Climate and climate change sciences: 30 years of IPCC assessment reports Valérie Masson-Delmotte @valmasdel
Emissions from fossil fuel use and industry Global emissions from fossil fuel and industry: 36.2 ± 2 GtCO 2 in 2016, 62% over 1990 Projection for 2017: 36.8 ± 2 GtCO 2, 2.0% higher than 2016 Uncertainty is ±5% for one standard deviation (IPCC likely range) Estimates for 2015 and 2016 are preliminary. Growth rate is adjusted for the leap year in 2016. Source: CDIAC; Le Quéré et al 2017; Global Carbon Budget 2017
Warming due to human influence Haustein et al, Scientific Report, 2017
More warming = more risks Global warming ( C) above 1850-1900 2017 Unique and threatened systems Extreme events Distribution of impacts Global aggregated impacts Large scale singular events O Neil et al, NCC, 2017
Paris Agreement mechanism Long term target Emission decrease towards carbon neutrality Talanoa Dialogue 2018 Global stocktake 2023 adaptation, mitigation, finance Rogelj et al, Nature, 2016
A major scientific endeavour Fluid physics Thermodynamics Radiative transfers Chronology, proxies Super computors Satellites Antiquity Middle Age 17 th C Weather instruments 19 th C Networks Ice ages Greenhouse effect 20 th C Past climate Climate modelling
From knowledge production 20000 Number of peer-review papers with the keyword «climate change» 15000 10000 5000 0 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015
to the assessment of the state of knowledge The IPCC assesses the scientific, technical and socio-economic information relevant to understanding the scientific basis of risk of human-induced climate change, its potential impacts and options for adaptation and mitigation. The IPCC is organized in Working Groups and one Task Force : - WGI : the physical science basis - WGII : impacts, adaptation and vulnerability - WGIII : mitigation of climate change - Task Force on national greenhouse gas inventories IPCC reports must be policy-relevant but not policy-prescriptive COMPREHENSIVE, OBJECTIVE, OPEN AND TRANSPARENT BASIS
Science/Policy Interface IPCC jointly established by WMO and UNEP, action endorsed by the UN General Assembly Intergovernmental Panel: 195 member States appointing National Focal Points Hundreds of scientists and experts from around the world are involved in the preparation of IPCC reports Plenary Bureaux Working Group (WG) I The Physical Science Basis WGII Impacts, Adaptation & Vulnerability WGIII Mitigation of Climate Change Task Force on National Greenhouse Gas Inventories Expert Reviewers Authors Review Editors
From published literature to Summaries for Policy-Makers Assessments are based on published literature, preferably peerreviewed; updates of figures/tables using published methodology are OK, but new research is not. Assessment statements must be traceable and the lines of evidence made clear. Executive Summaries distill key results/messages from each chapter, and Summary for Policy Makers (SPM) distills even further. SPM must be approved line-by-line by governments. Underlying chapter text provides foundation for SPM.
How does an assessment differ from a review? It is intended to objectively summarize the state of (scientific) knowledge in a balanced way, including an assessment of confidence/uncertainty. It is to be policy relevant (and not policy prescriptive); therefore it need not comprehensively cover all of the literature in the field. Indicative bullet points provide guidance It is a consensus document produced by the author team, not a collection of individual contributions. Assessment statements should be agreed as a group, based on expert judgment. Calibrated language is an essential element.
