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 preprint 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', submitted, 2000.