expected to become less negative (more amplifying) on multi-decadal timescales as the spatial pattern of surface warming evolves.
    2  Understandings of assessment reports on climate change impacts,adaptation and vulnerability:progress from IPCC AR5 to AR6
    JIANG Tong ZHAI Jianqing LUO Yong SU Buda CHAO Qingchen WANG Yanjun WANG Guojie HUANG Jinlong XU Runhong GAO Miaoni MIAO Lijuan
    2022, 45(4):502-511. DOI: 10.13878/j.cnki.dqkxxb.20220529013
    [Abstract](881) [HTML](1411) [PDF 29.68 M](9510)
    The second working group of the IPCC Sixth Assessment Report (IPCC AR6 WGⅡ) focuses on the impact,risk,adaptation and vulnerability of climate change.The report quantitatively assesses the impact of climate change on natural and human systems with the latest data,detailed evidence and diverse methods.Compared to AR5,the following progress has been made:Firstly,The content clarifies that the impact of climate change is attributable to three categories:anthropogenic climate forcing,non-climate factor action and weather sensitivity identification,127 key risks from climate change will become widespread or irreversible,and limiting global warming to 1.5 ℃ can greatly reduce climate change loss and damage to natural and human systems,pointing to the importance of adapting to transition.Secondly,AR6 WGⅡ adopts the latest combination of SSPs and RCPS in terms of evaluation method,which is more comprehensive.Thirdly,AR6 WGⅡ has focus on risks and solutions,and on the basis of AR5 WGⅡ,it is clarified that under different future warming scenarios,the risk level of the key risks facing the five “reasons for concern (RFCs)” will be relied on lower to very high levels of global warming.Finally,AR6 WGⅡ clarifies the urgency of climate action,combining adaptation and mitigation to support sustainable development is essential for climate resilience development pathways,pointing to the importance of immediate action to address climate risks.
    3  Climate change and marine ecosystems: impacts, adaptation, and vulnerability
    TAN Hongjian CAI Rongshuo DU Jianguo HU Wenjia
    2022, 45(4):489-501. DOI: 10.13878/j.cnki.dqkxxb.20220411001
    [Abstract](898) [HTML](2960) [PDF 9.18 M](1650)
    In this report,the IPCC Working Group Ⅱ's contribution to the Sixth Assessment Report Chapter 3 presents an assessment of the impacts of climate change on the ocean and coastal ecosystems,along with their vulnerability and the potential adaptation solutions.This report clarifies the fact that the anthropogenic greenhouse gases have and will continue to cause fundamental changes to the physical and chemical properties of our centrally important oceans,including warming,sea level rise (SLR),acidification,deoxygenation,and change in nutrients.The occurrences of the marine heatwaves have doubled since the 1980s,and will become 4-8 times more frequent in 2081—2100 compared to 1995—2014.In addition,ocean warming since the 1950s has shifted marine species poleward,at an average of 59.2±15.5 km per decade.This has resulted in reduced biomass in tropical waters,a remarkable tropicalization of mid-latitude ocean,and an earlier phytoplankton growth period in polar and sub-polar areas.Marine heatwaves are exposing species,and ecosystems approach or even exceed their tolerance,causing mass coral bleaching and mortality,and loss of seagrasses and kelp forests.Warming,acidification and hypoxia have collectively resulted in changes in the community structure and increases in the occurrence of harmful algal blooms in estuaries,and have contributed to an overall decline in phytoplankton biomass and primary production.In the meantime,phytoplankton biomass in the polar ocean will increase.Accelerating SLR has led to the degradation of coastal wetland ecosystems (e.g.,mangroves,saltmarshes and seagrass beds).Ocean conditions are projected to continue and increase risk of regional extirpations and global extinctions of marine species,especially near the Equator and in the Arctic.Coral reefs are projected to decline by a further 70%—90% at 1.5 ℃ warming with greater losses (>99%) at 2 ℃,as early as the 2040s under SSP5-8.5.The current available adaptation options (e.g.,marine protected areas and mangrove restoration) are unable to offset the growing climate-change risk,thus exemplifying the need for transformative climate adaptation and ambitious mitigation measures.
