New global emission scenarios: changes in the highest and lowest scenarios

In a publication in Geoscientific Model Development, a group of climate scientists as part of CMIP7 describes a new set of global emissions scenarios that will form the basis for much climate research in the coming years. Two important changes are that the highest global emissions scenario is now lower than in previous scenario sets, while the lowest emissions scenario no longer remains below 1.5°C. The first change is, among others, due to renewable energy having become more competitive. However, this certainly does not mean that the severe consequences of climate change have been avoided. The new high-end scenario still leads to substantial climate change, while uncertainties in the climate system mean that global warming could still exceed 4°C by 2100. The fact that the low-emissions pathways have become less favorable means that the Paris Agreement target of 1.5°C is no longer achievable without a temporary overshoot.

New Global Emission Scenarios

In climate research, scenarios play an important role in exploring the possible long-term consequences of current choices and trends. They are used, for example, to estimate the consequences of current policies, assess the risks of so-called worst-case scenarios, and determine what would be needed to prevent extreme climate change. Developing these scenarios requires collaboration among research groups worldwide. Therefore, CMIP does coordinate decisions on jointly developing scenarios based on the latest scientific insights, within the framework of the Climate Model Intercomparison Project (CMIP).

The design of the scenarios for CMIP7 was published in April 2026 in Geoscientific Model Development by Van Vuuren et al (2026). The set contains seven scenarios that will form the backbone of global climate research in the coming years. The scenarios are formulated as emissions pathways. In the coming years, they will be analyzed in detail to determine the consequences of climate change. There are several notable changes: the highest emissions scenario is now lower than in the previous scenario set, while — on the other hand — the lowest scenario is no longer as low as before.

Scenarios developed in a long process

The development of the new CMIP scenarios started in June 2023 with a first workshop in Reading. About 40 scientists, from different climate science disciplines, participated in this workshop in person and another 40 online. After the workshop, a Scientific Steering Committee was established based on an open call and including 20 scientists representing knowledge on emission and land use trends the climate system and climate impacts. The original design for the experiments was published late 2023 and subject to peer review. Based on this, a revised version of the experimental design was submitted to Geoscientific Model Development and again made available for open-access review. The paper got finalized April 2026. The design formed the basis of quantification by Integrated Assessment Model teams. Their data output has been shared with the climate modelling community.

New elements

The scenarios cover a range from low to high emissions. For the first time, Earth System Models capable of doing this, will run the experiments based on emission pathways (and not based on concentrations) allowing more insights into relevant uncertainties. The set also contains a several overshoot scenarios. The range of emission scenarios for the 21st century is more constrained than earlier experiments.

Emissions in the highest scenario lower than the earlier scenarios in CMIP5 and CMIP6…

The highest emissions scenario serves as a basis for exploring the possible consequences of climate change if everything develops unfavorably. It is important to ensure that society is also prepared for undesirable developments. This highest scenario assumes a world with extensive use of fossil fuels. The new highest scenario results in lower emissions than the previous highest scenario (also known as RCP8.5 or SSP5-8.5). There are three main reasons for this. First, emissions in recent years have largely followed the middle-of-the-road scenario. This alone results in lower new projections. Second, the contribution of renewable energy has grown much faster than expected in recent years due to declining costs. As a result, expectations are that fossil fuel use will no longer continue to increase rapidly. Finally, although still limited, climate policy is being implemented.

… but warming above 4°C remains possible

Although emissions in the highest CMIP7 scenario are lower this century than in the previous version (CMIP6), this does not mean that high-impact climate change has been avoided. First, the expected warming in this scenario is still around 3.5°C above the pre-industrial level — a level at which very severe climate impacts are expected. But it is important to also take into account that the sensitivity of the climate system may be higher than our best estimate or that there are stronger feedbacks on the carbon cycle. In that case, global temperature increase could still easily exceed 4°C. Because global temperatures have risen more rapidly in recent years than expected, such a strong temperature increase certainly cannot be ruled out. In addition, temperatures in the high-emissions scenario continue to rise after 2100, with the level previously projected for 2100 expected to be reached around 2150.

There are no longer any scenarios that remain below 1.5°C

At the lower end of the range, several scenarios explore what is needed to prevent dangerous climate change and meet the goals of the Paris Agreement. Previously, it was still possible to design emissions pathways that kept warming around 1.5°C. Because emissions have continued to rise in recent years, this is no longer possible. Even the most optimistic scenarios only return to around 1.5°C by the end of this century, after a substantial overshoot of at least 0.2 to 0.3°C. This means that greater attention will need to be paid to climate impacts and climate adaptation. In addition to intensive emissions reductions, efforts will also need to focus on removing CO₂ from the atmosphere.

Further Research

The climate scenarios will be further examined in climate studies around the world in the coming years in order to assess the possible consequences of climate change. Ultimately, the emissions scenarios, the outputs of climate models, and assessments of climate impacts will be used in the next Intergovernmental Panel on Climate Change (IPCC) report, which is expected to be published in 2028/2029.
 

Article

Van Vuuren, D. P. and O'Neill, B. C. Tebaldi, C. et al. (2026), 'The Scenario Model Intercomparison Project for CMIP7 (ScenarioMIP-CMIP7)', Geoscientific Model Development 19. 7, pp. 2627—2656, https://doi.org/10.5194/gmd-19-2627-2026