cc: Nick McCave , Bob Marsh , John Lawton date: Tue, 10 Dec 2002 10:10:10 +0000 from: Jochem Marotzke subject: RS Mtg., Abrupt Climate Change to: Bob Dickson , Alan Kemp , Richard Wood , Richard Alley , Eli Tziperman , Harry Elderfield , Meric Srokosz , Brian Hoskins , Andrey Ganopolski , Hugh Jenkyns , Mike Hulme , Christian Koerner , Charles Perrings Dear All: Thank you again for agreeing to speak at our Royal Society Discussion Meeting on 4/5 February next year. With some of you perhaps having started to think about your presentation and accompanying paper, I thought a few general thoughts about the science of Abrupt Climate Change might be helpful in the discussion. Invariably, the question arises what is meant by "Abrupt" in this context, and the committee, chaired by Richard Alley, that wrote the "Abrupt Climate Change: Inevitable Surprises" report for the U.S. National Research Council struggled with this more than with any other issue during the writing of the report. The difficulty was, should we even try to define it? Or is all we can say that we recognise it when we see it? In the end, we did tackle the "definition thing", and produced what I still feel is a good answer. In a paper that Richard was invited to submit to Science, we summarised it as: "Technically, an abrupt climate change occurs when the climate system is forced to cross some threshold, triggering a transition to a new state at a rate determined by the climate system itself and faster than the cause" (NRC, 2002, p. 14). The cause may be chaotic and thus undetectably small. For human concerns, attention is especially focused on persistent changes that affect subcontinental or larger regions, and for which ecosystems and economies are unprepared or are incapable of adapting. NRC, 2002. Abrupt Climate Change: Inevitable Surprises. National Academy Press, 230pp. See online version, http://www.nap.edu/catalog/10136.html for the more comprehensive definition. I don't wish to be prescriptive, but you may find this definition useful as a common reference point for our discussion. Best regards, Jochem Marotzke -- ================================================================ Professor Jochem Marotzke, Jochem.Marotzke@soc.soton.ac.uk School of Ocean and Earth Science, SOC, Room 566/11 University of Southampton, Tel: + 44-(0)23-80593755 Southampton Oceanography Centre, Fax: + 44-(0)23-80593059 European Way Southampton SO14 3ZH, United Kingdom http://www.soes.soton.ac.uk/research/groups/ocean_climate ================================================================