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Incoherent new climate-policy messages by Prime Minister Rishi Sunak will dissolve the UK’s climate leadership, stifle innovation’s momentum and cost consumers.

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.

Current national emissions targets can't limit global warming to 2 °C, calculate Joeri Rogelj, Malte Meinshausen and colleagues — they might even lock the world into exceeding 3 °C warming.

Breaking away from the utopian assumption that the international community will agree on a single emissions allocation scheme, this study assesses approaches to setting country-level mitigation targets in line with the 2 °C goal.

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.

Scenario ensembles are widely used in climate change research, while their opportunistic nature could lead to biased outcomes in following analysis. Focusing on relevance, quality and diversity, researchers develop a simple and transparent weighting framework to address these challenges.

Reduced GHG and air pollutant emissions during the COVID-19 lockdowns resulted in declines in NO_x emissions of up to 30%, causing short-term cooling, while ~20% SO₂ emissions decline countered this for overall minimal temperature effect.

A scientific foundation is required to establish nations’ responsibilities in a hotter ‘overshoot’ world.

Carbon dioxide removal (CDR) plays an important role in decarbonization pathways to meet climate goals, but some methods are land-intensive. Multimodel analysis reveals conflicts between biodiversity and CDR that are distributed unevenly, and shows that synergies are crucial to meet climate and conservation goals.

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.

An assessment of allowable carbon emissions that factors in multiple climate targets finds smaller permissible emission budgets than those inferred from studies that focus on temperature change alone. See Letter p.197

There is a mismatch between emission estimates from global land use calculated from IAMs and countries’ greenhouse gas inventories. This study presents a method for reconciling these estimates by reallocating part of the land-use sink, facilitating progress assessment towards climate goals.

Mitigation pathways tend to focus on an end temperature target and calculate how to keep within these bounds. This work uses seven integrated assessment models to consider current mitigation efforts and project likely temperature trajectories.

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.

Trends in global H₂ sources and sinks are analysed from 1990 to 2020, and a comprehensive budget for the decade 2010–2020 is presented.

Land-based carbon dioxide removals are critical for meeting the low-warming targets, yet their availability is limited when avoiding excessive risks to sustainability. Scenario-based analysis suggests that they should only be used to compensate for emissions from hard-to-abate sectors and overshoot.

A temporary breach of the temperature target, or overshoot, is unavoidable. The authors review the history of how overshoot evolved in mitigation pathways, the magnitude and outcomes of potential physical and socio-economic impacts, and priorities for future model and scenario development.

Equity is central to international climate policy, but quantifications often only look at carbon dioxide. This study allocates a global warming budget for all greenhouse gases and shows most developed and advanced economies have already exceeded their fair share.

Current pledges for emissions cuts are insufficient to meet the Paris Agreement temperature goal. The wave of net zero targets being discussed and adopted could make the Paris goal possible if further countries follow suit.

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.

National targets give virtually no chance of constraining warming to 2 °C and no chance of protecting coral reefs.

To limit warming, action plans from countries and companies must be fair, rigorous and transparent.

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 ‘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.

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.

Models and scenarios on which climate projection are based vary between IPCC reports. To facilitate meaningful comparison, this study provides probabilistic climate projections for different scenarios in a single consistent framework, incorporating the overall consensus understanding of the uncertainty in climate sensitivity, and constrained by the observed historical warming.

New synthesis shows what a wasted decade means for the climate pact made in Paris.

The adoption of the Paris Agreement is a historic milestone for the global response to the threat of climate change. Scientists are now being challenged to investigate a 1.5 °C world — which will require an accelerated effort from the geoscience community.

Current best estimates of the remaining carbon budgets to meet the Paris Agreements goals assume substantial reductions in methane and other non-CO₂ greenhouse gases, and failure to achieve these reductions could place the goals out of reach.

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.

Side events of annual UNFCCC Conferences of Parties are one of several channels by which non-state actors influence climate negotiation. By analysing discourse and networks of actors, this research examines how topics evolve over time and how energy interest groups gain access to agenda setting.

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.

To align their portfolios with the Paris Agreement, investors need to know the emissions of companies they invest in. Estimating these should start from a precautionary principle that disincentivizes free-riding and protects the planet.

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.

Temporarily overshooting the 1.5 °C limit risks triggering climate tipping elements. This study finds that every 0.1 °C of warming increases risk, with a strong acceleration above +2.0 °C. Achieving net-zero emissions by 2100 is crucial to minimise long-term risks.

The authors combine climate simulations with observations to estimate carbon budgets which are better constrained and find they are more than 10% larger than the mean value from CMIP6 models.

Aiming for declining global temperatures can limit long-term climate risks compared with a mere stabilization of global warming, including sea-level rise and cryosphere changes.

The remaining carbon budget (RCB) is a critical estimate of the carbon that can be emitted while staying within a particular temperature threshold. This study provides an updated assessment of the RCB using recent data and robustness checks to increase confidence in the estimate.

Emerging limitations on climate and low-carbon technology would require adjusting our 15.C climate change mitigation pathways. However, this could increase average annual emissions reductions to around 3GtCO₂/year using a broad portfolio of mitigation measures.