Focus on Evidence Synthesis for Climate Solutions

The adoption of healthy diets with low environmental impact has been widely promoted as an important climate change mitigation strategy. Typically, these diets are high in plant-sourced and low in animal-sourced and processed foods. Despite the fact that their environmental impacts vary, they are often referred to as 'sustainable diets'. Here we systematically review the available published evidence on the effect of 'sustainable diets' on environmental footprints and human health. Eight databases (OvidSP-Medline, OvidSP-Embase, EBSCO-GreenFILE, Web of Science Core Collection, Scopus, OvidSP-CAB-Abstracts, OvidSP-AGRIS, and OvidSP-Global Health) were searched to identify literature (published 1999–2019) reporting health effects and environmental footprints of 'sustainable diets'. Available evidence was mapped and pooled analysis was conducted by unique combinations of diet pattern, health and environmental outcome. Eighteen studies (412 measurements) met our inclusion criteria, distinguishing twelve non-mutually exclusive sustainable diet patterns, six environmental outcomes, and seven health outcomes. In 87% of measurements (n = 151) positive health outcomes were reported from 'sustainable diets' (average relative health improvement: 4.09% [95% CI −0.10–8.29]) when comparing 'sustainable diets' to current/baseline consumption patterns. Greenhouse gas emissions associated with 'sustainable diets' were on average 25.8%[95%CI −27.0 to −14.6] lower than current/baseline consumption patterns, with vegan diets reporting the largest reduction in GHG-emissions (−70.3% [95% CI: −90.2 to −50.4]), however, water use was frequently reported to be higher than current/baseline diets. Multiple benefits for both health and the environment were reported in the majority (n = 315[76%]) of measurements. We identified consistent evidence of both positive health effects and reduced environmental footprints accruing from 'sustainable diets'. The notable exception of increased water use associated with 'sustainable diets' identifies that co-benefits are not universal and some trade-offs are likely. When carefully designed, evidence-based, and adapted to contextual factors, dietary change could play a pivotal role in climate change mitigation, sustainable food systems, and future population health.

Climate change emerged as an issue of science, but its broad ranging impacts and potential mitigation strategies mean it is of significance to all people across sectors, interests, and nations. As a result, the traditional fact-centred way of communicating information about climate change is not necessarily the best strategy for engaging the full breadth of publics. In communication practice and scholarship, framing is an approach that emphasises certain attributes of an issue over others and as a consequence shapes how that issue is understood. This has led to the scholarly exploration of framing as a technique for tailoring climate change communication to engage diverse publics. Over the past two decades, research has examined a range of different frames for the communication of climate change, such as Public health, National security and Economic prosperity/development. With this literature now rapidly expanding, it is crucial to synthesise existing evidence so that future research efforts and climate communication interventions are best informed about the current knowledge-base and research gaps. This article presents this synthesis in the form of a systematic map. We systematically searched scholarly (Scopus and Web of Science) and grey literature databases for English-language climate change framing literature. All articles were screened at the title/abstract and full-text level, with included articles incorporated into a Microsoft (MS) Excel database. The information extracted from the literature included bibliometric, geographical and other data pertaining to study design and the climate change frames examined. Our systematic map includes 274 articles (281 studies). The most common frames appearing in this literature base (making up about 50% of the total) were Scientific, Economic and Environmental. Other frames such as Public health, Disaster and Morality/ethics appear to be gaining more scholarly attention in recent years. Almost half of the collected studies are from the United States but there is a growing trend of studies comparing climate change frames from other countries. Climate change frames are numerous and can have different efficacies depending upon country and social-political context. Research needs to be reflexive in its approach to understand the broader impact of framing in climate change communication and should continue to employ multi-national studies and explore climate change framing effects in under-researched nations to combat bias.

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.

Energy is crucial to household health and consumption needs, and for enabling productive uses that enhance development. Yet increasing energy use also affects climate change. While 'off-grid' renewable solutions offer the possibility of climate-sensitive development, some argue that a low emissions energy pathway conflicts with economic development. This systematic review analyzes the state of knowledge concerning the surprisingly understudied nexus of climate and development implications of electrification projects in low- and middle-income countries, focusing on whether and how these two potentially conflicting objectives can be balanced. After systematically identifying and coding the relevant literature, we describe the relationships between generation technologies, energy services, emissions, and development outcomes therein. Despite the increasing importance of this topic, relevant literature is scant, and largely supports the idea that the development impacts from off-grid, low-emissions renewables have been muted in the past, relative to high-emissions grid-based electrification. Our results hint at the fact that more sustainable long term development will inevitably require supporting poor countries in their efforts to develop high-quality electricity grids that are more reliant on low carbon technologies.

