Convening of a joint WCRP/IPCC workshop on "High-impact events, tipping points and their consequences"
The World Climate Research Programme (WCRP) and the IPCC - Intergovernmental Panel on Climate Change (IPCC) are joining forces to convene a workshop on "High-impact events, tipping points and their consequences" in Paris, France, from 26-28 November. The workshop will bring together leading experts from around the globe, covering many disciplines, in support of the 7th IPCC Assessment Report (AR7) process.
In December 2024, over 220 experts and IPCC Bureau Members from more than 70 countries met in Kuala Lumpur, Malaysia, for the Scoping Meeting of the Working Group Contributions to the AR7 . For Working Group I, which examines the physical science underpinning past, present and future climate change, the agreed outline includes a chapter on "Abrupt changes, low-likelihood high-impact events and critical thresholds, including tipping points, in the Earth system", with related topics also relevant to other chapters across the AR7. The decision to include a chapter on this topic is a recognition by IPCC Members that it is essential that an authoritative assessment of this topic is completed.
While it is known that the Earth system has gone through rapid and near-term irreversible changes in the past, the kind of abrupt shifts we can expect in the future is uncertain. Research into severe climate events and tipping points has grown substantially in recent years, but there is still a lack of consensus on many aspects, including methodologies, critical thresholds, and the likelihood of such events occurring. There is large uncertainty as to what extent such events can be captured in Earth system models and what metrics are best to represent such changes or a decreasing resilience of a system at risk of tipping. In addition, there is confusion about timing. When is a system committed to a nonlinear transition, and how does this relate to when the change actually happens? Are these changes permanent, or can they be reversed if global temperature is reduced?
Debate also continues over whether we can observe signs of approaching tipping points before they happen or predict them, which is a critical question for early warning capabilities. In tandem, there is growing attention on the closely related topic of rare but high-impact risks-called "tail risks" and cascading shocks. Severe outcomes may not be the most likely ones, but they need to be assessed since they would have a disproportionate impact on climate risk to society and economic risk due to their consequences.
Professor Thomas Stocker (University of Bern, Switzerland), who is also a WMO Science Advisory Panel Member, began advocating for an IPCC Special Report on Climate Tipping Points in 2020. While his bid was unsuccessful, his work raised awareness of the need for this type of effort. In early 2024 WCRP initiated a High-impact climate events, tipping points, and irreversible regional impacts assessment paper to review the current understanding and provide recommendations for how Earth system models can be improved to better understand the processes involved and to identify potential early warnings. This effort is led by Professor Gabi Hegerl (University of Edinburgh, UK) and currently includes over 70 experts on these topics, and is in its drafting stage.
The WCRP assessment was designed to feed into AR7, but it soon became clear early in the IPCC process that consensus building would be important. This led to agreement between WCRP and the IPCC Working Group I Co-Chairs to jointly convene a workshop on the topic. In order that it can directly feed into the first IPCC Lead Author Meeting (1-5 December, Paris), which includes all three IPCC Working Groups, it will be held immediately prior to that event in the same location (26-28 November 2025, Paris). The workshop will be by invitation only and will by design include a strong representation of Global South researchers and diverse perspectives, including in the authors selected to lead and contribute to relevant Chapters of the AR7.
