Climate simulations data and knowledge for optimal support of IPCC Assessments and International Policy

Project results are expected to contribute to all of the following expected outcomes:

• The institutions in charge of generating the relevant information for decision makers can access and utilise in a timely manner scientifically robust climate projections corresponding to a range of future scenarios and their corresponding greenhouse gas emission pathways, including scenarios matching the Paris Agreement targets;
• Decision makers and society can better understand the impacts, risks and implications of pathways involving different magnitudes and durations of temperature overshoot;
• The European research community provides a coordinated contribution to the IPCC and other major scientific initiatives (e.g., IPBES, WCRP, World Adaptation Science Programme (WASP), the Global Carbon Budget), in support of informing the UNFCCC process and other global, European and national climate efforts;
• The activities of international programmes and communities like the Integrated Assessment Modelling Consortium (IAMC), the CMIP, the CORDEX and Inter-Sectoral Impact Model Intercomparison Project (ISIMIP) are better coordinated between each other, with outcomes more consistent and responding to policy needs better and in a timelier manner;
• The European contribution to these programmes is supported by an improved and interconnected overarching infrastructure.

Given the rapidly developing climate crisis, there is an increasing need for accurate, reliable, and actionable information at global to local spatial scales, and near to long timescales. This information supports a range of requirements, including policy related ones. In particular, simulations and knowledge delivered that feed into the IPCC, including the Seventh Assessment Report (AR7) and later ones, should be internally coherent and well-coordinated. The modelling, setting, ensemble, and simulation design should be suited to meet societal and policy demands to support timelier European and international climate policy developments. This also implies progressing towards an operational framework to provide the best possible information for societal decision-making that brings together available approaches. The resulting simulations and analysis should sample the full spectrum of climate risks. In particular, as global mitigation efforts are presently insufficient and temperatures continue to rise, the impacts of global warming overshoot on the Earth system and the feasibility, possible pace, and implications of bringing global temperatures down in a sustainable way after an overshoot need to be explored. This analysis should also consider the risks and consequences of potential abrupt and irreversible impacts (e.g., sea level rise, changes in ocean circulation, ocean-acidification, water cycle alterations, soil alterations, aridification, species extinctions, loss of sea ice, glaciers, and ice sheets, and crossing climate and ecological tipping points).

Therefore, actions should address all of the following aspects:

• Generate future global climate projections with state-of-the-art Earth System Models (ESM) which are built on the latest improvements in modelling technologies and in process understanding with a more complete representation of climate–carbon cycle feedback;
• Design climate simulations considering the socio-economic scenarios from the most up to date set of Integrated Assessment Models (IAM). Greenhouse gas emission pathways should be provided based on various societal mitigation and adaptation choices and land-use scenarios. Climate feedback should be also considered. The resulting assessment should link allowable carbon emissions with key climate targets, spanning policy relevant temporal and spatial scales;
• Deliver scenarios and simulations with different levels and durations of warming overshoot (to be selected for their policy relevance), assessing the corresponding risks accounting for fast and slow onset processes and the feasibility and limits of carbon dioxide removal methodologies;
• Update and coordinate the assumptions as well as the observational and simulated climate data sets underpinning the models and experiments of the various climate science communities (including Earth system, sectoral impacts, adaptation, and mitigation modellers) across international programmes, such as IAMC, CMIP, CORDEX and ISIMIP, optimising the interaction between them as much as possible within the same IPCC cycle;
• Design a framework to coordinate and incorporate the suite of global and regional climate projections, encompassing the range of available model resolutions and model realism, using consistent concentration and emission-driven ESMs, enhancing collaboration between European Earth system modelling and service provision, such as Copernicus and Destination Earth. This system should include cross-analysis and evaluation of the full suite of models, including approaches for sampling projection and scenario uncertainty (e.g., emulators). The framework should also make the modelling results more accessible and understandable to the practitioners and decision makers;
• Improve the existing infrastructure landscape (software, tools, data, adaptation of models to High-Performance Computing (HPC)), to support the delivery of global and regional climate projections and associated analysis (for which a part of the budget may be allocated, but not more than 30% of the total eligible costs). This should be complementary to efforts funded through the European Research Infrastructures, Euro-HPC Joint Undertaking, Digital Europe Programme and other sources. ESM simulations are intended as the core of the topic with links to other modelling activities. To maximise the policy relevance of the climate simulations delivered, the operationalisation framework and the scenarios should be developed in co-creation with policy makers (e.g., through advisory boards or other participatory procedures).

When dealing with models, actions should promote the highest standards of transparency and openness, as much as possible going well beyond documentation and extending to aspects such as assumptions, protocols, code, and data that is managed in compliance with the FAIR principles^[1].

They should envisage clustering activities with any other relevant projects (in^[2] and outside of Horizon Europe) for cross-projects cooperation and exchange of results. Proposals should earmark the necessary resources for these purposes. As this endeavour should be supported by the research communities that continuously improve the modelling systems and related infrastructure, strong interaction and coordination is expected with the projects funded under previous calls of this Destination and other relevant projects on ESM, with the topic HORIZON-CL5-2025-03-D1-02 “Advancing Earth System Models to increase understanding of Earth system change”, and with the topic HORIZON-INFRA-2025-01-SERV-02 (area on Research infrastructure services to improve the understanding and prediction of future climate changes and its impacts).

International cooperation is encouraged, in particular with the Global South^[3], to promote capacity and consensus building, for example, by training early career researchers from Global South countries (see specific conditions for financial support to third parties). Maximum total amount dedicated to these activities should not exceed EUR 1.000.000.

[1] FAIR (Findable, Accessible, Interoperable, Reusable).

[2] For example, relevant projects funded under the Horizon Europe calls Climate sciences and responses.

[3] In absence of a single formal definition of the Global South, the list of low - to middle- income countries automatically eligible for Horizon Europe funding should be used for this purpose – see the Horizon Europe List of Participating Countries on EU Funding and Tenders Portal for up-to-date information