The global mean temperature in 2023 was almost 1.5 ˚C higher than preindustrial values; and temperatures in 2024 might even exceed 1.5 ˚C for the first time for an entire calendar year. Although this warming is partly explained by internal variability, it is now almost certain the 1.5 ˚C target of the Paris Agreement will be exceeded, and even higher warming levels will be breached unless greenhouse gas emissions are rapidly reduced in the coming decades.
It is therefore important to improve our understanding of the risks associated with exceeding such global warming levels, as well as investigate plausible pathways that result in global cooling, returning the Earth back to a safer temperature level at some later date. Key questions include; what feedbacks might occur once specific warming targets are exceeded and will these feedbacks make returning to a lower global temperature level more difficult? What is the likelihood of rapid or abrupt change (including tipping points) occurring due to overshoot? What are the consequent risks for society and the natural environment? And, how reversible will these changes be if global mean temperature returns to a lower temperature level at some later date?
In addition, it is of the utmost importance to assess different negative emission pathways, such as those driven by Carbon Dioxide Removal (CDR) actions, that are necessary to return the Earth system to safer temperatures post-overshoot, focusing on the plausibility and efficacy of such pathways, including portfolios of CDR options, as well as any resulting climate, societal or environmental impacts.
We welcome:
- Integrated Assessment, Earth system and impact model experiments focused on overshoot pathways, including investigation of CDRs, their interaction with the global climate and carbon cycle, and potential societal and environmental impacts.
- Realization of warming overshoot pathways with Earth System Models (including idealized pathways such as suggested by TIPMIP) and analysis of the consequences of overshoot on climate, particularly the risk of rapid/abrupt Earth system change.
- Assessment of the societal and environmental impacts of overshoot, including impacts resulting from any triggered rapid/abrupt Earth system changes.
- Analysis of the potential reversibility of changes resulting from warming overshoot across the coupled Earth system, society and the ecosystem.