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
Stagnation in the South Pacific Explains Natural CO2 Fluctuations
23.02.2018 | Carl von Ossietzky-Universität Oldenburg
First evidence of surprising ocean warming around Galápagos corals
22.02.2018 | University of Arizona
A newly developed laser technology has enabled physicists in the Laboratory for Attosecond Physics (jointly run by LMU Munich and the Max Planck Institute of Quantum Optics) to generate attosecond bursts of high-energy photons of unprecedented intensity. This has made it possible to observe the interaction of multiple photons in a single such pulse with electrons in the inner orbital shell of an atom.
In order to observe the ultrafast electron motion in the inner shells of atoms with short light pulses, the pulses must not only be ultrashort, but very...
A group of researchers led by Andrea Cavalleri at the Max Planck Institute for Structure and Dynamics of Matter (MPSD) in Hamburg has demonstrated a new method enabling precise measurements of the interatomic forces that hold crystalline solids together. The paper Probing the Interatomic Potential of Solids by Strong-Field Nonlinear Phononics, published online in Nature, explains how a terahertz-frequency laser pulse can drive very large deformations of the crystal.
By measuring the highly unusual atomic trajectories under extreme electromagnetic transients, the MPSD group could reconstruct how rigid the atomic bonds are...
Quantum computers may one day solve algorithmic problems which even the biggest supercomputers today can’t manage. But how do you test a quantum computer to...
For the first time, a team of researchers at the Max-Planck Institute (MPI) for Polymer Research in Mainz, Germany, has succeeded in making an integrated circuit (IC) from just a monolayer of a semiconducting polymer via a bottom-up, self-assembly approach.
In the self-assembly process, the semiconducting polymer arranges itself into an ordered monolayer in a transistor. The transistors are binary switches used...
Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale
Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...
15.02.2018 | Event News
13.02.2018 | Event News
12.02.2018 | Event News
23.02.2018 | Physics and Astronomy
23.02.2018 | Health and Medicine
23.02.2018 | Physics and Astronomy