Much of climate change work has focussed on changes in the mean of some variable, such as the mean temperature of the Earth. The mean, however, is not the only quantity of relevance, and we can also ask how might the fluctuations in the variables change.   We have been working on a project looking at impacts of climate change on extreme events from a dynamical systems perspective.  In some recent work, we have found some startling results.

In looking at the response of simple nonlinear systems to very simple forcing (constant forcing on the Lorenz equations, in this case) we have found great sensitivity of extreme persistent events to small forcing.  Even while the means change only by a small amount, the frequency of occurrence of extreme events changes by huge factors; this is a result of changes in the stability of different regimes of the attractor. If this effect carries over to the real climate system, a question we are continuing to pursue, it has huge implications for society, in terms of potential changes in the frequencies of floods, droughts, and other climate events with global change.

A paper describes this work further:

Samar Khatiwala, Bruce E. Shaw, and Mark A. Cane,
`Enhanced sensitivity of extreme events to weak forcing in a dynamical system:
Implications for climate change',
Geophysical Research Letters, 28, 2633, 2001.