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Last edited 05 Apr 2022
Intergovernmental Panel on Climate Change IPCC
The Intergovernmental Panel on Climate Change (IPCC) was established by the United Nations Environment Programme (UNEP) and the World Meteorological Organisation (WMO) in 1988 to provide a scientific assessment of climate change and its potential impacts.
The IPCC does not carry out research itself, but reviews and assesses existing research and other information. Thousands of scientists contribute voluntarily to the work of the IPCC in order that it can reflect a wide range of views and expertise. 195 countries are members of the IPCC, participating in the review process and the plenary sessions.
Its main activity is to provide regular Assessment Reports (AR) on the state of knowledge about climate change. It has produced reports in 1990, 1995, 2001, 2007, 2013 & 2014. Most recently, the sixth assessment report (AR6), described as the sixth assessment cycle, is being published in stages between 2020 and 2022. The IPCC has also produced various special reports, methodology reports, technical papers and supporting material published a regular intervals.
- The Working Group I contribution to the Sixth Assessment Report is entitled Climate Change 2021: The Physical Science Basis and was released on 9 August 2021.
- The Working Group II contribution to the Sixth Assessment Report is entitled Climate Change 2022: Impacts, Adaptation and Vulnerability and was released on 28 February 2022.
- The Working Group III contribution to the Sixth Assessment Report is entitled Climate Change 2022: Mitigation of Climate Change and was released on 4 April 2022.
- The Synthesis Report will be the last of the AR6 products will be considered in Copenhagen, Denmark, on 27-31 October.
To avoid interpretation, the Designing Buildings links above draw key text directly from the 'Summary for Policymakers' along with key points and sub-points. These summaries, along with the full reports for all working groups for reports between 2021 and 2022, can be accessed directly here: https://www.ipcc.ch/assessment-report/ar6/ The final Synthesis report will published towards the end of 2022.
The wording of these reports is significant and the final report was delayed exactly because governments did not approve some of the wording (https://edition.cnn.com/2022/04/04/world/un-ipcc-climate-report-mitigation-fossil-fuels/index.html) There is however a significant amount of obviously important text and references, so for ease of reading and to give readers a flavor of that text we have quoted directly only the introductory paragraph from each sub-section section of each report but excluded the numerous references and footnotes, as we reference the document itself.
 A The Current State of the Climate
Since AR5, improvements in observationally-based estimates and information from paleoclimate archives provide a comprehensive view of each component of the climate system and its changes to date. New climate model simulations, new analyses, and methods combining multiple lines of evidence lead to improved understanding of human influence on a wider range of climate variables, including weather and climate extremes. The time periods considered throughout this section depend upon the availability of observational products, paleoclimate archives and peer-reviewed studies."
 B Possible Climate Futures
A set of five new illustrative emissions scenarios is considered consistently across this Report to explore the climate response to a broader range of greenhouse gas (GHG), land-use and air pollutant futures than assessed in AR5. This set of scenarios drives climate model projections of changes in the climate system. These projections account for solar activity and background forcing from volcanoes. Results over the 21st century are provided for the near term (2021–2040), mid-term (2041–2060) and long term (2081–2100) relative to 1850–1900, unless otherwise stated.
 C Climate Information for Risk Assessment and Regional Adaptation
Physical climate information addresses how the climate system responds to the interplay between human influence, natural drivers and internal variability. Knowledge of the climate response and the range of possible outcomes, including low-likelihood, high impact outcomes, informs climate services, the assessment of climate-related risks, and adaptation planning. Physical climate information at global, regional and local scales is developed from multiple lines of evidence, including observational products, climate model outputs and tailored diagnostics.
 D Limiting Future Climate Change
Since AR5, estimates of remaining carbon budgets have been improved by a new methodology first presented in SR1.5, updated evidence, and the integration of results from multiple lines of evidence. A comprehensive range of possible future air pollution controls in scenarios is used to consistently assess the effects of various assumptions on projections of climate and air pollution. A novel development is the ability to ascertain when climate responses to emissions reductions would become discernible above natural climate variability, including internal variability and responses to natural drivers.
 A Introduction
Across all three AR6 working groups, risk provides a framework for understanding the increasingly severe, interconnected and often irreversible impacts of climate change on ecosystems, biodiversity, and human systems; differing impacts across regions, sectors and communities; and how to best reduce adverse consequences for current and future generations. In the context of climate change, risk can arise from the dynamic interactions among climate-related hazards (see Working Group I), the exposure and vulnerability8 of affected human and ecological systems. The risk that can be introduced by human responses to climate change is a new aspect considered in the risk concept. This report identifies 127 key risks.