Using a calibrated language to report confidence in findings
Concrete example : Chapter section and summary statement {this section is 14 pages long}
Concrete example Chapter Executive Summary
Concrete example : Summary for Policy Makers
FAR SAR TAR AR4 AR5 AR6 IPCC jointly established by WMO and UNEP UNFCCC Kyoto Adaptation 2 C limit Paris Agreement Protocol UNFCCC Global Stocktake Nobel Peace Prize 1988 1995 2007 2018 2023 1970s-1980s 1990 2001 2013-2014
1990 broad overview of climate change science, discussion of uncertainties and evidence of warming 1995 The balance of evidence suggests a discernible human influence on global climate 2001 new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities 2007 "Warming of the climate system is unequivocal " 2013 Human influence on the climate system is clear. Improvements:
Methods of attribution : global scale IPCC AR5 New developments for single extreme events Example : role of high sea surface temperature on wind speeds of Hurricane Sandy Magnusson et al 2013 WMR
Emergence of sea level science - 1950s 1960s 1970s 1980s 1990s Astronomical theory and ice ages Vulnerability of West Antarctic ice sheet 2000s 2010s Extreme sea level Interior rivers Glacier mass balance Observed sea Coastal habitats level rise Irreversibility Fast glacier flow Regional aspects Sea level projections Ice sheet - ocean
Sea level in the FAR (1990) and AR5 (2013) Over the last century, global sea level has increased by 10-20 cm Over the period 1901 to 2010, global mean sea level rose by 0.19 [0.17 to 0.21] m. 1.7 [1.5 to 1.9] mm yr 1 between 1901 and 2010 2.0 [1.7 to 2.3] mm yr 1 between 1971 and 2010, 3.2 [2.8 to 3.6] mm yr 1 between 1993 and 2010. Over the period 1993 to 2010, global mean sea level rise is, with high confidence, consistent with the sum of the observed contributions from ocean thermal expansion due to warming, from changes in glaciers, Greenland ice sheet, Antarctic ice sheet and land water storage. It is very likely that there is a substantial anthropogenic contribution to the global mean sea level rise since the 1970s.
Sea level in the FAR (1990) and AR5 (2013) Under the business as usual scenario, the predicted rise is about 65cm by the end of the next century. There will be significant regional variations. For RCP8.5, the rise by the year 2100 will likely be in the range of 0.52 to 0.98 (relative to 1986-2005) There is currently insufficient evidence to evaluate the probability of specific levels above the assessed likely range. Sea level rise will not be uniform. By the end of the 21st century, it is very likely that sea level will rise in more than about 95% of the ocean area. About 70% of the coastlines worldwide are projected to experience sea level change within 20% of the global mean sea level change.
Sea level in the FAR (1990) and AR5 (2013) Although, over the next 100 years, the effect of the Antarctic and Greenland ice sheets is expected to be small they make a major contribution to the uncertainty in predictions Changes in outflow from both ice sheets combined will likely make a contribution in the range of 0.03 to 0.20 m by 2081 2100 Only the collapse of marine-based sectors of the Antarctic ice sheet, if initiated, could cause global mean sea level to rise substantially above the likely range during the 21st century. However, there is medium confidence that this additional contribution would not exceed several tenths of a meter of sea level rise during the 21st century.
Sea level in the FAR (1990) and AR5 (2013) Even if greenhouse forcing increased no further, there would still be a commitment to a continuing sea level rise for many decades and even centuries due to delays in climate ocean and ice mass responses It is virtually certain that global mean sea level rise will continue beyond 2100, with sea level rise due to thermal expansion to continue for many centuries. RCP 2.6 : <1 m by 2300 RCP8.5 : 1 m to more than 3 m Sustained mass loss by ice sheets would cause larger sea level rise, and some part of the mass loss might be irreversible. There is high confidence that sustained warming greater than some threshold would lead to the near-complete loss of the m Greenland ice sheet over a millennium or more, causing a global mean sea level rise of up to 7 m.
Sea level in the FAR (1990) and AR5 (2013) The most severe effects of sea level rise are likely to result from extreme events (for example, storm surges) the incidence of which may be affected by climatic change It is very likely that there will be a significant increase in the occurrence of future sea level extremes by 2050 and 2100. This increase will primarily be the result of an increase in mean sea level (high confidence), with the frequency of a particular sea level extreme increasing by an order of magnitude or more in some regions by the end of the 21st century. There is low confidence in region-specific projections of storminess and associated storm surges.