With climate change impacts being felt across Europe, governments have started to invest in designing and implementing adaptation actions. The means through which governments adapt is generally referred to as policy instruments. Although there is a large body of adaptation policy literature emerging, our comprehensive understanding of policy instruments is limited nor do we know much about how scholarship on adaptation is addressing critical questions about policy instrument choice and effectiveness to support policy practice. In this article we map academic scholarship on climate change adaptation policy instruments in Europe. Using systematic approaches, we identify 184 relevant articles published 2014–2019. Our findings show that research is heavily concentrated on a limited number of western-European countries, with hardly any insights from eastern Europe and smaller countries. Most studies do not connect climate change impacts and risks with policy instruments, making assessment of policy effectiveness difficult, if not impossible. We argue that expanding the geographical scope of future research and enhancing the diversity of study types across Europe is critical for advancing theories on climate change adaptation policy, as well as providing useful recommendations for policy makers to strengthen the solution space and accelerate climate change adaptation.

African cities are largely less-built with agile informal settlements and multiple ecologies that harbor different pathways for resilience to climate change. We undertook a qualitative systematic review of academic and policy evidence, to address the question of what interventions are emerging at neigbourhood to city scale to enhance resilience to climate change in Africa. Resilience at neigbourhood scale often stems from harnessing the local resource base and technologies for urban agriculture and forestry; alternative energy from wastes; grassed drainages for protection against erosion; recreation along dry riverbeds; fog-water harvesting; and adjustments in irrigation schedules. At city scale, planning is targeted at buildings, mobility and energy service delivery as the objects to be made resilient. The review established that evidence on comparisons across regions is mainly on East, West and South African cities, and much less on cities in Northern and Central Africa. Ecological comparisons are majorly on coastal and inland cities, with minimal representation of semi-arid and mountainous cities. Resilience efforts in capital cities are the most dominant in the literature, with less emphasis on secondary cities and towns, which is necessary for a deeper understanding of the role played by inter-municipal and inter-metropolitan collaborations. African cities can bring context-sensitivity to global debates on climate resilience, if theoretical perspectives are generated from emerging interventions across case studies. We conclude with suggestions on what future research needs to take on, if evidence on resilience to climate change in African cities is to be strengthened.

Background: Environmental changes are predicted to threaten human health, agricultural production and food security. Whilst their impact has been evaluated for major cereals, legumes and vegetables, no systematic evidence synthesis has been performed to date evaluating impact of environmental change on fruits, nuts and seeds (FN&S)—valuable sources of nutrients and pivotal in reducing risks of non-communicable disease. Methods: We systematically searched seven databases, identifying available published literature (1970–2018) evaluating impacts of water availability and salinity, temperature, carbon dioxide (CO₂) and ozone (O₃) on yields and nutritional quality of FN&S. Dose-response relationships were assessed and, where possible, mean yield changes relative to baseline conditions were calculated. Results: 81 papers on fruits and 24 papers on nuts and seeds were identified, detailing 582 and 167 experiments respectively. A 50% reduction in water availability and a 3–4dS m⁻¹ increase in water salinity resulted in significant fruit yield reductions (mean yield changes: −20.7% [95%CI −43.1% to −1.7%]; and −28.2% [95%CI −53.0% to −3.4%] respectively). A 75%–100% increase in CO₂ concentrations resulted in positive yield impacts (+37.8%; [95%CI 4.1% to 71.5%]; and 10.1%; [95%CI −30.0% to 50.3%] for fruits and nuts respectively). Evidence on yield impacts of increased O₃ concentrations and elevated temperatures (>25 °C) was scarce, but consistently negative. The positive effect of elevated CO₂ levels appeared to attenuate with simultaneous exposure to elevated temperatures. Data on impacts of environmental change on nutritional quality of FN&S were sparse, with mixed results. Discussion: In the absence of adaptation strategies, predicted environmental changes will reduce yields of FN&S. With global intake already well-below WHO recommendations, declining FN&S yields may adversely affect population health. Adaptation strategies and careful agricultural and food system planning will be essential to optimise crop productivity in the context of future environmental changes, thereby supporting and safeguarding sustainable and resilient food systems.