Adaptation plays a key role in reducing exposure and vulnerability to climate change. Adaptation in ecological systems includes autonomous adjustments through ecological and evolutionary processes. In human systems, adaptation can be anticipatory or reactive, as well as incremental and/ or transformational. The latter changes the fundamental attributes of a social-ecological system in anticipation of climate change and its impacts. Adaptation is subject to hard and soft limits.
Resilience in the literature has a wide range of meanings. Adaptation is often organized around resilience as bouncing back and returning to a previous state after a disturbance. More broadly the term describes not just the ability to maintain essential function, identity and structure, but also the capacity for transformation.
Since AR5, the knowledge base on observed and projected impacts and risks generated by climate hazards, exposure and vulnerability has increased with impacts attributed to climate change and key risks identified across the report. Impacts and risks are expressed in terms of their damages, harms, economic, and non-economic losses. Risks from observed vulnerabilities and responses to climate change are highlighted. Risks are projected for the near-term (2021–2040), the mid (2041–2060) and long term (2081–2100), at different global warming levels and for pathways that overshoot 1.5°C global warming level for multiple decades27. Complex risks result from multiple climate hazards occurring concurrently, and from multiple risks interacting, compounding overall risk and resulting in risks transmitting through interconnected systems and across regions.
 C Adaptation Measures and Enabling Conditions
Adaptation, in response to current climate change, is reducing climate risks and vulnerability mostly via adjustment of existing systems. Many adaptation options exist and are used to help manage projected climate change impacts, but their implementation depends upon the capacity and effectiveness of governance and decision-making processes. These and other enabling conditions can also support climate-resilient development.
Climate-resilient development integrates adaptation measures and their enabling conditions (Section C) with mitigation to advance sustainable development for all. Climate resilient development involves questions of equity and system transitions in land, ocean and ecosystems; urban and infrastructure; energy; industry; and society and includes adaptations for human, ecosystem and planetary health. Pursuing climate resilient development focuses on both where people and ecosystems are co-located as well as the protection and maintenance of ecosystem function at the planetary scale. Pathways for advancing climate resilient development are development trajectories that successfully integrate mitigation and adaptation actions to advance sustainable development. Climate resilient development pathways may be temporarily coincident with any RCP and SSP scenario used throughout AR6, but do not follow any particular scenario in all places and over all time."
 A Introduction and framing
An evolving international landscape. The literature reflects, among other factors: developments in the UN Framework Convention on Climate Change (UNFCCC) process, including the outcomes of the Kyoto Protocol and the adoption of the Paris Agreement; the UN 2030 Agenda for Sustainable Development including the Sustainable Development Goals (SDGs) and the evolving roles of international cooperation, finance and innovation.
Increasing diversity of actors and approaches to mitigation. Recent literature highlights the growing role of non-state and sub-national actors including cities, businesses, Indigenous Peoples, citizens including local communities and youth, transnational initiatives, and public-private entities in the global effort to address climate change. Literature documents the global spread of climate policies and cost declines of existing and emerging low emission technologies, along with varied types and levels of mitigation efforts, and sustained reductions in greenhouse gas (GHG) emissions in some countries, and the impacts of, and some lessons from, the COVID-19 pandemic.
Close linkages between climate change mitigation, adaptation and development pathways. The development pathways taken by countries at all stages of economic development impact GHG emissions and hence shape mitigation challenges and opportunities, which vary across countries and regions. Literature explores how development choices and the establishment of enabling conditions for action and support influence the feasibility and the cost of limiting emissions. Literature highlights that climate change mitigation action designed and conducted in the context of sustainable development, equity, and poverty eradication, and rooted in the development aspirations of the societies within which they take place, will be more acceptable, durable and effective. This report covers mitigation from both targeted measures, and from policies and governance with other primary objectives.
New approaches in the assessment. In addition to the sectoral and systems chapters, the report includes, for the first time in a WG III report, chapters dedicated to demand for services, and social aspects of mitigation, and to innovation, technology development and transfer. The assessment of future pathways in this report covers near term (to 2030), medium term (up to 2050), and long term (to 2100) timescales, combining assessment of existing pledges and actions, with an assessment of emissions reductions, and their implications, associated with long-term temperature outcomes up to the year 2100. The assessment of modelled global pathways addresses ways of shifting development pathways towards sustainability. Strengthened collaboration between IPCC Working Groups is reflected in Cross-Working Group boxes that integrate physical science, climate risks and adaptation, and the mitigation of climate change.
