In our paper
Rial, J., R.A. Pielke Sr., M. Beniston, M. Claussen, J. Canadell, P. Cox, H. Held, N. de Noblet-Ducoudre, R. Prinn, J. Reynolds, and J.D. Salas, 2004: Nonlinearities, feedbacks and critical thresholds within the Earth’s climate system. Climatic Change, 65, 11-38,
we concluded that
“The Earth’s climate system is highly nonlinear: inputs and outputs are not proportional,
change is often episodic and abrupt, rather than slow and gradual, and multiple equilibria are the
norm.”
A new Science perspective article reinforces this conclusion. The article is
Flückiger, J., 2008: Did you say “Fast”? Science, 321, 651-651. (subscription required)
Extracts from the paper read
“…… some might be stunned by how quickly climate can change. On page 680 of this issue, Steffensen et al. … zoom in on three climatic shifts recorded in the NGRIP ice core from central Greenland (see the photo) (2) and show that the atmospheric circulation at mid to high northern latitudes changed within just 1 to 3 years.”
“The surprising result is that the deuterium excess shifts within 1 to 3 years. The authors interpret the deuterium excess data as a reorganization of the atmospheric circulation in mid to high northern latitudes, leading to a spatial shift in the source region and, therefore, the source temperature of the precipitation….”
“Generally, abrupt climatic events such as those studied by Steffensen et al. are associated with changes in the strength of the Atlantic meridional overturning circulation (3). Steffensen et al. hypothesize that additionally, the Northern Hemisphere atmospheric circulation had a very sensitive threshold, which led to the observed fast reorganization. The slower changes found in Greenland temperature and dust might be dominated by the effects of the slower changing ocean circulation and its far-field effects.”
“The data reported by Steffensen et al. underscore the fact that the atmospheric circulation may shift from one state to another within just 1 year. With ongoing global warming, the climate system might therefore hold some surprises.”
Only the last sentence in the above paragraph fails to accurately summarize the significance of the Steffensen et al Science article which is that
Both natural and the range of diverse human climate forcings (e.g. see) can result in atmospheric circulation changes! The climate system has “surprises” regardless if global warming occurs. The failure to recognize that
“The Earth’s climate system is highly nonlinear: inputs and outputs are not proportional, change is often episodic and abrupt, rather than slow and gradual, and multiple equilibria are the norm”
and that many forcings other than “global warming” can produce this nonlinear response in the climate system is a significant oversight in the otherwise quite valuable summary by Flückiger of the Steffensen et al Science article.