Tipping points have become a key concept in research on climate change, indicating points of abrupt transition in biophysical systems as well as transformative changes in adaptation and mitigation strategies. However, the potential existence of tipping points in socio-economic systems has remained underexplored, whereas they might be highly policy relevant. This paper describes characteristics of climate change induced socio-economic tipping points (SETPs) to guide future research on SETPS to inform climate policy. We review existing literature to create a tipping point typology and to derive the following SETP definition: a climate change induced, abrupt change of a socio-economic system, into a new, fundamentally different state. Through stakeholder consultation, we identify 22 candidate SETP examples with policy relevance for Europe. Three of these are described in higher detail to identify their tipping point characteristics (stable states, mechanisms and abrupt change): the collapse of winter sports tourism, farmland abandonment and sea-level rise-induced migration. We find that stakeholder perceptions play an important role in describing SETPs. The role of climate drivers is difficult to isolate from other drivers because of complex interplays with socio-economic factors. In some cases, the rate of change rather than the magnitude of change causes a tipping point. The clearest SETPs are found on small system scales. On a national to continental scale, SETPs are less obvious because they are difficult to separate from their associated economic substitution effects and policy response. Some proposed adaptation measures are so transformative that their implementations can be considered an SETP in terms of 'response to climate change'. Future research can focus on identification and impact analysis of tipping points using stylized models, on the exceedance of stakeholder-defined critical thresholds in the RCP/SSP space and on the macro-economic impacts of new system states.

In the context of strong evidence on mounting climate-related risks and impacts across the globe, the need for 'transformational change' in climate risk management and adaptation responses has been brought forward as an important element to achieve the Paris ambitions. In the past decade, the concept has experienced increasing popularity in policy debates and academic discussions but has seen heterogeneous applications and little practical insight. The paper aims to identify relevant perspectives on transformative approaches and transformational change in the context of climate risk management and adaptation to propose an actionable definition for practical application. Using a systematic search and review approach, we review different perspectives across policy and scientific publications, focusing on work published in the past decade and identify common features of what transformational change in the context of climate risk management and adaptation may involve. We show that different perspectives on transformational change in the context of climate risk management and adaptation persist, but certain areas of convergence are discernible. This includes understanding transformational change as part of a spectrum that begins with incremental change; involves climate risk management and adaptation measures focusing on deep-rooted, system-level change and tends to aim at enabling more just and sustainable futures; often oriented towards the long-term, in anticipation of future climate-related developments. In addition, we identify an 'operationalisation gap' in terms of translating transformational change ambitions into concrete transformative measures that can be replicated in practice.

Global greenhouse gas (GHG) emissions can be traced to five economic sectors: energy, industry, buildings, transport and AFOLU (agriculture, forestry and other land uses). In this topical review, we synthesise the literature to explain recent trends in global and regional emissions in each of these sectors. To contextualise our review, we present estimates of GHG emissions trends by sector from 1990 to 2018, describing the major sources of emissions growth, stability and decline across ten global regions. Overall, the literature and data emphasise that progress towards reducing GHG emissions has been limited. The prominent global pattern is a continuation of underlying drivers with few signs of emerging limits to demand, nor of a deep shift towards the delivery of low and zero carbon services across sectors. We observe a moderate decarbonisation of energy systems in Europe and North America, driven by fuel switching and the increasing penetration of renewables. By contrast, in rapidly industrialising regions, fossil-based energy systems have continuously expanded, only very recently slowing down in their growth. Strong demand for materials, floor area, energy services and travel have driven emissions growth in the industry, buildings and transport sectors, particularly in Eastern Asia, Southern Asia and South-East Asia. An expansion of agriculture into carbon-dense tropical forest areas has driven recent increases in AFOLU emissions in Latin America, South-East Asia and Africa. Identifying, understanding, and tackling the most persistent and climate-damaging trends across sectors is a fundamental concern for research and policy as humanity treads deeper into the Anthropocene.

