J8.4 Hurricanes and Global Warming: Expectations versus Observations (2008

J8.4

Hurricanes and Global Warming: Expectations versus Observations

Christopher W. Landsea, NOAA/NWS/TPC/NHC, Miami, FL

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

three

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.