The Fifth Assessment Report (AR5) 830 Coordinating Lead Authors, Lead Authors and Review Editors from 85 countries Developed Countries Developing Countries & Economies in Transition Male writing team members Female writing team members New to the IPCC process Previously involved 36% 64% 21% 79% 37% 63%
Specificities of the IPCC AR6 2030 international agenda Paris Agreement Knowledge: risk management & solutions
Aspirations for the AR6 More experts from developing countries More integration across Working Groups High level scenarios and concrete steps Connections with sustainable development goals Focus on solutions linked to domestic challenges Poverty alleviation, job creation, health, innovation, energy access Strengthen relevance for a variety of stakeholders Three Conventions (climate, biodiversity, desertification) Subnational policy makers (cities ) Business, industry, finance Improve communication (graphics, SPM, FAQ )
IPCC report preparation steps Cut-off dates for cited references
May 2019 Emission inventories Schedule Oct. 2018 Oct. 2019 Global warming of 1.5 o C Oceans and cryosphere April 2021 October 2021 April 2022 The Physical Science Basis Climate Change Impacts, Adaptation and Vulnerability The Synthesis Report Facilitative dialogue UNFCCC Land Mitigation of Climate Change Global stocktake 2023 UNFCCC Aug. 2019 July 2021 March2018 May 2018 May 2018 Cities and Climate Change Science Conference Expert Meeting on Assessing Climate Information for Regions Expert Meeting on Short Lived Climate Forcers
Global warming of 1.5 C (SR1.5) Chapter 1: Framing and context Chapter 2: Mitigation pathways compatible with 1.5 C in the context of sustainable development 15 40 Chapter 3: Impacts of 1.5 C global warming on natural and human systems 60 Chapter 4: Strengthening and implementing the global response to the threat of climate change Chapter 5: Sustainable development, poverty eradication and reducing inequalities 50 20
IPCC Special Report on Climate Change and Land (SRCCL) Chapter 1: Framing and context Chapter 2: Land-climate interactions Chapter 3: Desertification Chapter 4: Land degradation Chapter 5: Food security Chapter 6 : Interlinkages between desertification, land degradation, food security, and greenhouse gas fluxes : synergies, trade-offs and integrated response options Chapter 7 : Risk management and decision making In relation to sustainable development 15 50 35-40 40 50 40 40
IPCC Special Report on the Ocean and Cryosphere in a Changing Climate (SROCC) Chapter 1: Framing and context Chapter 2: High mountain areas Chapter 3: Polar regions Chapter 4: Sea level rise and implications for low lying islands, coasts and communities Chapter 5: Changing ocean, marine ecosystems, and dependent communities Chapter 6 : Extremes, abrupt changes and managing risks Box : Low lying islands and coasts 15 30 50 50 65 20 <5
WGI Outline Summary for Policy Makers Technical Summary Large-scale climate change Chapter 1: Framing, context, methods Chapter 2: Changing state of the climate system Chapter 3: Human influence on the climate system Chapter 4: Future global climate: scenario-based projections and near-term information Chapter 5: Global carbon and other biogeochemical cycles and feedbacks Chapter 6: Short-lived climate forcers Chapter 7: The Earth s energy budget, climate feedbacks, and climate sensitivity Chapter 8: Water cycle changes Chapter 9: Ocean, cryosphere, and sea level change Chapter 10: Linking global to regional climate change Chapter 11: Weather and climate extreme events in a changing climate Chapter 12: Climate change information for regional impact and for risk assessment Annexes incl. options for a Regional Atlas and Technical Annexes Glossary Index
WGI Outline Summary for Policy Makers Technical Summary Chapter 1: Framing, context, methods Chapter 2: Changing state of the climate system Climate processes Chapter 3: Human influence on the climate system Chapter 4: Future global climate: scenario-based projections and near-term information Chapter 5: Global carbon and other biogeochemical cycles and feedbacks Chapter 6: Short-lived climate forcers Chapter 7: The Earth s energy budget, climate feedbacks, and climate sensitivity Chapter 8: Water cycle changes Chapter 9: Ocean, cryosphere, and sea level change Chapter 10: Linking global to regional climate change Chapter 11: Weather and climate extreme events in a changing climate Chapter 12: Climate change information for regional impact and for risk assessment Annexes incl. options for a Regional Atlas and Technical Annexes Glossary Index