The scientific literature on climate change adaptation has become too large to assess manually. Beyond standard scientometrics, questions about if and how the field is progressing thus remain largely unanswered. Here we provide a novel, inquisitive, computer-assisted evidence mapping methodology that combines expert interviews (n = 26) and structural topic modelling to evaluate open-ended research questions on progress in the field. We apply this to 62 191 adaptation-relevant scientific publications (1988–2020), selected through supervised machine learning from a comprehensive climate change query. Comparing the literature to key benchmarks of mature adaptation research, our findings align with trends in the adaptation literature observed by most experts: the field is maturing, growing rapidly, and diversifying, with social science and implementation topics arising next to the still-dominant natural sciences and impacts-focused research. Formally assessing the representativeness of IPCC citations, we find evidence of a delay effect for fast-growing areas of research like adaptation strategies and governance. Similarly, we show significant topic biases by geographic location: especially disaster and development-related topics are often studied in Southern countries by authors from the North, while Northern countries dominate governance topics. Moreover, there is a general paucity of research in some highly vulnerable countries. Experts lastly signal a need for meaningful stakeholder involvement. Expanding on the methods presented here would aid the comprehensive and transparent monitoring of adaptation research. For the evidence synthesis community, our methodology provides an example of how to move beyond the descriptive towards the inquisitive and formally evaluating research questions.

We undertake a systematic review of peer-reviewed literature to arrive at recommendations for shaping communications about uncertainty in scientific climate-related findings. Climate communications often report on scientific findings that contain different sources of uncertainty. Potential users of these communications are members of the general public, as well as decision makers and climate advisors from government, business and non-governmental institutions worldwide. Many of these users may lack formal training in climate science or related disciplines. We systematically review the English-language peer-reviewed empirical literature from cognitive and behavioral sciences and related fields, which examines how users perceive communications about uncertainty in scientific climate-related findings. We aim to summarize how users' responses to communications about uncertainty in scientific climate-related findings are associated with characteristics of the decision context, including climate change consequences and types of uncertainty as well as user characteristics, such as climate change beliefs, environmental worldviews, political ideology, numerical skills, and others. We also aimed to identify what general recommendations for communications about uncertainty in scientific climate-related findings can be delineated. We find that studies of communications about uncertainty in scientific climate-related findings substantially varied in how they operationalized uncertainty, as well as how they measured responses. Studies mostly focused on uncertainty stemming from conflicting information, such as diverging model estimates or experts, or from expressions of imprecision such as ranges. Among other things, users' understanding was improved when climate communications about uncertainty in scientific climate-related findings were presented with explanations about why climate information was uncertain, and when ranges were presented with lower and upper numerical bounds. Users' understanding also improved if they expressed stronger beliefs about climate change, or had better numerical skills. Based on these findings, we provide emerging recommendations on how to best present communications about uncertainty in scientific climate-related findings; and we identify research gaps.

Background. Climate change and climate variability interact with political, economic, social, demographic, and other environmental drivers to change the scale and patterns of human migration⁵. In the context of accelerating climate change and breaches to other planetary boundaries, there is an urgent need to better understand how migrant health can be protected and promoted in the context of a changing climate to manage safe and orderly migration⁶. While research has focused on the separate dyads of (i) climate change and migration and (ii) climate change and health, limited consideration has been given to the nexus between climate change, migration, and health. This assessment synthesizes research that has investigated this relationship since 1990. Methods. Following an a priori protocol and with the assistance of a subject librarian, systematic searches were conducted in four academic databases (PubMed, Scopus, Ovid Medline, and Global Health) and Google Scholar for empirical studies investigating migration and health in the context of climate change with any study design between 1990 and 2018. The search results underwent a two-stage screening process and the eligible studies were subjected to quality appraisal using a mixed methods appraisal tool. Data extraction and a meta-synthesis followed producing outputs deemed most useful for policy, practice, and further research. Findings. The registered protocol and search strategy revealed 1904 studies of which 180 were screened in full- text and 50 were included in the meta-synthesis. Overall, the methodological and reporting quality of the included studies was high. This assessment produced five main findings: (1) there is a paucity of empirical research investigating the climate-health-migration nexus; (2) the relationships between migration and health in the context of climate change are strongly heterogeneous and global findings are unlikely to emerge; (3) studies have examined diverse health issues associated with migration in the context of climate change including changing patterns of infectious disease, non-communicable disease, psychosocial conditions, and access to health care; (4) food and water security are important mediators between climate change, human mobility and health outcomes; (5) there is no consistent approach to integrating climate data in studies exploring migration and health in the context of climate change. Conclusions. Although migrant health and climate-related health risks are significant population health concerns, there has been limited consideration of the complex connections between climate change, migration, and health. This assessment indicates that there are potentially important intersections between climate-health- migration and that further research is required to better understand this nexus. To date and based on this assessment, it seems important that research and policy related to migration also consider the links between climate change and health and that migration is considered a determinant of health in climate change and health research. Given the diverse mobility patterns that arise in the context of climate change, responsive approaches are required that address the vulnerabilities of communities at risk of, or involved in forced migration, whilst supporting the adaptive potential of mobility responses. There is a need to develop policies that are responsive enough to protect health and health determinants especially food and water security regardless of the climate scenario. The degree to which climate data are meaningfully integrated into research exploring migration and health in the context of a changing climate warrants further consideration and analysis, to maintain quality in this emerging field of nexus research. Health systems that are migrant inclusive and climate-resilient have the potential to mitigate the worst health impacts of climate-related migration.

