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Abstract This paper compares recent global energy scenarios developed by governments, international bodies, businesses and the scientific community. We divide the scenarios into three broad classes: outlooks which extrapolate current trends and anticipate policy developments; exploratory scenarios which may consider disruptions; and normative scenarios which derive energy system pathways consistent with a long-term goal. Many organisations are starting to blend outlooks, exploratory and normative approaches. The paper covers trends in primary energy demand to 2040, snapshots of the energy mix in 2040, drivers of demand, and the evolution of scenarios projections developed in recent years. We find sharp divergences between outlooks and normative scenarios compatible with the Paris Agreement on climate change. All published outlooks imply that the world is not on an energy pathway compatible with the Paris Agreement. We conclude with an assessment of emerging themes including: scenario benchmarking and group think; adaptation of scenarios to real world developments; and the plausibility of different types of scenarios. We propose that more dialogue between scenario developers from the scientific community and those working in governments and commercial organisations could be beneficial. Research focusing on the organisational processes through which scenarios are developed could usefully extend this work.

AbstractGlobal 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.

AbstractIntegrated assessment models (IAMs) connect trends in future socioeconomic and technological development with impacts on the environment, such as global climate change. They occupy a critical position at the global science‐policy interface. IAMs and associated scenarios have come under intense scrutiny, with critiques addressing both methodological and substantive issues, such as land use, carbon dioxide removal and technology performance. Criticisms have also addressed the transparency of IAM methods and assumptions as well as the transparency of the Intergovernmental Panel on Climate Change (IPCC) assessment of IAMs. This paper, authored by the co‐chairs of IPCC Working Group III and members of the Technical Support Unit, documents activities aiming to enhance the transparency of IAMs and their assessment. It includes a history of IPCC's approach to scenarios covering the formation of the Integrated Assessment Modeling Consortium (IAMC) in 2007 and the emergence of the approach by which IPCC facilitates the development of scenarios, but does not produce them itself. An IPCC Expert Meeting at the start of the current assessment cycle made transparency recommendations targeted at both the research community and IPCC. The community has taken steps to “open the black box” by moving toward open‐source and web‐publishing IAM documentation. IPCC has included an Annex to its next report focusing on scenarios and modeling methodologies. An open call for scenario data linked to the current IPCC report includes an expanded set of input and output variables. This paper ends with suggested criteria for measuring the success of these efforts to improve transparency.This article is categorized under: Integrated Assessment of Climate Change > Applications of Integrated Assessment to Climate Change Integrated Assessment of Climate Change > Integrated Assessment Modeling