Nine Tipping Points

Lenton et al., published a paper in the Proceedings of the National Academy of Sciences. Here they identify nine man made possible collapses of our environment. They are:

Greenland Ice Sheet

Arctic sea-ice

West Antarctic Ice Sheet

Boreal forest

Amazon rainforest

El Niño Southern Oscillation

Sahara/Sahel- and West African monsoon

Indian summer monsoon

Atlantic thermohaline circulation

The last one has a 10% chance to occur this century, is the least damaging, and was the basis for the movie, "The Day After Tomorrow"

Click here to get the article:

Tipping elements in the Earth's climate system

Author's Comments:

Statements:

Hans Joachim Schellnhuber:

"This is the first systematic analysis of the tipping elements issue. We have developed a mathematical formalism for describing tipping elements and we have reviewed the complete pertinent literature. We have also identified the tipping elements in the Earth’s climate systems with regard to their relevance for climate policy. One could look at this paper as a “mini-IPCC-report” focusing on tipping elements."


Stefan Rahmstorf on effects on Europe:

"Of the described tipping elements the Greenland ice sheet, the Arctic sea-ice and the Atlantic thermohaline circulation (THC) have the greatest potential to affect Europe directly. Some models suggest that abrupt THC transitions could lead to regional cooling in Europe, though the popular idea of an “ice age” is incorrect. Greenhouse warming would very likely more than compensate for the reduced ocean heat transport for one or two centuries. This would result in reduced warming in Europe rather than cooling below present temperatures. There would be a number of other serious consequences of an abrupt ocean circulation change: additional sea level rise in the northern Atlantic region for example, and a major upheaval in northern Atlantic marine ecosystems.

As our paper shows, most experts judge the risk of passing the tipping point of the element Greenland ice sheet as higher. The risk for going beyond the tipping point of the Arctic sea-ice is judged as being at least as high, whereas this proposition is based on the pertinent literature and computer models. Greenland melting would raise sea level globally by meters. Loss of Arctic sea ice would transform the Arctic Ocean ecosystem and likely have a major effect on atmospheric circulation, which would affect the kind of weather and extremes we get in Europe. Both the loss of Greenland ice and Arctic sea-ice would increase freshwater input to the North Atlantic, which would weaken the THC. This could result in a chain reaction: vanishing Arctic sea ice leads to amplified high-latitude warming and accelerates loss of Greenland ice. The large freshwater input could then at some point shut off the Atlantic deep-water formation and disrupt the North Atlantic current which is part of the THC."

They disagree with the IPCC report late last year, they write:

"Given that the IPCC models significantly underestimate the observed rate of Arctic sea-ice decline (17), a summer ice-loss threshold, if not already passed, may be very close and a transition could occur well within this century."

We may be closer to a tipping point than we were told just a few months ago.