Over time African cities and their residents have responded to climate impacts in increasingly creative ways, based on local knowledge and available resources. Overviews of adaptation policy, plans and actions have largely been lacking for Africa, particularly at the local, city level. We applied a systematic map to assess what the human responses to climate impacts are in African cities, noting the climate drivers of these actions, the range of responses, where they have taken place, and who the actors are. Standardized, pre-selected search terms were used to systematically search peer-reviewed and grey literature, using Web of Science, Scopus, and Google. Publications were screened based on pre-approved inclusion criteria, and actions described in included articles were coded using categories from key conceptual framing papers on climate change adaptation. Of 2 042 peer-reviewed and 60 grey-literature publications, 252 underwent full-text screening, with 121 included for coding. We recorded 1 504 actions, taking place in 41 cities from 21 African countries, in response to various climate drivers. Anticipatory and reactive actions were taken by actors, from individuals to international agencies, and we highlighted successful adaptations, those taking advantage of climate impacts, and maladaptive actions. Combinations of climatic and non-climatic stimuli induced adaptive responses, which were frequently based on local knowledge, and provided a base upon which government action could build. Residents of informal settlements had less adaptive capacity than those in formal settlements, and government action could build their resilience. Since development is affected by climate impacts, climate change information should be integrated into development programmes.

The Paris Agreement (PA) sets out to strengthen the global response to climate change, setting targets for mitigation, adaptation, and finance, and establishing mechanisms through which to achieve these targets. The effectiveness of the PA's mechanisms in achieving its targets, however, has been questioned. This review systematically maps the peer-reviewed literature on the PA, categorizing the available evidence on whether or not the 'Paris Regime' can be effective. We split our analysis into three methodologically distinct sections: first we categorize the literature according to the mechanisms being studied. We find a diverse body of literature, albeit with a clear focus on mitigation, and identify adaptation and capacity building to be clear gaps. Second, we carry out a content analysis, identifying common drivers of, barriers to, and recommendations for effectiveness. Here we find mixed evidence, with potential drivers often qualified by more concrete barriers. Thirdly, we use scientometrics to identify six research clusters. These cover loss and damage, finance, legal issues, international politics, experimental evidence, and studies on tracking progress on the PA's targets. We conclude with a narrative discussion of our findings, presenting three central themes. First, transparency is widely considered a precondition for the PA to be institutionally effective. However, a lack of clear reporting standards and comparable information renders the PA's transparency provisions ineffective. Second, environmental effectiveness relies on national ambition, of which there is currently too little. It remains unclear to which extent the Paris Regime structure itself can induce significant ratcheting-up of ambition. Finally, the PA facilitates the diffusion of norms, enables learning and the sharing of best practices. This production of shared norms provides the most promising avenue for overcoming the current lack of ambition. One of the primary successes of the PA is in providing a platform for the exchange of experiences and ideas.

