The IPCC defines key risks related to climate change as potentially severe risks that are relevant to the primary goal of the United Nations Framework Convention on Climate Change treaty to avoid 'dangerous human interference with the climate system', and whatever the scale considered . What constitutes 'dangerous' or 'severe' risks is partly a value judgement and can therefore vary widely across people, communities or countries. However, the severity of risks also depends on criteria like the magnitude, irreversibility, timing, likelihood of the impacts they describe, and the adaptive capacity of the affected systems . The Working Group Il authors use these criteria in various ways to identify those risks that could become especially large in the future owing to the interaction of physical changes to the climate system with vulnerable populations and ecosystems exposed to them. For example, some natural systems may be at risk of collapsing, as is the case for warm-water coral reefs by mid-century, even if global warming is limited to +1.5℃. For human systems, severe risks can include increasing restriction of water resources that are already being observed; mortality or economic damages that are large compared with historical crises; or impacts on coastal systems from SLR and storms that could make some locations uninhabitable.
IPCC
Climate Change 2022: Impacts, Adaptation and Vulnerability
IPCC Report