by
David Spratt
Fourth in a
series
A tipping point may be understood as a step change, or passing of a critical threshold, in a major earth-climate system component, where a small perturbation (a small push or change) unleashes a bigger change in the component. Potsdam Institute Director, Prof. Hans Joachim Schellnhuber,
says that tipping points “identify the most vulnerable components (tipping elements) of the Earth System, the critical warming thresholds where the respective Earth System elements flip into a qualitatively new state”. These elements include ecosystems, major ocean and atmospheric circulation patterns, the polar ice sheets, and the land- and ocean-based carbon stores.
This process is often tied to positive feedbacks, where a change in a component leads to other changes that eventually “feed back” onto the original change to amplify it. The classic case in global warming (or, in reverse, cooling) is the ice-albedo feedback, where decreases (increases) in the ice cover area change surface reflectivity (albedo), trapping more (less) heat and producing further ice loss (gain).