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The Intergovernmental Panel on Climate Change (IPCC) has been renewing its communications activities in the current assessment cycle, building on the innovations that underpinned the Fifth Assessment Report. An Expert Meeting on Communication in Oslo in 2016 sought to compile and discuss the lessons learnt during Fifth Assessment Report and inform the Communications Strategies for the Sixth Assessment Report (The overall Communications Strategy is adopted by the IPCC. Individual communications strategies for the various reports are signed off by the Chair and respective Co-Chairs.) This article describes the progress made, in the context of the IPCC’s communications goals and specific challenges. Developments in the current cycle include a more systematic approach to developing key statements to communicate the findings of the reports. The IPCC has expanded the number and geographic range of its outreach activities, targeting interested stakeholders beyond the core audience of policymakers. Communications work was strengthened by reinforcing the Working Group Technical Support Units, which support the author teams, with communications specialists. The first product in this cycle, the 2018 Special Report on Global Warming of 1.5 °C, was by some measures the most influential report on climate change to date. It attracted enormous media coverage, transforming and galvanizing public interest in global warming. With the two subsequent special reports in 2019 on land and the ocean and cryosphere, this has focused attention and scrutiny on the IPCC. The latest report, Climate Change 2021: The Physical Science Basis, was released in August 2021 and broke all records for coverage of an IPCC report. This makes effective communication all the more important, for the remainder of the current cycle due for completion in 2022 and beyond.

In August 2019, the Intergovernmental Panel on Climate Change (IPCC) published its Special Report on Climate Change and Land (SRCCL), which generated extensive societal debate and interest in mainstream and social media. Using computational and conceptual text analysis, we examined more than 6,000 English-language posts on Twitter to establish the relative presence of different topics. Then, we assessed their levels of toxicity and sentiment polarity as an indication of contention and controversy. We find first that meat consumption and dietary options became one of the most discussed issues on Twitter in response to the IPCC report, even though it was a relatively minor element of the report; second, this new issue of controversy (meat and diet) had similar, high levels of toxicity to strongly contentious issues in previous IPCC reports (skepticism about climate science and the credibility of the IPCC). We suggest that this is in part a reflection of increasingly polarized narratives about meat and diet found in other areas of public discussion and of a movement away from criticism of climate science towards criticism of climate solutions. Finally, we discuss the possible implications of these findings for the work of the IPCC in anticipating responses to its reports and responding to them effectively.

Climate change is an indisputable threat to human health, especially for societies already confronted with rising social inequality, political and economic uncertainty, and a cascade of concurrent environmental challenges. Archaeological data about past climate and environment provide an important source of evidence about the potential challenges humans face and the long-term outcomes of alternative short-term adaptive strategies. Evidence from well-dated archaeological human skeletons and mummified remains speaks directly to patterns of human health over time through changing circumstances. Here, we describe variation in human epidemiological patterns in the context of past rapid climate change (RCC) events and other periods of past environmental change. Case studies confirm that human communities responded to environmental changes in diverse ways depending on historical, sociocultural, and biological contingencies. Certain factors, such as social inequality and disproportionate access to resources in large, complex societies may influence the probability of major sociopolitical disruptions and reorganizations—commonly known as “collapse.” This survey of Holocene human–environmental relations demonstrates how flexibility, variation, and maintenance of Indigenous knowledge can be mitigating factors in the face of environmental challenges. Although contemporary climate change is more rapid and of greater magnitude than the RCC events and other environmental changes we discuss here, these lessons from the past provide clarity about potential priorities for equitable, sustainable development and the constraints of modernity we must address.

Policy relevance is the raison d’être for the Intergovernmental Panel on Climate Change (IPCC), yet few studies have analysed what the concept entails, not least from the perspective of key target groups for the IPCC. We present a framework which enables analysis of how different actor strategies (heating up and cooling down) contribute to shape relevance-making in specific political situations when IPCC knowledge is interpreted and used. Drawing on empirical evidence from the reception and use of the Special Report on Global Warming of 1.5°C (SR15) across three policy making levels, the paper demonstrates different examples of creating policy relevance. First, the paper analyses the origin of SR15 and the failed attempts to formally acknowledge SR15 in the United Nations Framework Convention on Climate Change (UNFCCC) process. Second, it investigates how SR15 has been used to develop and legitimize the EU net-zero target and the European Green Deal. Third, the paper demonstrates how SR15 has been used both for legitimizing and challenging climate policy at the national level, using the example of Norway. In sum, the reception of SR15 demonstrates that while IPCC outputs have resulted in controversy at the international level, they have been highly relevant at regional and national levels. The analysis shows that policy relevance is context-dependent and indirect—created through processes involving many actors, institutions, and types of knowledge. Situating these findings within the larger shift in the international climate regime implied by the Paris Agreement, the paper concludes with a set of empirically grounded recommendations for how the IPCC may approach the goal of policy relevance post-Paris.

