In the cryosphere, one of the most immediate risks is to the Greenland ice sheet. Recent evidence suggests that this system could be near its tipping point, with about 7 metres of sea level rise likely to ensue over the coming centuries.6 However, as with all tipping points, limited real-world data combined with the weaknesses of current climate models leave a high degree of uncertainty over exactly how much of a “push” is required.
Models also show that the Amazon rainforest can irreversibly “flip” from a forest to a savannah. This would be a catastrophic shift, accelerating climate change7 and fuelling more warming.8 The permafrost regions of the far north are also thought to be a tipping element, and recent studies indicate this tipping point may be closer than thought.9 Collapse of the permafrost will release large quantities of greenhouse gases, accelerating and increasing the warming trend.
The current generation of Earth system models struggle to adequately resolve these tipping elements in many cases.10 Some models omit them entirely, making the accurate inclusion of tipping elements an important focus for reducing the ambiguity of model-based climate predictions. The best-modelled tipping elements are those, like the Greenland ice sheet, that primarily depend on inanimate physical objects: tipping elements that include biosphere components, such as the Amazon, are a significantly bigger challenge and require substantial ground-truthing with observations.