Tipping points in the climate system

In climate science, a tipping point is a critical threshold that, when crossed, leads to large and often irreversible changes in the climate system. If tipping points are crossed, they are likely to have severe impacts on human society. Tipping behavior is found across the climate system, in ecosystems, ice sheets, and the circulation of the ocean and atmosphere. Tipping points are often, but not necessarily, abrupt. For example, with average global warming somewhere between and , the Greenland ice sheet passes a tipping point and is doomed, but its melt would take place over millennia. Tipping points are possible at today's global warming of just over above preindustrial times, and highly probable above of global warming. The geological record shows many abrupt changes that suggest tipping points may have been crossed in ancient times. It is possible that some tipping points are close to being crossed or have already been crossed, like those of the West Antarctic and Greenland ice sheets, the Amazon rainforest and warm-water coral reefs. A danger is that if the tipping point in one system is crossed, this could cause a cascade of other tipping points, leading to severe, potentially catastrophic, impacts. Abrupt climate change The sixth report from the United Nations Intergovernmental Panel on Climate Change (IPCC), released in 2021, defines a tipping point as a "critical threshold beyond which a system reorganizes, often abruptly and/or irreversibly". It can be brought about by a small disturbance causing a disproportionately large change in the system. It can also be associated with self-reinforcing feedbacks, which could lead to changes in the climate system irreversible on a human timescale. For any particular climate component, the shift from one state to a new stable state may take many decades or centuries. The 2019 IPCC Special Report on the Ocean and Cryosphere in a Changing Climate defines a tipping point as: "A level of change in system properties beyond which a system reorganises, often in a non-linear manner, and does not return to the initial state even if the drivers of the change are abated.