The Working Group III (WGIII) contribution to the 2022 IPCC Report (AR6) provides an updated global assessment of the climate change mitigation process in terms of developments in emission reduction and mitigation efforts, and an assessment of the impact of national climate pledges in relation to long-term emissions goals. New additions are chapters on the social aspects of mitigation and on innovation, technology development and transfer. One of the key messages of the Report is that accelerated and equitable climate action in climate change mitigation and adaptation is critical to sustainable development, with synergies and trade-offs between the SDGs and mitigation and adaptation options highlighted, making connections with the AR6 WGII report. A well-resourced just transition is core to shifting South Africa's development pathway to increased sustainability, and fostering climate-resilience and low GHG emissions.

Paleontology has provided invaluable basic knowledge on the history of life on Earth. The discipline can also provide substantial knowledge to societal challenges such as climate change. The long-term perspective of climate change impacts on natural systems is both a unique selling point and a major obstacle to becoming more pertinent for policy-relevant bodies like the Intergovernmental Panel on Climate Change (IPCC). Repeated experiments on the impacts of climate change without anthropogenic disturbance facilitate the extraction of climate triggers in biodiversity changes. At the same time, the long timescales over which paleontological changes are usually assessed are beyond the scope of policymakers. Based on firsthand experience with the IPCC and a quantitative analysis of its cited literature, we argue that the differences in temporal scope are less of an issue than inappropriate framing and reporting of most paleontological publications. Accepting that some obstacles will remain, paleontology can quickly improve its relevance by targeting climate change impacts more directly and focusing on effect sizes and relevance for projections, particularly on higher-end climate change scenarios.

There is emerging evidence of the important role of indigenous knowledge for climate change adaptation. The necessity to consider different knowledge systems in climate change research has been established in the fifth assessment report (AR5) of the Intergovernmental Panel on Climate Change (IPCC). However, gaps in author expertise and inconsistent assessment by the IPCC lead to a regionally heterogeneous and thematically generic coverage of the topic. We conducted a scoping review of peer-reviewed academic literature to support better integration of the existing and emerging research on indigenous knowledge in IPCC assessments. The research question underpinning this scoping review is: How is evidence of indigenous knowledge on climate change adaptation geographically and thematically distributed in the peer-reviewed academic literature? As the first systematic global evidence map of indigenous knowledge in the climate adaptation literature, the study provides an overview of the evidence of indigenous knowledge for adaptation across regions and categorises relevant concepts related to indigenous knowledge and their contexts in the climate change literature across disciplines. The results show knowledge clusters around tropical rural areas, subtropics, drylands, and adaptation through planning and practice and behavioural measures. Knowledge gaps include research in northern and central Africa, northern Asia, South America, Australia, urban areas, and adaptation through capacity building, as well as institutional and psychological adaptation. This review supports the assessment of indigenous knowledge in the IPCC AR6 and also provides a basis for follow-up research, e.g. bibliometric analysis, primary research of underrepresented regions, and review of grey literature.

Inhabitants of low-lying islands face increased threats due to climate change as a result of their higher exposure and lesser adaptive capacity. Sagar Island, the largest inhabited estuarine island of Sundarbans, is experiencing severe coastal erosion, frequent cyclones, flooding, storm surges, and breaching of embankments, resulting in land, livelihood, and property loss, and the displacement of people at a huge scale. The present study assessed climate change-induced vulnerability and risk for Sagar Island, India, using an integrated geostatistical and geoinformatics-based approach. Based on the IPCC AR5 framework, the proportion of variance of 26 exposure, hazard, sensitivity, and adaptive capacity parameters was measured and analyzed. The results showed that 19.5% of mouzas (administrative units of the island), with 15.33% of the population at the southern part of the island, i.e., Sibpur–Dhablat, Bankimnagar–Sumatinagar, and Beguakhali–Mahismari, are at high risk (0.70–0.80). It has been concluded that the island has undergone tremendous land system transformations and changes in climatic patterns. Therefore, there is a need to formulate comprehensive adaptation strategies at the policy- and decision-making levels to help the communities of this island deal with the adverse impacts of climate change. The findings of this study will help adaptation strategies based on site-specific information and sustainable management for the marginalized populations living in similar islands worldwide.

Knowledge of the atmospheric chemistry of reactive greenhouse gases is needed to accurately quantify the relationship between human activities and climate, and to incorporate uncertainty in our projections of greenhouse gas abundances. We present a method for estimating the fraction of greenhouse gases attributable to human activities, both currently and for future scenarios. Key variables used to calculate the atmospheric chemistry and budgets of major non‐CO2greenhouse gases are codified along with their uncertainties, and then used to project budgets and abundances under the new climate‐change scenarios. This new approach uses our knowledge of changing abundances and lifetimes to estimate current total anthropogenic emissions, independently and possibly more accurately than inventory‐based scenarios. We derive a present‐day atmospheric lifetime for methane (CH4) of 9.1 ± 0.9 y and anthropogenic emissions of 352 ± 45 Tg/y (64% of total emissions). For N2O, corresponding values are 131 ± 10 y and 6.5 ± 1.3 TgN/y (41% of total); and for HFC‐134a, the lifetime is 14.2 ± 1.5 y. Key Points A new method proposed for projecting non‐CO2 GHG with uncertainty Enables the community to evaluate the importance of different processes Independent evaluation of natural and anthropogenic GHG emissions