J Michael T Thompson (1, 2) and Jan Sieber (3)
(1) Dept of Applied Mathematics & Theoretical Physics, Cambridge University,
Centre for Mathematical Sciences, Wilberforce Road, Cambridge, CB3 0WA, UK.
(2) School of Engineering (Sixth Century Professor), Aberdeen University
(3) Dept of Mathematics, University of Portsmouth,
Portsmouth, PO1 3HF, UK.
There is currently much interest in examining climatic tipping points, to see if it is feasible to predict them in advance. Using techniques from bifurcation theory, recent work looks for a slowing down of the intrinsic transient responses, which is predicted to occur before an instability is encountered. This is done, for example, by determining the short-term autocorrelation coefficient ARC(1) in a sliding window of the time series: this stability coefficient should increase to unity at tipping. Such studies have been made both on climatic computer models and on real paleoclimate data preceding ancient tipping events. The latter employ re-constituted time-series provided by ice cores, sediments, etc, and seek to establish whether the actual tipping could have been accurately predicted in advance. One such example is the end of the Younger Dryas event, about 11,500 years ago, when the Arctic warmed by 7℃ in 50 years. A second gives an excellent prediction for the end of 'greenhouse' Earth about 34 million years ago when the climate tipped from a tropical state into an icehouse state, using data from tropical Pacific sediment cores. This prediction science is very young, but some encouraging results are already being obtained. Future analyses, relevant to geo-engineering, will clearly need to embrace both real data from improved monitoring instruments, and simulation data generated from increasingly sophisticated predictive models.
Prepared as an extra Chapter for a book to be published by Cambridge University Press entitled Geo-Engineering Climate Change, edited by Brian Launder and Michael Thompson, to appear in 2009.
The book is based on the Theme Issue of Phil. Trans. R. Soc., A, Vol 366, No 1882, 2008 entitled Geoscale Engineering to avert Dangerous Climate Change (eds. B. Launder & J.M.T. Thompson).
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