The Paris Agreement long-term temperature goal of limiting warming to 1.5°C sets ambitions for global climate action to avoid the most devastating impacts of climate change. However, due to past and present climate inaction, exceeding a global mean temperature increase of 1.5°C above pre-industrial levels has become almost inevitable. This has led to an increased interest in so-called overshoot pathways that exceed a global warming level before returning to or below 1.5°C in the long-run, commonly facilitated by deploying carbon dioxide removal methodologies that potentially enable net-negative emissions.
These prospects raise important questions in relation to Earth system feedbacks under overshoot pathways such as: How will Earth System processes evolve under overshoot pathways? 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 level at some later date?
Further, it is important to understand the feasibility and side-effects of large-scale deployment of carbon dioxide removal that are necessary to return the Earth system to safer temperatures post-overshoot: What would it take to pursue such an overshoot pathway and what are the climatic, economic and ecological consequences of large-scale CDR?
In this session, we welcome abstract submissions on global climate dynamics under peak and decline pathways, on regional to global climate impacts in overshoot scenarios, and mechanisms of non-linearity, particularly the risk of rapid/abrupt Earth system change. We welcome Integrated Assessment, Earth system and impact model experiments focused on overshoot pathways, including investigation of carbon dioxide removal, and realization of warming in overshoot pathways with Earth System Models. We also invite analysis focusing on consequences in a wide range of sectors, from ocean dynamics to the cryosphere, biodiversity and biosphere changes to human systems and economic consequences of overshoot. Contributions that consider the socio-economic conditions and feasibility of overshoot scenarios, climate effects of large-scale carbon dioxide removal, as well as the implications of overshoots for climate change adaptation planning are also strongly encouraged.