Increasing diversity of analytic frameworks from multiple disciplines including social sciences. This report identifies multiple analytic frameworks to assess the drivers of, barriers to and options for, mitigation action. These include: economic efficiency including the benefits of avoided impacts; ethics and equity; interlinked technological and social transition processes; and socio-political frameworks, including institutions and governance. These help to identify risks and opportunities for action including co-benefits and just and equitable transitions at local, national and global scales.
 B Recent developments and current trends
B.1 Cumulative net CO2 emissions have risen since 1850. Average annual GHG emissions during 2010-2019 were higher than in any previous decade, but the rate of growth between 2010 and 2019 was lower than that between 2000 and 2009.
B.2 Net GHG emissions increase since 2010 across all sectors globally. Increasing share of emissions from urban areas. Emissions reductions, due to improvements are less than increases from rising global activity levels.
B.3 Regional contributions differ widely. Regional, and national per capita variations partly reflect different development stages, but vary widely at similar income levels. The 10% of households with highest per capita emissions contribute disproportionately large share of household emissions. At least 18 countries have sustained reductions for 10 years.
B.4 Unit costs of low-emission technologies has fallen. Innovation policy has enabled cost reductions and supported adoption, addressing innovation systems helping overcome the distributional, environmental and social impacts. This has lagged in developing countries due to weaker enablers. Digitalisation can enable reductions with good governance.
B.5 Consistent expansion of policies and laws addressing mitigation since AR5, leading to the avoidance of emissions and increased investment in low-GHG technologies and infrastructure. Policy coverage of emissions is uneven across sectors. Aligning financial flows towards Paris goals is slow and tracked climate finance unevenly distributed.
B.6 Global emissions in 2030 associated with nationally determined contributions (NDCs) announced prior to COP26 would make it likely warming will exceed 1.5°C during the 21st century. Limiting below 2°C would then rely on a rapid acceleration of mitigation efforts after 2030. Policies implemented by 2020 projected to result in higher than NDCs.
B.7 Projected cumulative future CO2 emissions over the lifetime of existing and currently planned fossil fuel infrastructure without additional abatement exceed the total cumulative net CO2 emissions in pathways that limit warming to 1.5°C (>50%) with no or limited overshoot. Approximately equal to total cumulative net CO2 in pathways limiting to 2°C (>67%).
 C System transformations to limit global warming
C.1 Global GHG emissions projected to peak between 2020 and at the latest before 2025 in pathways that limit warming to 1.5°C (>50%) limited overshoot and in those that limit warming to 2°C (>67%) assume immediate action. In both, rapid and deep GHG emissions reductions follow throughout 2030, 2040 and 2050. Without strengthening of post 2020 policies, GHG emissions are projected to rise beyond 2025, leading to a median global warming of 3.2 [2.2 to 3.5] °C by 2100.
C.2 Global net zero is reached by 2050 in modelled pathways limiting warming to 1.5°C (>50%) limited overshoot, and by 2070 in modelled pathways limiting warming to 2°C (>67%). Many continue to net negative CO2 emissions after net zero. These pathways also include deep reductions in other GHG emissions. The level of peak warming depends on cumulative CO2 emissions until the time of net zero CO2 and the change in non-CO2 climate forcers by the time of peaking. Deep GHG emissions reductions by 2030 and 2040, particularly reductions of methane emissions, lower peak warming, reduce the likelihood of overshooting warming limits and lead to less reliance on net negative CO2 emissions that reverse warming in the latter half of the century. Reaching and sustaining global net zero results in a gradual decline in warming.
C.3 All modelled pathways limiting to warming of 1.5°C (>50%) with limited overshoot, those that limit warming to 2°C (>67%) involve rapid, deep immediate GHG emission reductions in all sectors. Modelled mitigation strategies to achieve these reductions include transitioning from fossil fuels without CCS to very low- or zero-carbon energy sources, such as renewables or fossil fuels with CCS, demand side measures and improving efficiency, reducing non-CO2 emissions, and deploying carbon dioxide removal (CDR) methods to counterbalance residual GHG emissions.
C.4 Reducing GHG emissions across the full energy sector requires major transitions, including a substantial reduction in overall fossil fuel use, the deployment of low-emission energy sources, switching to alternative energy carriers, and energy efficiency and conservation. Continued installation of unabated fossil fuel infrastructure will ‘lock-in’ emissions.
C.5 Net-zero CO2 emissions from the industrial sector are challenging but possible. Reducing industry emissions will entail action throughout value chains to promote all mitigation options, including demand management, energy and materials efficiency, circular material flows, as well as abatement technologies and transformational changes in production processes. Industry reduction can be enabled by processes using electricity, hydrogen, fuels, and carbon management.
