We Climate Scientists Won’t Know Exactly How the Crisis Will Unfold Until it’s Too Late

One such tipping event, the unravelling and eventual disappearance of the Amazon rainforest, may already be underway. A new study uses model-aided statistical analysis from past ecosystem collapses and comes to the conclusion that, once triggered, Amazon dieback could take as little as 50 years. Because we lack a full understanding of how exactly such a collapse might unfold, such models are not being included in future projections.

The IPCC’s recent report on the oceans and cryosphere (sea ice, glaciers and ice sheets) still doesn’t report the full possible range of sea level rise exacerbated by a possible collapse of the West Antarctic ice sheet. The IPCC’s range of 0.3 to 1.1 meters by 2100, dependent on emissions scenario, stays markedly below the worst-case scenario of 2.4 meters which resulted from an analysis of experts’ opinions. Zita Sebesvari, one of the report’s lead authors, has admitted that such a worst case scenario cannot be ruled out.

We know quite well that the climate we are about to create resembles that of millions of years ago, but we are mostly ignorant about how fast this will happen and what it means for humans and ecosystems. Yet scientists rarely point out the uncertainties in their predictions – in particular worst-case scenarios that are beyond the capability of models – and prefer to stick to the conservative but firm conclusions that can be drawn from well-established models.

To discuss highly uncertain but potentially catastrophic outcomes is often seen as political fearmongering. But basing the political response to the climate crisis on a series of safe-looking and – in their totality – apparently certain predictions is therefore painting a wholly inadequate picture of the potential risks that the climate and ecological crises pose to humanity and the biosphere.

We scientists need to proactively emphasize the uncertainties of our model scenarios, and that we don’t know for certain how severe the climate crisis will be, how rapidly it could unfold, nor how it will affect humans and ecosystems. In so doing, we must reassess how best science can contribute to climate policy in service of humanity.

We must have the humility to accept how much we do not know – including at what point it is too late to prevent catastrophic tipping points and the consequent large-scale disruption. Only then can we free the political response from operating according to conservative assumptions and mid-range scenarios, and base it firmly on preventing a worst-case scenario.

Wolfgang Knorr is Senior Research Scientist, Physical Geography and Ecosystem Science, Lund University. Will Steffen is Emeritus Professor, Australian National University. This article is published courtesy of The Conversation.