It’s Relative: Contrasting Hurricane Theories Heat Up

Recent hurricane history provides diverging interpretations on future of hurricane activity

cane hypothesis
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Virginia Key, Fla. (October 31, 2008) — In a paper published in the journal Science on October 31, scientists Gabriel A. Vecchi of NOAA’s Geophysical Fluid Dynamics Laboratory, Kyle L. Swanson of the University of Wisconsin - Milwaukee Atmospheric Sciences Group and Brian J. Soden from the University of Miami’s Rosenstiel School of Marine and Atmospheric Science teamed up to study hurricane data observed over more than 50 years. The study explores the relationship between sea surface temperature (SST) and seasonal hurricane activity, and show how differing interpretations of the observational record can imply vastly different futures for Atlantic hurricane activity due to global warming.  The two interpretations arise from assumptions of whether it is the local SST in the Atlantic in isolation, or whether it is the SST in the Atlantic ‘relative’ to the rest of the tropics, that drives variations in Atlantic hurricane activity.

If one assumes the former (the local SST hypothesis), then by 2100, the lower bound on Atlantic hurricane activity is comparable to that of 2005, when four major hurricanes struck the continental United States, causing more than $100 billion in damage. The upper bound exceeds 2005 levels by more than a factor of two. However, if one assumes the latter (the relative SST hypothesis), then the future is similar to the recent past, with periods of higher and lower hurricane activity relative to present-day conditions due to natural climate variability, but with little long-term trend.

The statistical relationship between either interpretation of the SST/hurricane activity link is ambiguous over the period 1946-2007 (they are statistically indistinguishable, though both are significant), but they imply fundamentally different projections for the future and interpretations of the past. The team further argues that the consistency between theory, numerical models, and historical observations offers compelling evidence that the ‘relative’ SST hypothesis is more accurate and provides a better framework for projections of future changes in hurricane activity.

About the Rosenstiel School
Founded in the 1940's, the University of Miami's Rosenstiel School of Marine & Atmospheric Science has grown into one of the world's premier marine and atmospheric research institutions. Offering dynamic interdisciplinary academics, the Rosenstiel School is dedicated to helping communities to better understand the planet, participating in the establishment of environmental policies, and aiding in the improvement of society and quality of life.  For more information, please visit

About University of Wisconsin — Milwaukee
The Atmospheric Sciences Group at the University of Wisconsin - Milwaukee engages in a wide range of research. Specializations include climate variability, cloud physics and numerical modeling, atmospheric dynamics, synoptic meteorology, air pollution meteorology, and nonlinear dynamics and chaos. The group benefits greatly from the fact that it is embedded in the Department of Mathematical Sciences, which promotes fruitful collaboration with mathematicians.

About NOAA Geophysical Fluid Dynamics Laboratory
The goal of NOAA’s GFDL research is to understand and predict the Earth's climate and weather, including the impact of human activities.  GFDL conducts leading edge research on many topics including weather and hurricane forecasts, El Ni—o prediction, stratospheric ozone depletion, and climate change. For more information, please visit

Media Contacts:

Barbra Gonzalez
UM Rosenstiel School of Marine and Atmospheric Science
Marie Guma-Diaz
UM Media Relations Office