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Survey: 4 ºC Temperature Rise Likely To Trigger At Least One Tipping Element

A survey of 52 climate scientists, conducted by the Potsdam Institute for Climate Impact Research (PIK), on the likelihood of triggering any of five “tipping elements”—massive components of the climate system which could be flipped to a new equilibrium in a relatively short amount of time—has yielded results which included 43 responses that estimated upper and lower bounds of the probability of such events.

The tipping elements considered in the survey are:

  • Reorganization of the Atlantic thermohaline circulation;
  • El Niño-Southern Oscillation (ENSO) phenomenon;
  • Dieback of the Amazon rainforest (which is related to El Niño);
  • Collapse of the Greenland ice sheet; and
  • Collapse of the West Antarctic ice sheets.

As “strong global warming of more than 4 °C by the year 2200 so far does appear to be a clear possibility,” according to lead author Elmar Kriegler, respondents to the survey were asked to consider three warming scenarios through the year 2200: less than 2 ºC; 2-4 ºC; and 4-8 ºC above 2000 levels. On average, warming of 2-4 ºC was seen to have a one in six possibility of triggering at least one tipping element, rising to a more than one in two possibility (56%) if warming were to increase further.

Noting that “expert elicitations” are sometimes criticized for presenting information that is not backed by new data, the authors nevertheless assert that expert surveys can be useful tools in the context of risk analysis. “We do not prescribe society-specific climate policy measures,” explained Hans Joachim Schellnhuber, director of PIK and coauthor of the article. “But the results of the survey provide further evidence for the need of ambitious climate protection in order to minimize the risks of far-reaching consequences for our entire planet.

Tipping Elements: Survey Results

Reorganization of the Atlantic thermohaline circulation: Although most experts surveyed believe that ocean circulation will remain stable under 2 ºC or less future warming above 2000 levels, they see a significant increase in the probability of a collapse of the existing system of Atlantic circulation if global temperatures rise by more than 4 °C.

Increased occurrence of the El-Niño phenomenon and large-scale die-off of the Amazon rainforest: Opinion varied with regard to El Niño, with some experts expecting no change in the phenomenon, and others estimating that El-Niño will become more frequent. However, models indicate that large parts of the Amazon rainforest will be killed by drought related to El Niño if warming persists. Most experts stated a one in two chance of a large-scale dieback of the rainforest in case of warming by more than 4 °C.

Complete melting of the Greenland Ice Sheet (GIS): Almost all respondents expect a melting of the ice sheet at 4 ºC or more of warming, with a high probability of more than one in two.

Disintegration of the West Antarctic ice sheet (WAIS): No one opinion trend emerged with regard to WAIS disintegration. Significant uncertainties remain in scientific understanding of the response of the ice sheet to further warming. Therefore, experts differ in their estimates of the probability of its disintegration. Recent estimates of higher probabilities may have been influenced by the acceleration of inland glaciers following the disintegration of ice shelfs on the West Antarctic peninsula.

The survey and its methodology have been published online in the Proceedings of the National Academy of Sciences of the United States (PNAS).

—Jack Rosebro


  • Elmar Kriegler et al. (2009) Imprecise probability assessment of tipping points in the climate system. PNAS 10.1073/pnas.0809117106


The Goracle


Complete melting of the Greenland Ice Sheet (GIS)

LOL!!! So... Greenland may become Greenland... AGAIN. You alarmists are so silly! Although you do make a LOT of money off of your claims of doom. Silly me, not joining in on the profit taking!



You can laugh all you want Goracle. It will not stop the impending legislation. So suck it up.

The Goracle

It will not stop the impending legislation.

The best part about legislation is that congress will never inconvenience themselves. So, there will be a slew of loopholes that we will be able to use to get around any new regulations. It's all about the MONEY!!!

Will S

Read this map and see where you'd like to live when temps reach +4C.


"Noting that “expert elicitations” (sic)are sometimes criticized for presenting information that is not backed by new data..."

You mean this is just personal conjecture published by the creative writing department?? These sims are slipping.

”Pairs of tipping events A, B are connected with a directed arrow A 3 B if (i) at least 4 experts judged that some effect of triggering A on the probability of triggering B exists and (ii) they outnumbered the experts who saw no effect of A on B.”



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