Earth System Tipping Points
The Brief stresses that tipping of any major Earth system would have catastrophic impacts on humans and the planet. The interaction of these systems can lead to destabilising cascades, meaning that irreversible change can spread from one Earth sub-system to many. Even without crossing tipping points, major societal impacts of climate change are already occurring and likely to become more intense and widespread. Emerging scientific evidence around Earth system tipping points increases the urgency of climate change mitigation while also prioritizing resilience and adaptation strategies. Tipping points require approaches that can better anticipate risks and make decisions even when there is a high level of uncertainty. Building capacities to gather and synthesize a wide range of scientific information about Earth system change will help leaders balance the risks of different climate and environment pathways.
Earth system tipping points are critical limits in the Earthʼs climate and planetary sub-systems (e.g. rainforests and ice sheets) where small additional changes can trigger major and potentially irreversible shifts that continue on their own. These shifts are driven by internal feedback processes and may be difficult or impossible to reverse on human timescales, even if the original pressures (such as greenhouse gas emissions) are reduced or eliminated.
There are varying degrees of scientific certainty concerning which sub-systems may be approaching critical thresholds and how soon large-scale irreversible change could occur. In general, the probabilities of reaching tipping points rise significantly as global warming increases.
Despite this uncertainty, there are improved methods and growing scientific evidence that several key Earth sub-systems are at increasing risk of reaching (or have already begun crossing) tipping points, including: the long term melt of large polar continental ice sheets ; the widespread loss of warm-water coral reefs ; the shift of parts of the Amazon rainforest to savanna-like conditions; the weakening or collapse of deep-water formation/ circulation processes in the oceans.