Many countries committed to climate action by adopting the Paris Agreement and Sustainable Development Goals in 2015. This study synthesizes 40 years of scientific evidence of what may be an important benefit of these commitments: the non-use value of biodiversity conservation. The synthesis investigates whether biodiversity values can be integrated into climate change damage estimates based on non-use valuation studies of different threats to biodiversity. In the absence of estimates of public willingness to pay (WTP) to avoid the adverse impacts of anthropogenic climate change on biodiversity, we synthesize non-use values for biodiversity conservation from stated preference studies that account for a heterogeneous set of biodiversity threats. We test whether biodiversity non-use values are affected by the threats that policies aim to address, be it human activities or other threats. We estimate meta-regression models in which we explain the variation in these non-use values by accounting for the observed heterogeneity in good, methodology, sample, and context characteristics. We estimate meta-regression models using 159 observations from 62 publications. The models suggest that non-use values for biodiversity conservation addressing human impacts may be larger than those addressing other threats. We also find that non-use values are generally not sensitive to which biodiversity indicators, habitat types, or taxonomic groups are valued. We predict that the mean annual WTP for avoiding human-caused biodiversity losses ranges from 0.2 to 0.4% of GDP per capita. Our findings suggest that state-of-the-art climate change damage functions in integrated assessment models may underestimate actual damage costs because they do not incorporate the premium that the public is willing to pay to avoid human-caused biodiversity losses.

We develop an evidence map of the academic research on energy transitions (ETs) with a focus on what that literature says about public policy for addressing climate change. In this article, the questions we ask are: What trends do we see in the topics that occur in journal articles on the energy transition? And to what extent has public policy been a focus? Where do we need or see energy transitions happening? Our approach involves: (1) using two literature databases to identify 4875 relevant ET articles over the period 1970–2018; (2) identifying important topics within ET using topic modeling via latent Dirichlet allocation on the abstracts of the articles; and (3) conducting a robustness check on the topics and analysis on the policy-relevant topics. This study contributes to the ETs research by providing the first systematic overview of peer-reviewed articles on ETs. We find that the number of academic articles covering ETs has increased by nearly a factor of 50 since 2008, 67% of them are policy related. Research on governance is pervasive in the literature and contains multiple topics differentiated by substantive foci. Some topics on the social-technical, social-behavioral, and political aspects of transition governance are becoming increasingly popular. Network analysis shows transition governance, energy economics and climate implications, and energy technologies comprise the three largest clusters of topics, but we observe a lack of connectedness between governance topics and technology topics. In the policy-relevant literature, we see a growing number of articles on technological and institutional innovation, and examples from leader countries, especially in Europe. We find only a quarter of articles discussed ETs in developing countries, which is not aligned with a recurring theme, their importance to the global ET.

It is critical to ensure climate and energy policies are just, equitable and beneficial for communities, both to sustain public support for decarbonisation and address multifaceted societal challenges. Our objective in this article is to examine the diverse social outcomes that have resulted from climate policies, in varying contexts worldwide, over the past few decades. We review 203 ex-post climate policy assessments that analyse social outcomes in the literature. We systematically and comprehensively map out this work, identifying articles on carbon, energy and transport taxes, feed-in-tariffs, subsidies, direct procurement policies, large renewable deployment projects, and other regulatory and market-based interventions. We code each article in terms of their studied social outcomes and effects, with a focus on electricity access, energy affordability, community cohesion, employment, distributional and equity issues, livelihoods and poverty, procedural justice, subjective well-being and drudgery. Our analysis finds that climate and energy policies often fall short of delivering positive social outcomes. Nonetheless, across country contexts and policy types there are manifold examples of climate policymaking that does deliver on both social and climate goals. This requires attending to distributive and procedural justice in policy design, and making use of appropriate mechanisms to ensure that policy costs and benefits are fairly shared. We emphasize the need to further advance ex-post policy assessments and learn about what policies work for a just transition.

We conduct a systematic and interdisciplinary review of empirical literature assessing evidence on induced innovation in energy and related technologies. We explore links between demand-drivers (both market-wide and targeted); indicators of innovation (principally, patents); and outcomes (cost reduction, efficiency, and multi-sector/macro consequences). We build on existing reviews in different fields and assess over 200 papers containing original data analysis. Papers linking drivers to patents, and indicators of cumulative capacity to cost reductions (experience curves), dominate the literature. The former does not directly link patents to outcomes; the latter does not directly test for the causal impact of on cost reductions. Diverse other literatures provide additional evidence concerning the links between deployment, innovation activities, and outcomes. We derive three main conclusions. (a) Demand-pull forces enhance patenting; econometric studies find positive impacts in industry, electricity and transport sectors in all but a few specific cases. This applies to all drivers—general energy prices, carbon prices, and targeted interventions that build markets. (b) Technology costs decline with cumulative investment for almost every technology studied across all time periods, when controlled for other factors. Numerous lines of evidence point to dominant causality from at-scale deployment (prior to self-sustaining diffusion) to cost reduction in this relationship. (c) Overall innovation is cumulative, multi-faceted, and self-reinforcing in its direction (path-dependent). We conclude with brief observations on implications for modelling and policy. In interpreting these results, we suggest distinguishing the economics of active deployment, from more passive diffusion processes, and draw the following implications. There is a role for policy diversity and experimentation, with evaluation of potential gains from innovation in the broadest sense. Consequently, endogenising innovation in large-scale models is important for deriving policy-relevant conclusions. Finally, seeking to relate quantitative economic evaluation to the qualitative socio-technical transitions literatures could be a fruitful area for future research.

