Overshoot: Communicating the risks of exceeding and returning to a 1.5°C level of global warming

Effective communication is crucial in preparing researchers and policymakers for decisions related to global warming. As exceeding the 1.5°C threshold becomes inevitable, it's vital that all stakeholders understand the implications and act swiftly. The toolkit will explain the implications of overshoot through the co-design of various materials that use multiple channels to effectively reach target audiences. The visualisations will become stepping stones for understanding, dissemination, and decision-making. They will be the starting point for an ongoing collaboration with leading climate scientists. The design process will involve various stakeholders at different stages. The visualisations will be standalone yet contribute to a unified narrative, introducing the concept of overshooting and its implications - enabling next steps in a continuing communication challenge. The paper “Overshoot: A Conceptual Review of Exceeding and Returning to Global Warming of 1.5°C” presents: - 8 key insights, - 4 future challenges, and - 5 visuals that explain the climate, technology, economy, and policy effects of different global warming overshoot scenarios. The study is written by Andy Reisinger, Jan S. Fuglestvedt, Anna Pirani, Oliver Geden, Chris D. Jones, Shobha Maharaj, Elvira Poloczanska, Angela Morelli, Tom Gabriel Johansen, Carolina Adler, Richard A. Betts, and Sonia I. Seneviratne. It was published in Annual Review of Environment and Resources 2025, Volume 50, pages 1.1–1.33. Read the paper here: https://doi.org/10.1146/annurev-environ-111523-102029 A digital platform by CMCC builds on the paper and offers an easy-to-understand version, helping users explore the complex topic of overshoot. This platform connects science, policy, the environment, society, and economics, and is likely to influence climate discussions in the future: Visit the platform here: https://overshoot.cmcc.it

The overshoot concept is important to understand as a key policy challenge with far-reaching implications for global climate adaptation and mitigation strategies. - An international research team presents a comprehensive framing of the concept to understand different warming futures, the related mitigation options to bring temperatures down, how the Earth system responds to climate-related risk, as well as the adaptation needs and feasibility. - 8 key takeaways, 4 future challenges, and 5 figures that portray the climate, technological, economic, and policy implications of various overshoot pathways. The results are presented in the paper “Overshoot: a conceptual review of exceeding and returning to global warming of 1.5°C”, Andy Reisinger, Jan S. Fuglestvedt, Anna Pirani, Oliver Geden, Chris D. Jones, Shobha Maharaj, Elvira Poloczanska, Angela Morelli, Tom Gabriel Johansen, Carolina Adler, Richard A. Betts, Sonia I. Seneviratne. https://doi.org/10.1146/annurev-environ-111523-102029 - A digital information platform hosted by CMCC expands on the paper’s insights, offering a plain language narrative to navigate this complex issue - one that will shape climate discussions in the years to come, bridging science, policy, environment, society, and economics. https://overshoot.cmcc.it/ An International, multidisciplinary team of renowned scientists and experts The team behind this research is composed of high-profile experts from top institutions around the world. Several authors served or are serving as vice-chairs of one of the IPCC’s Working Groups, while others served as authors of a range of IPCC reports. CMCC’s Anna Pirani, one of the paper's authors, also has an extensive background in the IPCC, including being the Head of the Working Group I Technical Support Unit of AR6 and now the alternate IPCC Focal Point for Italy. The team includes contributors from prestigious institutions such as CICERO in Norway, the German Institute for International and Security Affairs, the Met Office in the UK, the University of Bristol, the University of Fiji, the Institute for Small Islands, the Alfred Wegener Institute for Polar and Marine Research, the Mountain Research Initiative, the University of Bern, the Global Systems Institute at the University of Exeter, and ETH Zurich. The paper’s graphical material was co-designed with the team of authors, led by Angela Morelli and Tom Gabriel Johansen of Info Design Lab.

Current insufficient global action on reducing greenhouse gas emissions makes it almost certain that global warming will exceed 1.5°C within the next decade. Limiting warming to 1.5°C long-term is still possible if we prepare for a temporary exceedance, known as 'overshoot,' and take actions to stabilise and eventually reduce global temperatures. Deciding whether to overshoot and then reduce to 1.5°C, or to stabilise above 1.5°C, will depend on clear information about the climate-related impacts and risks avoided, and the additional mitigation options and efforts needed. It is crucial for researchers and policymakers to start discussing these scenarios and what they mean for immediate action. Effective communication of this topic is essential to align global actions. The purpose is to co-design the toolkit in a participatory way through a multi-stakeholder approach, aiming to provide a very specific audience of scientists to efficiently engage into a much-needed conversation to be had. A multidisciplinary team of leading scientists, information designers, and communication experts will leverage their previous experience and groundbreaking work on co-designing communication tools for decision-making to create a solid foundation for the proposed project. Co-design encapsulates a way of approaching data visualisation that ensures a deep and shared understanding between those creating the visuals and the audience, with the goal of staying rigorous to the science while meeting the audience’s needs through engagement, clarity, and beauty. When such a human-centred methodology is at the heart of the design activities, the design process flows across different deliverables and teams. This means milestones and plans can be achieved, ensuring maximum participation of all stakeholders. The work is characterised by inclusiveness, with the ability to break down barriers across disciplines and to ensure the collaboration and knowledge-sharing across the project's ecosystem.