Hurricanes and Global Warming: Expectations versus Observations

Chris Landsea
National Hurricane Center


Climate variability and any resulting change in the characteristics of tropical cyclones (tropical storms, subtropical storms, and hurricanes) have become topics of great interest and research within the past four years. Some recent scientific articles have reported a large increase in tropical cyclone energy, numbers, and windspeeds in many basins during the last few decades in association with warmer sea surface temperatures. These increases in tropical cyclone activity have been linked to man-made greenhouse gas changes.

It is not disputed (by this speaker) that anthropogenic forcing has been the cause of at least a substantial portion of the observed warming during the 20th Century. It is likely that some increase in tropical cyclone peak windspeed has occurred and will continue to occur if the climate continues to warm. However, whether greenhouse gas warming is related in increases in tropical cyclone activity is NOT the most relevant question. One needs to address instead: What is the SENSITIVITY of tropical cyclone intensity, frequency and overall activity to greenhouse gas forcing? Is it indeed large today, or is it likely to be a small factor even several decades from now?

These questions as well as an attempt to reconcile theoretial/numerical modeling studies with some recent (well publicized) observational papers will be addressed in the talk. Finally, how these greenhouse gas warming changes compare versus other alterations in our society (increased population and infrastructure in vulnerable coastal locations) will also be discussed.