Climate change adaptation responses are being developed and delivered in many parts of the world in the absence of detailed knowledge of their effects on public health. Here we present the results of a systematic review of peer-reviewed literature reporting the effects on health of climate change adaptation responses in low- and middle-income countries (LMICs). The review used the 'Global Adaptation Mapping Initiative' database (comprising 1682 publications related to climate change adaptation responses) that was constructed through systematic literature searches in Scopus, Web of Science and Google Scholar (2013–2020). For this study, further screening was performed to identify studies from LMICs reporting the effects on human health of climate change adaptation responses. Studies were categorised by study design and data were extracted on geographic region, population under investigation, type of adaptation response and reported health effects. The review identified 99 studies (1117 reported outcomes), reporting evidence from 66 LMICs. Only two studies were ex ante formal evaluations of climate change adaptation responses. Papers reported adaptation responses related to flooding, rainfall, drought and extreme heat, predominantly through behaviour change, and infrastructural and technological improvements. Reported (direct and intermediate) health outcomes included reduction in infectious disease incidence, improved access to water/sanitation and improved food security. All-cause mortality was rarely reported, and no papers were identified reporting on maternal and child health. Reported maladaptations were predominantly related to widening of inequalities and unforeseen co-harms. Reporting and publication-bias seems likely with only 3.5% of all 1117 health outcomes reported to be negative. Our review identified some evidence that climate change adaptation responses may have benefits for human health but the overall paucity of evidence is concerning and represents a major missed opportunity for learning. There is an urgent need for greater focus on the funding, design, evaluation and standardised reporting of the effects on health of climate change adaptation responses to enable evidence-based policy action.

A rapid coal phase-out is needed to meet the goals of the Paris Agreement, but is hindered by serious challenges ranging from vested interests to the risks of social disruption. To understand how to organize a global coal phase-out, it is crucial to go beyond cost-effective climate mitigation scenarios and learn from the experience of previous coal transitions. Despite the relevance of the topic, evidence remains fragmented throughout different research fields, and not easily accessible. To address this gap, this paper provides a systematic map and comprehensive review of the literature on historical coal transitions. We use computer-assisted systematic mapping and review methods to chart and evaluate the available evidence on historical declines in coal production and consumption. We extracted a dataset of 278 case studies from 194 publications, covering coal transitions in 44 countries and ranging from the end of the 19th century until 2021. We find a relatively recent and rapidly expanding body of literature reflecting the growing importance of an early coal phase-out in scientific and political debates. Previous evidence has primarily focused on the United Kingdom, the United States, and Germany, while other countries that experienced large coal declines, like those in Eastern Europe, are strongly underrepresented. An increasing number of studies, mostly published in the last 5 years, has been focusing on China. Most of the countries successfully reducing coal dependency have undergone both demand-side and supply-side transitions. This supports the use of policy approaches targeting both demand and supply to achieve a complete coal phase-out. From a political economy perspective, our dataset highlights that most transitions are driven by rising production costs for coal, falling prices for alternative energies, or local environmental concerns, especially regarding air pollution. The main challenges for coal-dependent regions are structural change transformations, in particular for industry and labor. Rising unemployment is the most largely documented outcome in the sample. Policymakers at multiple levels are instrumental in facilitating coal transitions. They rely mainly on regulatory instruments to foster the transitions and compensation schemes or investment plans to deal with their transformative processes. Even though many models suggest that coal phase-outs are among the low-hanging fruits on the way to climate neutrality and meeting the international climate goals, our case studies analysis highlights the intricate political economy at work that needs to be addressed through well-designed and just policies.

