Should average global temperature increase by more than 4 degrees Celsius, one or several parts of the climate system could tip to a new state. Experts' estimates of the probability of tipping vary, and it also remains uncertain by how much global temperature will increase in the future.
But - as the authors report in the Proceedings of the National Academy of Sciences online early edition - these uncertainties do not imply that far-reaching events caused by global warming are unlikely.
An international team of researchers lead by Elmar Kriegler of the Potsdam Institute for Climate Impact Research (PIK) elicited the opinions of 52 climate scientists about the sensitivity of five so-called tipping elements. Tipping elements are parts of the climate system which, through human interference, can change quickly and irreversibly. In the current study the sensitivity of the following tipping elements is evaluated: Atlantic thermohaline circulation, El Niño phenomenon, Amazon rainforest, Greenland, and West Antarctic ice sheets.
43 experts estimated upper and lower bounds for the probability of those elements undergoing dramatic changes, given three different global warming scenarios: a warming by less than 2°C, by 2 - 4°C, or by an extreme of 4 - 8°C until 2200. "Strong global warming of more than 4°C by the year 2200 so far does appear to be a clear possibility", Kriegler says.
The analysis of the survey is now published in the online version of the US American "Proceedings of the National Academy of Sciences". If temperatures were to increase by 2 - 4°C then - so the scientists estimate - at least one element will tip with a one in six chance. If global temperatures were to increase even further then this probability increases to more than one in two (56%). In such a warming scenario the majority of respondents consider the probability of a complete melting of the Greenland ice sheet and a large-scale die-back of the Amazon rainforest to be particularly high. "The results show that the estimated probabilities increase strongly parallel to the progressive scenarios of future warming" Kriegler summarises the expert survey.
The authors write that expert elicitations have occasionally been criticised for not contributing new scientific information as long as they are not backed by new data, modelling or theories. However, in the context of risk analysis such surveys have proven to be a useful tool to summarise expert knowledge for decision makers. "We do not prescribe society specific climate policy measures," says 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."
Reorganization of the Atlantic Thermohaline Circulation: Most of the experts believe that the ocean circulation will remain stable under small future warming. However, if global temperatures were to rise by more than 4°C experts see a significant increase in the probability of a collapse of the existing system of Atlantic circulation.
Increased occurrence of the El-Niño phenomenon and large-scale die-off of the Amazon rainforest: Even if intense warming should occur some experts do not expect any change of the El-Niño phenomenon. Others estimate that El-Niño will become more frequent. The continued existence of the Amazon rainforest depends on these potential changes, because the El-Niño phenomenon causes drought in the Amazon region. In case of increased recurrences of El-Niño models indicate that large parts of the rainforest will die off. Most experts assume a one in two chance for a large-scale die-back of the rainforest in case of warming by more than 4°C.
Complete melting of the Greenland Ice Sheet: Even for a warming by less than 2°C some of the respondents see the risk of a complete melting of the Greenland ice sheet. For a strong increase of global temperature by more than 4°C almost all experts expect a melting of the ice sheet with a high probability of more than one in two.
Disintegration of the West Antarctic ice sheet: There are significant uncertainties in our knowledge about the response of the ice sheet to further warming. Therefore, experts differ in their estimates of the probability of its disintegration. Higher probability estimates may have been motivated by recent findings of acceleration of inland glaciers following the disintegration of ice shelfs on the West Antarctic peninsula.
Article: Elmar Kriegler, Jim W. Hall, Hermann Held, Richard Dawson, and Hans Joachim Schellnhuber (2009). Imprecise probability assessment of tipping points in the climate system. Proceedings of the National Academy of Sciences, Online Early EditionFor further information please contact the PIK press office:
Uta Pohlmann | idw
NASA finds newly formed tropical storm lan over open waters
17.10.2017 | NASA/Goddard Space Flight Center
The melting ice makes the sea around Greenland less saline
16.10.2017 | Aarhus University
University of Maryland researchers contribute to historic detection of gravitational waves and light created by event
On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...
Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.
Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....
Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).
When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...
Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.
How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...
Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.
It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...
17.10.2017 | Event News
10.10.2017 | Event News
10.10.2017 | Event News
17.10.2017 | Life Sciences
17.10.2017 | Life Sciences
17.10.2017 | Earth Sciences