‘Tipping points’ could come this century

Published today by the prestigious international journal Proceedings of the National Academy of Science (PNAS), the researchers have coined a new term, ‘tipping elements’, to describe those components of the climate system that are at risk of passing a tipping point.

The term ‘tipping point’ is used to describe a critical threshold at which a small change in human activity can have large, long-term consequences for the Earth’s climate system.

In this new research, lead author Prof Tim Lenton of the University of East Anglia (UEA) and colleagues at the Postdam Institute of Climate Impact Research (PIK), Carnegie Mellon University, Newcastle University and Oxford University have drawn up a shortlist of nine tipping elements relevant to current policy-making and calculated where their tipping points could lie. All of them could be tipped within the next 100 years.

The nine tipping elements and the time it will take them to undergo a major transition are:

•Melting of Arctic sea-ice (approx 10 years)
•Decay of the Greenland ice sheet (more than 300 years)
•Collapse of the West Antarctic ice sheet (more than 300 years)
•Collapse of the Atlantic thermohaline circulation (approx 100 years)
•Increase in the El Nino Southern Oscillation (approx 100 years)
•Collapse of the Indian summer monsoon (approx 1 year)
•Greening of the Sahara/Sahel and disruption of the West African monsoon (approx 10 years)
•Dieback of the Amazon rainforest (approx 50 years)
•Dieback of the Boreal Forest (approx 50 years)
The paper also demonstrates how, in principle, early warning systems could be established using real-time monitoring and modelling to detect the proximity of certain tipping points.

“Society must not be lulled into a false sense of security by smooth projections of global change,” said Prof Lenton.

“Our findings suggest that a variety of tipping elements could reach their critical point within this century under human-induced climate change. The greatest threats are tipping of the Arctic sea-ice and the Greenland ice sheet, and at least five other elements could surprise us by exhibiting a nearby tipping point.”

‘Tipping elements in the Earth’s climate system’ by Tim Lenton (UEA and Tyndall Centre), Hermann Held (PIK), Elmar Kriegler (Carnegie Mellon University and PIK), Jim Hall (Newcastle University and Tyndall Centre), Wolfgang Lucht (PIK), Stefan Rahmstorf (PIK) and Hans Joachim Schellnhuber (PIK, Oxford University and Tyndall Centre) is published by PNAS in the week beginning Monday February 4.

The findings are based on a critical review of the literature, the results of a recent workshop held at the British Embassy in Berlin which brought together 36 international experts in the field, and an elicitation exercise involving a further 52 international experts.