Issue Rising risk of crossing Earth-system tipping points and cascades

Summary

A tipping point is a threshold at which a large Earth-system component shifts from absorbing disturbances to amplifying them in a new state, and planetary boundaries act as warning signs placed before such hazards. The report finds that the risk of crossing several tipping thresholds rises substantially between about 1 and 2°C of warming above pre-industrial levels, and judges that warm-water coral reefs are probably already tipping. Tipping elements such as the Atlantic overturning circulation, polar ice sheets, permafrost, the Amazon and boreal forests influence one another. A major review of climate tipping interactions concluded that links among ice sheets, ocean circulation, forests, monsoons and permafrost are mostly destabilizing, and cascades cannot be ruled out. Recent results also suggest major Antarctic ice masses may already have begun sliding into the ocean. Crossing a boundary does not guarantee tipping, but each breach raises the risk and further narrows the safety margin.