WGI Outline Summary for Policy Makers Technical Summary Chapter 1: Framing, context, methods Chapter 2: Changing state of the climate system Chapter 3: Human influence on the climate system Regional climate information Chapter 4: Future global climate: scenario-based projections and near-term information Chapter 5: Global carbon and other biogeochemical cycles and feedbacks Chapter 6: Short-lived climate forcers Chapter 7: The Earth s energy budget, climate feedbacks, and climate sensitivity Chapter 8: Water cycle changes Chapter 9: Ocean, cryosphere, and sea level change Chapter 10: Linking global to regional climate change Chapter 11: Weather and climate extreme events in a changing climate Chapter 12: Climate change information for regional impact and for risk assessment Annexes incl. options for a Regional Atlas and Technical Annexes Glossary Index
WGI Outline Summary for Policy Makers Technical Summary Link to WGIII Chapter 1: Framing, context, methods Chapter 2: Changing state of the climate system Chapter 3: Human influence on the climate system Chapter 4: Future global climate: scenario-based projections and near-term information Chapter 5: Global carbon and other biogeochemical cycles and feedbacks Chapter 6: Short-lived climate forcers Chapter 7: The Earth s energy budget, climate feedbacks, and climate sensitivity Chapter 8: Water cycle changes Chapter 9: Ocean, cryosphere, and sea level change Chapter 10: Linking global to regional climate change Chapter 11: Weather and climate extreme events in a changing climate Chapter 12: Climate change information for regional impact and risk for assessment Annexes incl. options for a Regional Atlas and Technical Annexes Glossary Index Link to WGII
Chapter 1: Point of departure and key concepts WGII Chapters SECTION 1: Risks, adaptation and sustainability for systems impacted by climate change Chapter 2: Terrestrial and freshwater ecosystems and their services Chapter 3: Ocean and coastal ecosystems and their services Chapter 4: Water Chapter 5: Food, fibre, and other ecosystem products Chapter 6: Cities, settlements and key infrastructure Chapter 7: Health, wellbeing and the changing structure of communities Chapter 8: Poverty, livelihoods and sustainable development SECTION 2: Regions Chapter 9: Africa Chapter 10: Asia Chapter 11: Australasia Chapter 12: Central and South America Chapter 13: Europe Chapter 14: North America Chapter 15: Small Islands CROSS-CHAPTER PAPERS Biodiversity hotspots (land, coasts and oceans) Cities and settlements by the sea Deserts, semi-arid areas, and desertification Mediterranean region Mountains Polar regions Tropical forests SECTION 3: Sustainable development pathways: integrating adaptation and mitigation Chapter 16: Key risks across sectors and regions Chapter 17: Decision-making options for managing risk Chapter 18: Climate resilient development pathways* *connection to WG III ANNEX I: Regional Atlas
1. Introduction and framing Outline of WG III AR6 on mitigation Framing (1 chapter) High-level assessment of emission trends, drivers and pathways (3 chapters) 2. Emissions trends and drivers 3. Mitigation pathways compatible with long-term goals 4. Mitigation and development pathways in the near- to mid-term Sectoral chapters (8 chapters) 5: Demand, services and social aspects of mitigation 6: Energy systems 9. Buildings 7. Agriculture, Forestry, and Other Land Uses 10. Transport 8. Urban systems and other settlements 11. Industry 12. Cross sectoral perspectives Institutional drivers (2 chapters) 13. National and sub-national policies and institutions 14. International cooperation Set up sustainable development as key framing concept Balancing sources and sinks/warming levels NDCs, emissions peaking, midcentury long-term low greenhouse gas emission development strategies Orients sectors to human needs The sectoral core: maps on to inventories Responses not captured by sectoral framing Institutions, policies and cooperation Financial and technological drivers (2 chapters) 15. Investment and finance 16. Innovation, technology development and transfer Synthesis (1 chapter) 17. Accelerating the transition in the context of sustainable development Financial flows + technological innovation Synthesis sustainable development in different geographical scales
