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The Paris Agreement requires reaching net-zero carbon emissions, but a debate exists on how fast this can be achieved. This study establishes scenarios with different feasibility constraints and finds that the institutional dimension plays a key role for determining the feasible peak temperature.

A risk-based, spatially explicit analysis of carbon storage in sedimentary basins establishes a prudent planetary limit of around 1,460 Gt of geological carbon storage, which requires making explicit decisions on priorities for storage use.

The potential of seasonal pumped hydropower storage (SPHS) plant to fulfil future energy storage requirements is vast in mountainous regions. Here the authors show that SPHS costs vary from 0.007 to 0.2 US$ m⁻³ of water stored, 1.8 to 50 US$ MWh⁻¹ of energy stored and 0.37 to 0.6 US$ GW⁻¹ of installed power generation capacity.

Many people globally still use solid fuels for cooking and heating, leading to programmes designed to subsidize cleaner alternatives. This study analyses possible effects of climate mitigation policies on fuel costs and hence the effectiveness of such schemes.

Using subnational Demographic and Health Survey data from 75 low and middle-income countries, the authors show that many households lack access to decent living standards as basic prerequisites for human well-being. Major inequalities exist within and across countries and by socio-economic backgrounds.

To evaluate the effectiveness of current national policies in achieving global temperature targets is important but a systematic multi-model evaluation is still lacking. Here the authors identified a reduction of 3.5 GtCO₂ eq of current national policies relative to a baseline scenario without climate policies by 2030 due to the increasing low carbon share of final energy and the improving final energy intensity.

Achieving transport decarbonization targets depends on vehicle-purchasing decisions. Non-financial consumer preferences presented in six global energy-economy models reveal that diverse policies targeting vehicle buyers are necessary for the widespread adoption of clean technologies.

Contrary to the hopes of policymakers, fossil fuel subsidy removal would have only a small impact on global energy demand and carbon dioxide emissions and would not increase renewable energy use by 2030.

Modelling that integrates the effects of uncertainties in relevant geophysical, technological, social and political factors on the cost of keeping transient global temperature increase to below certain limits shows that political choices have the greatest effect on the cost distribution.

The ‘pathway’ the world needs to follow to limit global temperature rise to 2 °C remains uncertain. Analysis that takes technical and economic constraints on reducing emissions into account indicates that emissions need to peak in the next decade and then fall rapidly to have a good chance of achieving this goal.

Modelling of over 25,000 hydro- and thermoelectric power plants shows water constraints are likely to severely reduce usable capacity after 2040. Fuel switching, increasing efficiency and new cooling systems can reduce power plants’ vulnerability.

Representative Concentration Pathways (RCPs) play a central role in assessments conducted by the climate modelling community. This study comprehensively assesses air pollution emissions in the RCPs and provides projections for air pollutants over the 21st century. Such projections should increase understanding of the range of possible impacts of air pollutants on the climate.

The net-zero transition will bring co-benefits to various sectors but also potential trade-offs that could undermine sustainable development efforts. A study shows that in China, the co-benefits from the transition alone will not secure a sustainable energy–food–water–air quality system.

Raising basic living standards and growing affluence aren't equivalent, and neither are their respective climate impacts.

The Indus river basin in South Asia is water stressed, energy insecure and intensively farmed, and research on this region often lacks a systemic approach to the issues. This study shows how the path to development in the region could be made less costly and more environmentally friendly by fostering transboundary cooperation.

Currently, no comprehensive scientific methodology of corporate risk quantification, in response to new disclosure regulations, has been proposed in the literature. Here we develop fundamental principles that are important for the appropriate use of climate scenario science in transition risk assessments.

The pledges put forward by each country to meet the goals of the Paris Agreement are ambiguous. Rogeljet al. quantify the uncertainty arising from the interpretation of these pledges and find that by 2030 global emissions can vary by −10% to +20% around their median estimate of 52 GtCO₂e yr⁻¹.

Climate impact models have a limited ability to represent risks to the poor and vulnerable. Wider adoption of best practices and new model features that incorporate social heterogeneity and different policy mechanisms are needed to address this shortcoming.

Current emissions scenarios include pathways that overshoot the temperature goals set out in the Paris Agreement and rely on future net negative emissions. Limiting overshoot would require near-term investment but would result in longer-term economic benefit.