    4  Most recent understanding of key risks across sectors and regions of climate change: interpreting IPCC AR6 WGⅡ
    GAO Miaoni ZHAI Jianqing CHEN Ziyan LIN Qigen HUANG Jinlong LIU Shuci JIANG Tong
    2022, 45(4):530-538. DOI: 10.13878/j.cnki.dqkxxb.20220518011
    [Abstract](456) [HTML](372) [PDF 39.72 M](1669)
    The chapter of Working Group Ⅱ Contribution to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR6 WGⅡ) entitled,“Key Risks Across Sectors and Regions”,synthesizes observed climate change impacts,adaptation-related responses,limits to adaptation,and the key risks identified across sectors and regions.Compared to AR5,AR6 WGⅡ provides additional and stronger evidence for impacts of climate change;emphasizes the effect of adaptation to reducing risk;differentiates soft and hard limits to adaptation;raises the concept of residual risk in the conceptual framework of risk evaluation;and updates the dependence of risk associated with the Reasons for Concern on the level of climate change.The impacts of changes in climate-related systems have been identified in a wide range of natural,human,and managed systems (very high confidence).The responses in ecosystems may not be adaptive enough or sufficient to cope with the rate of climate changes (high confidence).There is negligible evidence that adaptation in human systems is adequate to reduce climate risk (high confidence).Maladaptation is increasing (high confidence).Limits to adaptation stem from interactions between soft and hard limits (high confidence).The report of AR6 WGⅡ identified 127 Key Risks and risk cascades,which will enhance eight Representative Key Risks across sectors and regions to a certain extent.Representative Key Risks increase the challenges in achieving global sustainability goals (high confidence).Increasing evidence now supports the five major Reasons for Concern regarding climate change.Assuming low to no adaptation,risks for all five Reasons for Concern increase to high and very high levels under global warming (high confidence).
    5  The impacts of climate change on human health:interpretation of IPCC AR6 WGⅡ
    WANG Yanjun WANG Dongfang GAO Miaoni SHAN Jingjing SU Buda
    2022, 45(4):520-529. DOI: 10.13878/j.cnki.dqkxxb.20220508011
    [Abstract](507) [HTML](953) [PDF 24.49 M](1667)
    Chapter 7 of the IPCC Sixth Assessment Report (AR6),Working Group II (WG II),entitled'Health,well-being and the changing structure of communities’,assessed the current impacts and projected risks of climate change on health and well-being,and proposed strategies and constraints for health adaptation.Evidence has increased since AR5 that climate change has had negative impacts on human physical health,including mental health,through direct or indirect way,and that climate-sensitive diseases,malnutrition,premature death,and threats to mental health are increasing,and that climate-related hazards are increasingly affecting a growing number of health outcomes (including communicable and non-communicable diseases) and geographical areas.Cascading and compounding risks affecting health due to extreme weather events have been observed in all regions and risks are expected to increase with further warming.Key adaptation measures for health risks include increasing investment in health and other systems,strengthening integration and collaboration across sectors and systems,building climate-resilient development pathways,and integrating adaptation and mitigation in the goal of sustainable development and so on,which will bring huge co-benefits for health and well-being.
    6  New perceptions and trends in impacts and adaptations of food systems in IPCC AR6
    JU Hui YUAN Jiashuang ZHANG Xinyue LIU Zhongwei WANG Jiandong
    2022, 45(4):481-488. DOI: 10.13878/j.cnki.dqkxxb.20220330007
    [Abstract](910) [HTML](412) [PDF 872.09 K](1426)
    Interpreting the impacts and adaptations of food systems in the Sixth Assessment Report (AR6) of the Intergovernmental Panel on Climate Change (IPCC) Working Group II (WGII) is important for the scientific understanding of the frontiers of the international discipline of climate change impacts on agriculture.The newly released IPCC AR6,on the basis of further elaboration of food production capacity,planting layout,pest and disease impacts,further confirms the negative impacts of anthropogenic warming on food systems,discusses climate risks in food processing,transportation and consumption,extends the review of food impacts in complex ecosystems,and expands the analysis of climate change impacts on the entire chain of food production-processing-transportation-consumption.It extends the attribution of impacts and enriches the scientific understanding of agro-environmental impacts.As for the adaptation capacity of food systems,it emphasizes the development pathway of climate resilience based on the synergy of adaptation and mitigation,the adaptation assessment has gradually shifted from the theoretical aspects of adaptation capacity and adaptation methods to the assessment of adaptation implementation and effectiveness,and the regional specificity and effectiveness of adaptation actions are identified.This assessment emphasizes the detection and attribution of climate change impacts on crops,focuses on the impacts of climate and agro-environmental change,introduces ecosystem-based adaptation schemes and technologies,and assesses the feasibility and effectiveness of existing adaptation technologies.The contents of the report are important references for China to strengthen its capacity in agricultural impact assessment and to catch the international dynamics of the discipline.