May 2019 Emission inventories Schedule Oct. 2018 Oct. 2019 Global warming of 1.5 o C Oceans and cryosphere April 2021 October 2021 April 2022 The Physical Science Basis Climate Change Impacts, Adaptation and Vulnerability The Synthesis Report Facilitative dialogue UNFCCC Land Mitigation of Climate Change Global stocktake 2023 UNFCCC Aug. 2019 July 2021 March 2018 May 2018 May 2018 Cities and Climate Change Science Conference Expert Meeting on Assessing Climate Information for Regions Expert Meeting on Short Lived Climate Forcers
Cut-off dates for reports Report Cut-off dates for submitted papers to be cited in Second Order Drafts SR1.5 01 November 2017 15 May 2018 SROCC October 2018 May 2019 SRCCL September 2018 April 2019 Cut-off dates for papers accepted for publication to be cited in report AR6, WG1 31 January 2020 15 October 2020
Author teams Coordinating Lead Authors (CLAs) Lead Authors (LAs) Review Editors (REs) Contributing Authors (CA) Chapter Scientists (CS)
Next review processes 2017 2018 2019 SR15 FOD July SOD Approval Jan Oct SRCCL FOD May SOD Oct Approval Aug SROCC FOD Apr SOD Nov Approval Sept Outreach Activities
Closing remarks Multiple roles of IPCC reports : - assessment of the state of knowledge for governments - synthesis of available research, regional results into global context - identification of knowledge gaps and uncertainties - maturation of science and stimulation of research - teaching New knowledge is vital for IPCC assessments The review process is crucial for the quality of the assessment AR6 : a new IPCC approach with 3 special reports Which approach for the AR7 and beyond?
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Chapter 1: Framing, context, methods Executive Summary Synthesis of key findings from AR5 and earlier assessment reports, and connections to AR6 Special Reports Framing of the physical science information relevant for mitigation, adaptation, and risk assessment in the context of the Global Stocktake Assessment approach Observational and reanalysis developments since the AR5 Model and experimental design developments since the AR5 Emissions and forcing scenarios Treatment and evaluation of uncertainty throughout the report Frequently Asked Questions
Chapter 2: Changing state of the climate system Executive Summary Multi-millennial context, pre-industrial to present day Natural and anthropogenic forcings Radiative forcing Large-scale indicators of observed change in the atmosphere, ocean, cryosphere, land, and biosphere Modes of variability Frequently Asked Questions
Chapter 3: Human influence on the climate system Executive Summary Overview of model performance and development since the AR5 Simulated large-scale indicators of change in the atmosphere, ocean, cryosphere, land, and biosphere Simulated modes of variability Natural variability versus anthropogenically-forced change Attribution of large-scale observed changes Frequently Asked Questions
Chapter 4: Future global climate: scenario-based projections and near-term information Executive Summary Projections of global mean surface temperature and other key global indicators Evaluation of multi-model ensemble methods Large scale patterns of climate change Committed climate response, climate targets, overshoot, irreversibility, abrupt change Climate response to greenhouse gas removal scenarios Climate response to solar radiation management scenarios Interplay between internal variability and response to forcings, including short-lived forcers Variability and unexpected changes of global mean surface temperature Near-term predictability, sources and capabilities Synthesis of climate information in the near-term Frequently Asked Questions
Chapter 5: Global carbon and other biogeochemical cycles and feedbacks Executive Summary Feedbacks between climate and biogeochemical cycles, including paleoclimate information Ocean acidification Historical trends and variability of CO 2, CH 4 and N 2 O; sources and sinks Projections of global biogeochemical cycles from near-term to long-term Abrupt change, irreversibility Model evaluation, emergent constraints Transient climate response to cumulative emissions and remaining carbon budgets for climate targets Biogeochemical implications of land and coastal management mitigation options including greenhouse gas removal Biogeochemical implications of solar radiation management scenarios Frequently Asked Questions