C.6 Urban areas can create opportunities to increase resource efficiency, significantly reducing emissions through systemic transition of infrastructure and urban form through low-emission development pathways towards net-zero emissions. Ambitious mitigation efforts for established, rapidly growing and emerging cities will encompass 1) reducing or changing energy and material consumption, 2) electrification, and 3) enhancing carbon uptake and storage in the urban environment. Cities can achieve net-zero emissions, but only if emissions are reduced within and outside of their administrative boundaries through supply chains, which will have beneficial cascading effects across other sectors.
C.7. In modelled global scenarios, existing buildings, if retrofitted, and buildings yet to be built, are projected to approach net zero GHG emissions in 2050 if policy packages, which combine ambitious sufficiency, efficiency, and renewable energy measures, are effectively implemented and barriers to decarbonisation are removed. Some policies increase the risk of lock-in buildings in carbon for decades while well-designed and effectively implemented mitigation interventions, in new buildings and existing ones if retrofitted, have significant potential to contribute to achieving SDGs in all regions while adapting buildings to future climate.
C.8 Demand-side options and low-GHG emissions technologies can reduce transport sector emissions in developed countries and limit emissions growth in developing countries. Demand-focused interventions can reduce demand for all transport services and support the shift to energy efficient modes. Electric vehicles powered by low emissions electricity offer the largest decarbonisation potential for land-based transport, on a life cycle basis. Sustainable biofuels can offer additional mitigation benefits in land-based transport in the short and medium term. Sustainable biofuels, low emissions hydrogen, and derivatives (including synthetic fuels) can support mitigation of CO2 emissions from shipping, aviation, and heavy-duty land transport but require production process improvements and cost reductions. Many mitigation strategies in transport would have various co-benefits, including air quality improvements, health benefits, equitable access to transportation services, reduced congestion, and reduced material demand.
C.9 Agriculture farming and other land use (FAOLU) mitigation options, when sustainably implemented, can deliver large-scale GHG emission reductions and enhanced removals, but cannot fully compensate for delayed action in other sectors. Sustainably sourced agricultural and forest products can be used instead of more GHG intensive products in other sectors. Barriers to implementation and trade- offs may result from the impacts of climate change, competing demands on land, conflicts with food security and livelihoods, the complexity of land ownership and management systems, and cultural aspects. There are many country-specific opportunities to provide co-benefits (such as biodiversity conservation, ecosystem services, and livelihoods) and avoid risks (for example, through adaptation to climate change).
C.10 Demand-side mitigation encompasses changes in infrastructure use, end-use technology adoption, and socio-cultural and behavioural change. Demand-side measures and new ways of end-use service provision can reduce global GHG emissions in end use sectors by 40-70% by 2050 compared to baseline scenarios, while some regions and socioeconomic groups require additional energy and resources. Demand side mitigation response options are consistent with improving basic wellbeing for all.
C.11 The deployment of carbon dioxide removal (CDR) to counterbalance hard-to-abate residual emissions is unavoidable if net zero CO2 or GHG emissions are to be achieved. The scale and timing of deployment will depend on the trajectories of gross emission reductions in different sectors. Upscaling the deployment of CDR depends on developing effective approaches to address feasibility and sustainability constraints especially at large scales.
C.12 Mitigation options costing USD100 tCO2-eq-1 or less could reduce global GHG emissions by at least half the 2019 level by 2030. Global GDP continues to grow in modelled pathways but, without accounting for the economic benefits of mitigation action from avoided damages from climate change nor from reduced adaptation costs, it is a few percent lower in 2050 compared to pathways without mitigation beyond current policies. The global economic benefit of limiting warming to 2°C is reported to exceed the cost of mitigation in most of the assessed literature.
 D Linkages between mitigation, adaptation, and sustainable development
D.1 Accelerated and equitable climate action in mitigating, and adapting to, climate change impacts is critical to sustainable development. Climate change actions can also result in trade-offs. The trade-offs of individual options could be managed through policy design. The Sustainable Development Goals (SDGs) adopted under the UN 2030 Agenda for Sustainable Development can be used as a basis for evaluating climate action in the context of sustainable development.
D.2 There is a strong link between sustainable development, vulnerability and climate risks. Limited economic, social and institutional resources often result in high vulnerability and low adaptive capacity, especially in developing countries. Several response options deliver both mitigation and adaptation outcomes, especially in human settlements, land management, and in relation to ecosystems. However, land and aquatic ecosystems can be adversely affected by some mitigation actions, depending on their implementation. Coordinated cross-sectoral policies and planning can maximise synergies and avoid or reduce trade-offs between mitigation and adaptation.