    7  Impact attribution of climate change: the new cognition from IPCC AR6 WGⅡ
    SU Buda CHEN Ziyan HUANG Jinlong JIANG Tong
    2022, 45(4):512-519. DOI: 10.13878/j.cnki.dqkxxb.20220425006
    [Abstract](342) [HTML](1293) [PDF 9.20 M](1523)
    Attribution studies include climate change attribution,impact attribution and identification of weather sensitivity.IPCC Sixth Assessment Report Working Group Ⅱ (AR6 WGⅡ) follows the definition of climate change impact attribution in the Fifth Assessment Report Working Group Ⅱ (AR5 WGⅡ),and considers that climate change impact attribution assesses the contribution of climate system changes to observed natural,human or managed system changes.IPCC AR6 WGⅡ sets up a “no-climate change baseline” in the impact attribution studies,and summarizes most recent achievements on the impact attribution of climate change on terrestrial ecosystems,marine ecosystems,coastal systems,water systems,food systems and human society.Compared with the AR5 WGⅡ,the AR6 WGⅡ more specifically describes the impact of climate change on nature,human or managed systems,improves the reliability of some assessment conclusions,and gives more evidence on the social impact of climate change.Although some progresses have been made in climate change impact attribution,the AR6 WGⅡ points out that more high-quality data,more effective methods for quantifying climate change impacts and more comprehensive understanding on the mechanisms of systematic change are still needed to deepen the research on climate change impact attribution.
    8  Latest understanding of extreme weather and climate events under global warming and urbanization influences
    YUAN Yufeng ZHAI Panmao
    2022, 45(2):161-166. DOI: 10.13878/j.cnki.dqkxxb.20211011001
    [Abstract](1351) [HTML](1440) [PDF 784.01 K](1811)
    In recent years, urban climate change has received great attention.This paper synthesizes IPCC AR6 WGI assessment on urbanization influence on extreme weather and climate events in context of global climate change.The new understanding are summarized as follows:Urbanization has exacerbated local warming, thus large cities are facing more severe heat waves;More extreme precipitation events are observed in many urban areas and their downwind direction, resulting in increased surface runoff;Coastal cities are affected by increasing compound flooding related to sea-level rise;Urban pollutant emissions and building structures with unfavorable ventilation have enhanced regional pollution and increased surface ozone concentration.In the future, extreme temperature, extreme precipitation and air pollution are projected to occur more frequently and intensified in cities, thus lead to increased risks of climate change.Considering the rapid progress of China in urbanization, it is necessary to further strengthen observation network, mechanism study and numerical simulation for urban extreme events under global warming, thus to improve our understanding and enhance response capabilities in coping with urban extreme events.
    9  New understandings of the feedback mechanisms in the earth climate system in IPCC AR6
    ZHAO Shuyun KONG Linghan ZHANG Hua WANG Wuke ZHAO Shuyu MA Xinyu WU Danyang
    2021, 44(6):805-817. DOI: 10.13878/j.cnki.dqkxxb.20210920001
    [Abstract](742) [HTML](1308) [PDF 1.32 M](1640)
    Climate feedback reflects the adaptation process of the climate system to external interference, and affects the prediction of future climate change to a great extent.This paper summarizes the content on climate feedback in the Sixth Assessment Report (AR6) of the Intergovernmental Panel on Climate Change (IPCC).In AR6, the understanding of cloud feedback has been improved greatly compared with that in AR5, especiallythe feedback of low clouds over the Subtropical Ocean.The net cloud feedback parameter is assessed to be positive with high confidence in AR6, which plays an amplification effect on climate change..However, the uncertainty range of cloud feedback is still the largest in all feedback mechanisms.Apart from Planck feedback, all the other feedbacks (water vapor, temperature lapse rate, land surface albedo, cloud, bio-geophysical and non-CO2 biogeochemical feedback) are positive or near zero, generally amplifying climate change.The estimate of general climate feedback parameter in AR6 is -1.16 W·m-2·℃-1, with a 5%—95% confidenceinterval of [-1.81, -0.51] W·m-2·℃-1.With global warming, the climate feedback parameters are likely to be closer to the positive value.
    10  Assessment of air quality-climate interactions in IPCC AR6
    LIAO Hong GAO Yucheng CHEN Donglin DAI Huibin DU Nan FANG Li KANG Ling QIAN Jing QIN Zhuofan WANG Ye XIE Peifu YANG Hao ZHANG Danyuting
    2021, 44(5):658-666. DOI: 10.13878/j.cnki.dqkxxb.20210823011
    [Abstract](1089) [HTML](2211) [PDF 25.96 M](2168)
    This article introduces the new advances in air quality-climate interactions in the Sixth Assessment Report (AR6) of the Intergovernmental Panel on Climate Change (IPCC).AR6 presented emission-based estimates of the effective radiative forcing (ERF) of major air pollutants or their precursors, which have important implications for understanding the climatic effects of air pollution control measures.AR6 quantified the changes in global mean surface air temperature (GSAT) by anthropogenic emissions.Over 1750-2019, anthropogenic ERF was estimated to lead to change in GSAT by 1.29 (0.99-1.65)℃, in which changes in well-mixed greenhouse gases, O3, and aerosols contributed 1.58 (1.17-2.17)℃、0.23 (0.11-0.39)℃、-0.50 (-0.22——0.96)℃, respectively.Changes in emissions of SO2 since 1750 have made a dominant contribution to the effective radiation forcing (ERF) of aerosols through aerosol-cloud interactions (high confidence), which partially offset the warming caused by anthropogenic emissions of greenhouse gases (high confidence).AR6 assessed for the first time the sensitivity of surface ozone concentration to temperature, which is -0.2——2 nL·L-1·℃-1 in remote areas and 0.2-2 nL·L-1·℃-1 in polluted regions.With respect to the impact of climate change on PM2.5, model results show low consistency about wheather climate change increases or decreases PM2.5.