Chapter 6: Short-lived climate forcers Executive Summary Key global emissions: global overview, natural, anthropogenic, historical and scenarios Observed and reconstructed concentrations and radiative forcing Direct and indirect-aerosol forcing Implications for greenhouse gas lifetimes Implications of different socio-economic and emission pathways, including urbanisation, for radiative forcing Connections to air quality and atmospheric composition Frequently Asked Questions
Chapter 7: The Earth s energy budget, climate feedbacks, and climate sensitivity Executive Summary Energy budget and its changes through time Radiative forcing: definitions, estimates, and its representation in models Climate feedbacks Sensitivity of the climate system: methods and uncertainty Empirical constraints on the sensitivity of the climate system, including paleoclimate Global warming potential, global temperature change potential, and other metrics Frequently Asked Questions
Chapter 8: Water cycle changes Executive Summary Observations, models, methods and their reliability Past, present and projected changes, trends, variability and feedbacks in the physical components of the water cycle Circulation, processes and phenomena (e.g. monsoon systems) affecting moisture and precipitation patterns, including extremes Cloud-aerosol processes affecting the water cycle Changes in seasonality of natural storage and water availability Abrupt change Confidence in projections Frequently Asked Questions
Chapter 9: Ocean, cryosphere, and sea level change Executive Summary Past and future changes in ocean circulation and properties (trends, variability and extremes) Past and future changes in marine and terrestrial cryosphere Evaluation of models and projection methods Detection and attribution Past global and regional sea level changes Projections of global and regional sea level change Abrupt change and long-term commitment Extreme water levels (tides, surge and ocean waves) Frequently Asked Questions
Chapter 10: Linking global to regional climate change Executive Summary Regional phenomena, drivers, feedbacks and teleconnections Regional scale observations and reanalyses Interplay between internal variability and forced change at the regional scale, including attribution Evaluation of model improvements, methods, including downscaling and bias adjustment and regional specificities Confidence in regional climate information, including quantification of uncertainties Scale specific methodologies e.g. urban, mountains, coastal, catchments, small islands Approaches to synthesizing information from multiple lines of evidence Frequently Asked Questions
Chapter 11: Weather and climate extreme events in a changing climate Executive Summary Extreme types encompassing weather and climate timescales and compound events (including droughts, tropical cyclones) Observations for extremes and their limitations, including paleo Mechanisms, drivers and feedbacks leading to extremes Ability of models to simulate extremes and related processes Attribution of changes in extremes and extreme events Assessment of projected changes of extremes and potential surprises Case studies across timescales Frequently Asked Questions
Chapter 12: Climate change information for regional impact and for risk assessment Executive Summary Framing: physical climate system and hazards Region-specific integration of information, including confidence Information (quantitative and qualitative) on changing hazards: present day, near term and long term Region-specific methodologies Relationship between changing hazards, global mean temperature change, scenarios and emissions Frequently Asked Questions
Ultimately what we do about climate issues depends upon the state of our scientific knowledge. Only to the extent that we have understanding can we help our governments. Governments wish to know where to focus effort and resources. The international resources that can be made available to deal with climatic problems are limited. This is so not merely because finances are limited, but because the number of scientists capable of working effectively on these problems is limited. Because of this, efforts must be focused on those climatic problems where there is an urgent need for answers, and where the state of our scientific knowledge leads us to believe that it may be possible for science to make a useful contribution. Robert White, Keynote address, World Climate Conference, 1979