This is a schematic picture of the climate represented by the red ball. The climate can be located in two different states, the two valleys on each side of a hill. In the first scenario the climate is like a seesaw. If the outside influences increase or, for example, increased CO2 makes the weight heavier on the other side, the seesaw will tip forcing the climate over into the other state. The climate change would be predictable. In the second scenario, the hill is fixed and a series of small chaotic kicks from wind and weather could cause it to roll over into the other state. This climate change is unpredictable.
Mathematically speaking, the first scenario is a "bifurcation" and the second scenario "noise-induced transition".
Credit:Peter Ditlevsen, PhD. Dr. Scient.
Centre for Ice and Climate, Niels Bohr Institute, University of Copenhagen