    11  Advances in scientific understanding on compound extreme events
    YU Rong ZHAI Panmao
    2021, 44(5):645-649. DOI: 10.13878/j.cnki.dqkxxb.20210824006
    [Abstract](1033) [HTML](2771) [PDF 803.80 K](2125)
    In recent years, extreme weather and climate events have occurred frequently, and are often compound extreme events formed by the interweaving of a variety of events.They have attracted extensive attention and research due to their serious hazards.In order to better understand compound extreme events, IPCC AR6 evaluated the latest research results of compound extreme events based on existing new evidence, and obtained some new understandings.The definition of compound extreme events is expanded.Focusing on heatwave and drought compound extreme events, compound floods and wildfires, the variation characteristics of compound extreme events are evaluated, the dependence among multiple factors of compound extreme events is discussed, the attribution analysis of the impact of human activities is carried out, and the possible projection in the future is given.These assessment results have enriched the current basic understanding of compound extreme events.However, according to the existing assessment, it can be seen that there are still insufficient understandings of the mechanism of occurrence and development of compound extreme events.At the same time, it is still necessary to further improve cross-disciplinary, cross-departmental and cross-regional research, strengthen the assessment of formation mechanism and projection of compound extreme events and their impact and risk on ecosystem, economy and society, and improve the adaptability to regional climate change in the future.
    12  A brief interpretation of drought change from IPCC Sixth Assessment Report
    JIANG Dabang WANG Xiaoxin
    2021, 44(5):650-653. DOI: 10.13878/j.cnki.dqkxxb.20210810007
    [Abstract](726) [HTML](838) [PDF 1.85 M](1793)
    In August 2021, the Intergovernmental Panel on Climate Change (IPCC) released the Summary for Policymakers of the Physical Science Basis in the Sixth Assessment Report (AR6), which mainly made a systematic assessment of the scientific research progress of climate change since the Fifth Assessment Report (AR5) in 2013, and used the new generation climate model to project future climate change under the new shared socio-economic path scenario.Based on the materials of relevant chapters in AR5 and AR6, this paper interpreted the assessment conclusion of drought change.
    13  Impact of humanactivities on climate system:an interpretation of Chapter Ⅲ of WGⅠreport of IPCC AR6
    SUN Ying
    2021, 44(5):654-657. DOI: 10.13878/j.cnki.dqkxxb.20210816009
    [Abstract](932) [HTML](4495) [PDF 782.64 K](1691)
    In August 2021, the Working Group Ⅰ(WGI) report of the Sixth Assessment Report (AR6) of the Intergovernmental Panel on Climate Change (IPCC) was released.The report has concluded that human activities have warmed the atmosphere, ocean and land.Widespread and rapid changes in the atmosphere, ocean, cryosphere and biospherehave occurred.This paper presents the main conclusions of the report on the impact of human activities on the climate system, including the impact of human activities on the atmosphere and surface, the cryosphere, the ocean, the biosphere and the climate variability.It is clear that based on recent literatures in the filed of climate change detection and attribution, anthropogenic forcing signal, which is dominated by greenhouse gases, has been detected in multivariable changes in the climate system.The uses of the newest observational data, the latest generation of climate models and the updated attribution methods provide solid basis for these conclusions.
    14  Global warming:scientific progress from AR5 to AR6
    ZHOU Botao
    2021, 44(5):667-671. DOI: 10.13878/j.cnki.dqkxxb.20210815009
    [Abstract](584) [HTML](1118) [PDF 798.72 K](1533)
    Since the release of the Fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change (IPCC), the international scientific community has made a number of significant progresses in the field of climate system change, which deepen our understanding on climate change.These scientific progresses and findings have been assessed objectively and comprehensively in the Working Group I (WGI) report of the Sixth Assessment Report (AR6)of IPCC.Given that temperature is the most direct indicator of global climate change, this paper briefly reviews the scientific cognition of the observed changes, attribution and projection from AR5 to AR6 from the perspective of changes in surface temperature.Compared to AR5, AR6 further confirms the objective fact of global warming since 1850 with stronger evidence, and the signals of human influenceon global warming are much clearer.The future amplitude of global warming depends on the efforts of greenhouse gas emission reduction.

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