Modeling Abrupt Climate Change

The Gulf Stream and North Atlantic Climate. Assessed the relative importance of seasonal storage and release of heat by the ocean, movement of heat by ocean currents, and movement of heat by the atmosphere for determining the climates around the North Atlantic Ocean. Emphasized the role of atmospheric flow, rather than ocean currents, in making Europe's winter warm and Eastern North America cold. This allows a more sure assessment of the climate impacts of a possible future slowdown of the thermohaline circulation.
Changing ENSO. Changes in ENSO over the last century and a half have occurred abruptly and caused global climate impacts. By many measures the 1976/77 transition was an abrupt climate change that had serious consequences for climate around the world. We have demonstrated that these decadal changes in ENSO state are predictable, to a useful degree, years in advance. We predict that the 1997/98 El Nino ended the post 1976 warm state of the tropical Pacific ushering in a cold state that will last a decade or more from now.
Droughts. We have related decadal changes of ENSO to droughts and wet conditions over North America. Significant droughts in the Great Plains in the 1930s (the Dust Bowl) and mid Nineteenth Century, and in the Southwest in the 1950s, have been related by modeling to persistent La Nina conditions. Similarly the rapid onset of drought in the West since 1998 is related to the end of the post 1976 warm state of the tropical Pacific and can be expected to last.