Expert judgements on the response of the Atlantic meridional overturning circulation to climate change

• Published in: Climatic change Vol. 82; no. 3-4; pp. 235 - 265
• Main Authors: ZICKFELD, Kirsten, LEVERMANN, Anders, MORGAN, M. Granger, KUHLBRODT, Till, RAHMSTORF, Stefan, KEITH, David W
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer 01.06.2007; Springer Nature B.V
• Subjects: Atlantic Meridional Overturning Circulation (AMOC); Carbon dioxide; Climate change; Climate models; Climatic evolution; Climatology. Bioclimatology. Climate change; Earth, ocean, space; Evolution; Exact sciences and technology; Experts; External geophysics; Global climate; Global temperatures; Greenhouse gases; Heat; Interviews; Laboratories; Marine; Mean temperatures; Meteorology; Observatories; Ocean circulation; Physics of the oceans; Precipitation; Precipitation distribution; Probability theory; Research programmes; Scientists; Sea level; Simulation; Temperature; Temperature rise; Thermohaline structure and circulation. Turbulence and diffusion; United States > US; Atlantic Ocean; AN, North Atlantic; Atlantic Ocean; Carbon dioxide; Impact study; ocean-atmosphere interaction; Scientific community; greenhouse gas; Dynamical climatology; Research worker; climate modification; Atmospheric temperature; global change; thermohaline circulation; prediction; Forcing; Opinion inquiry; ocean circulation
• ISSN: 0165-0009; 1573-1480
• DOI: 10.1007/s10584-007-9246-3

We present results from detailed interviews with 12 leading climate scientists about the possible effects of global climate change on the Atlantic Meridional Overturning Circulation (AMOC). The elicitation sought to examine the range of opinions within the climatic research community about the physical processes that determine the current strength of the AMOC, its future evolution in a changing climate and the consequences of potential AMOC changes. Experts assign different relative importance to physical processes which determine the present-day strength of the AMOC as well as to forcing factors which determine its future evolution under climate change. Many processes and factors deemed important are assessed as poorly known and insufficiently represented in state-of-the-art climate models. All experts anticipate a weakening of the AMOC under scenarios of increase of greenhouse gas concentrations. Two experts expect a permanent collapse of the AMOC as the most likely response under a 4xCO 2 scenario. Assuming a global mean temperature increase in the year 2100 of 4 K, eight experts assess the probability of triggering an AMOC collapse as significantly different from zero, three of them as larger than 40%. Elicited consequences of AMOC reduction include strong changes in temperature, precipitation distribution and sea level in the North Atlantic area. It is expected that an appropriately designed research program, with emphasis on long-term observations and coupled climate modeling, would contribute to substantially reduce uncertainty about the future evolution of the AMOC. [PUBLICATION ABSTRACT]