D.3 Enhanced mitigation and broader action to shift development pathways towards sustainability will have distributional consequences within and between countries. Attention to equity, broad and meaningful participation of all relevant actors in decision-making at all scales can build social trust, and deepen and widen support for transformative changes.
 E. Strengthening the response
E.1 There are mitigation options which are feasible to deploy at scale in the near term. Feasibility differs across sectors and regions, and according to capacities and the speed and scale of implementation. Barriers to feasibility would need to be reduced or removed, and enabling conditions strengthened to deploy mitigation options at scale. These barriers and enablers include geophysical, environmental-ecological, technological, and economic factors, and especially institutional and socio-cultural factors. Strengthened near-term action beyond the NDCs can reduce and/or avoid long-term feasibility challenges of global modelled pathways that limit warming to 1.5 °C (>50%) with no or limited overshoot.
E.2 In all countries, mitigation efforts embedded within the wider development context can increase the pace, depth and breadth of emissions reductions. Policies that shift development pathways towards sustainability can broaden the portfolio of available mitigation responses, and enable the pursuit of synergies with development objectives. Actions can be taken now to shift development pathways and accelerate mitigation and transitions across systems.
E.3 Climate governance, acting through laws, strategies and institutions, based on national circumstances, supports mitigation by providing frameworks through which diverse actors interact, and a basis for policy development and implementation. Climate governance is most effective when it integrates multiple policy domains, helps realise synergies minimize trade-offs, connecting national and sub-national policy-making. Effective, equitable climate governance builds on engagement with civil society, political actors, businesses, youth, labour, media, Indigenous Peoples and communities.
E.4 Regulatory and economic instruments have already been deployed successfully. Instrument design can help address equity and other objectives. These could support deep emissions reductions and stimulate innovation if scaled up and applied more widely. Policy packages that enable innovation and build capacity are better able to support a shift towards equitable low-emission futures than are individual policies. Economy-wide packages, consistent with national circumstances, can meet short-term economic goals while reducing emissions, shifting pathways towards sustainability.
E.5 Tracked financial flows fall short of the levels needed to achieve mitigation goals across all sectors and regions. The challenge of closing gaps is largest in developing countries as a whole. Scaling up mitigation financial flows can be supported by clear policy choices and signals from governments and the international community. (high confidence) Accelerated international financial cooperation is a critical enabler of low-GHG and just transitions, and can address inequities in access to finance and the costs of, and vulnerability to, the impacts of climate change
E.6 International cooperation is a critical enabler for achieving ambitious climate change mitigation goals. The UNFCCC, Kyoto Protocol, and Paris Agreement are supporting rising levels of national ambition and encouraging development and implementation of climate policies, although gaps remain. Partnerships, agreements, institutions and initiatives operating at the sub- global and sectoral levels and engaging multiple actors are emerging, with mixed levels of effectiveness.
In October 2018, the IPCC released a report warning that there are only 12 years for global warming to be kept to a maximum of 1.5ºC. Beyond this, they warn, the risks of drought, floods, extreme heat and mass poverty will be significantly worsened.
Debra Roberts, a co-chair of the working group on impacts, said; “It’s a line in the sand and what it says to our species is that this is the moment and we must act now... This is the largest clarion bell from the science community and I hope it mobilises people and dents the mood of complacency.”
In response, Julie Hirigoyen, Chief Executive at UKGBC said; "This report from the IPCC is a wake-up call for governments and businesses across the globe. The construction and property industry in the UK is an economic juggernaut, and our buildings account for approximately 30% of carbon emissions. It is also the industry with the most cost-effective means of reducing carbon emissions so it will be a vital catalyst for change in the wider economy."
Colin Goodwin, Technical Director at BSRIA, said; "As an industry, we collectively need to, not only take action on climate change and stabilize the climate to avoid its worst impacts, but get on track to meet the UK’s climate change obligations. The UK's net carbon emissions should be reduced by 60 per cent by 2030 – and to zero by 2050 or at least 80 per cent of 1990 levels by 2050."
- Climate change science.
- Chlorofluorocarbons CFCs.
- COP21 Paris 2015.
- CRC Energy Efficiency Scheme.
- Earth overshoot day.
- Energy Act.
- Energy Related Products Regulations.
- Environmental consultant.
- Environmental impact assessment.
- Environmental legislation.
- ICE launches engineering route map to deliver UN SDGs.
- Mean lean green.
- Smart cities.
- Sustainable development.
- Sustainable materials.
- The future of UK power generation.
- Zero carbon homes.
- Zero carbon non-domestic buildings.
 External references
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