Long-lived capital-stocks (LLCS) such as infrastructure and buildings have significant and long-lasting implications for greenhouse gas emissions. They contribute to carbon lock-in and may hinder a rapid decarbonization of energy systems. Here we provide a systematic map of the literature on carbon lock-in induced by LLCS. Based on a structured search of the Web of Science and Scopus, we identified 226 publications from 38 095 search results using a supervised machine learning approach. We show biases toward power generation and toward developed countries. We also identify 11 indicators used to quantify carbon lock-in. Quantifications of committed emissions (cumulative emissions that would occur over the remaining operational lifetime of an asset) or stranded assets (premature retirement/retrofitting or under-utilization of assets along a given pathway) are the most commonly used metrics, whereas institutional indicators are scarcely represented. The synthesis of quantifications shows that (i) global committed emissions have slightly increased over time, (ii) coal power plants are a major source of committed emissions and are exposed to risk of becoming stranded, (iii) delayed mitigation action increases stranded assets and (iv) sectoral distribution and amount of stranded assets differ between countries. A thematic analysis of policy implications highlights the need to assure stability and legitimacy of climate policies and to enable coordination between stakeholders. Carbon pricing is one of the most cited policy instrument, but the literature emphasizes that it should not be the only instrument used and should instead be complemented with other policy instruments, such as technical regulations and financial support for low carbon capital deployment. Further research is warranted on urban-scale, in developing countries and outside the electricity generation sector, notably on buildings, where stranded assets could be high.

A rapid phase-out of unabated coal use is essential to limit global warming to below 2 °C. This review presents a comprehensive assessment of coal transitions in mitigation scenarios consistent with the Paris Agreement, using data from more than 1500 publicly available scenarios generated by more than 30 integrated assessment models. Our ensemble analysis uses clustering techniques to categorize coal transition pathways in models and bridges evidence on technological learning and innovation with historical data of energy systems. Six key findings emerge: First, we identify three archetypal coal transitions within Paris-consistent mitigation pathways. About 38% of scenarios are 'coal phase out' trajectories and rapidly reduce coal consumption to near zero. 'Coal persistence' pathways (42%) reduce coal consumption much more gradually and incompletely. The remaining 20% follow 'coal resurgence' pathways, characterized by increased coal consumption in the second half of the century. Second, coal persistence and resurgence archetypes rely on the widespread availability and rapid scale-up of carbon capture and storage technology (CCS). Third, coal-transition archetypes spread across all levels of climate policy ambition and scenario cycles, reflecting their dependence on model structures and assumptions. Fourth, most baseline scenarios—including the shared socio-economic pathways (SSPs)—show much higher coal dependency compared to historical observations over the last 60 years. Fifth, coal-transition scenarios consistently incorporate very optimistic assumptions about the cost and scalability of CCS technologies, while being pessimistic about the cost and scalability of renewable energy technologies. Sixth, evaluation against coal-dependent baseline scenarios suggests that many mitigation scenarios overestimate the technical difficulty and costs of coal phase-outs. To improve future research, we recommend using up-to-date cost data and evidence about innovation and diffusion dynamics of different groups of zero or low-carbon technologies. Revised SSP quantifications need to incorporate projected technology learning and consistent cost structures, while reflecting recent trends in coal consumption.

Adaptation is a central component of climate policy, helping manage and reduce risks. Sometimes, however, adaptation to climate change may consume energy, threatening efforts to reduce greenhouse gas emissions. Examples are numerous, and include the use of air conditioning or water desalination. Nevertheless, no clear view exists on how energy demand globally can be impacted by climate change. In this paper we systematically map existing evidence on how and to what extent adaptation responses to climate change may impact energy demand. The literature is large, fast-growing and spans several disciplines, but we identify several research gaps. First, the literature focuses almost exclusively on heating and cooling demand, while overlooking other potential sectors. It also focuses heavily on a few world regions, while local specific climate and socio-economic conditions may highly influence the impacts, and focuses largely on average demand, while often disregarding peak energy demand. Finally, and most importantly, only a handful of papers—most of them with a specific geographical scope—consider that different adaptation possibilities may lead to different impacts on energy demand, which is an important prerequisite if the impact of adaptation on energy demand is to be lowered and maladaptation to be avoided. The reviewed papers study for the most part similar options, and most adaptation possibilities are conversely studied by just one or two papers.