Meeting the Paris Agreement targets requires deep emissions reductions supported by a scale-up in carbon dioxide removal. However, current country-reported mitigation pledges are off track to meet carbon dioxide removal needs, unless countries dramatically reduce emissions consistent with low-energy-demand scenarios.

Aligning the IPCC-assessed mitigation pathways with the national greenhouse gas inventories shows that key global mitigation benchmarks become harder to achieve, requiring achieving earlier net-zero and lower cumulative emissions.

Delaying climate mitigation requires large-scale carbon dioxide removal (CDR) in the second half of this century, with possible adverse effects. Under scenarios with no dependence on CDR technologies, this study examines the short- and long-term implications of climate mitigation for land-use and food systems.

The scale and nature of energy investments under diverging technology and policy futures is of great importance to decision makers. Here, a multi-model study projects investment needs under countries’ nationally determined contributions and in pathways consistent with achieving the 2 °C and 1.5 °C targets as well as certain SDGs.

Projects are under way for direct-current ultra-high-voltage transmission lines that would allow trading of renewable electricity across world regions. Guo et al. use integrated assessment models to explore different scenarios for the operation of these projects and assess their potential for decarbonization.

Major shifts in the structure, the levels and the locations of energy use were observed during COVID-19 lockdowns. However, uncertainty remains about the persistence and thus the long-term effects of these changes on the energy system. Kikstra et al. now present various energy scenarios that build on observed changes in energy use to achieve a low-emission global future.

Comprehensive policy measures are needed to close the emissions gap between Nationally Determined Contributions and emissions goals of the Paris Agreement. Here the authors present a Bridge scenario that may aid in closing the emissions gap by 2030.

Mitigation pathways allowing for temperature overshoot often ignore the related climate and macroeconomic impacts. Net-zero pathways with limited overshoot could reduce low-probability high-consequence risks and economic loss.

Urgent action is needed to ensure food security and mitigate climate change. Through a multi-model comparison exercise, this study shows the potential negative trade-offs between food security and climate change mitigation if mitigation policies are carelessly designed.

Residual CO₂ emissions from fossil fuels limit the likelihood of meeting the goals of the Paris Agreement. A sector-level assessment of residual emissions using an ensemble of IAMs indicates that 640–950 GtCO₂ removal will be required to constrain warming to 1.5 °C.

Fundamental value judgments about acceptable maximum levels of climate change and future reliance on controversial technologies can be made explicitly in climate scenarios, thereby addressing the intergenerational bias present in the scenario literature.

Scenarios that constrain end-of-century radiative forcing to 1.9 W m^–2, and thus global mean temperature increases to below 1.5 °C, are explored. Effective scenarios reduce energy use, deploy CO₂ removal measures, and shift to non-emitting energy sources.

COP21 led to a global commitment to decarbonization before 2100 to combat climate change, but leaves the timing and scale of mitigation efforts to individual countries. Here, the authors show that global carbon emissions need to peak within a decade to maintain realistic pathways for achieving the Paris Agreement.

A relatively wide range of emissions in 2020 could keep open the option of limiting long-term temperature increase to below 2 °C; however, a shortfall in critical technologies would narrow that range or eliminate it altogether. Reduced emissions in 2020 would hedge against this uncertainty.

The recent drop in oil prices is having a profound impact on global energy markets, raising questions about how these markets might evolve over the long term. This study uses scenarios to assess the energy and emissions impacts of diverging oil price futures and which uncertainties they depend upon.

An ethically-based method for allocating climate change mitigation effort among subsidiaries, applicable worldwide, is proposed. Applied to the EU Green Deal, this results in a wider range of targets than the Commission’s proposal of 2021.

Future emissions scenarios for the IPCC Sixth Assessment Report should explore the carbon budget space in a systematic manner, which would be robust to the updates of latest climate science, so that policy implications can be adequately assessed.

Scenarios have supported assessments of the IPCC for decades. A new scenario ensemble and a suite of visualization and analysis tools is now made available alongside the IPCC 1.5 °C Special Report to improve transparency and re-use of scenario data across research communities.

Although nearly all 2 °C scenarios use negative CO₂ emission technologies, only relatively small investments are being made in them, and concerns are being raised regarding their large-scale use. If no explicit policy decisions are taken soon, however, their use will simply be forced on us to meet the Paris climate targets.