1. Forecasters at the National Hurricane Center rely on about five to 10 models for any particular forecast, Rappaport said, with one known as the "GFDL" as the lead model.

2. "This very long–term increase in temperature may seem small," said Thomas Knutson, lead author and a senior research meteorologist at the NOAA Geophysical Fluid Dynamics Laboratory (GFDL) in New Jersey, "but is comparable in magnitude to shorter–time–scale, multi–decadal changes that many scientists now believe contribute strongly to an increase in hurricane activity in the Atlantic." The challenge, Knutson said, "is to understand the relative roles of anthropogenic [human–generated] and natural factors in producing these temperature changes âЂ« and this study is a step in that direction âЂ« and then to determine whether and how these long–term changes in temperature could be affecting Atlantic hurricane activity." NEW CLIMATE MODEL The climate model simulations are based on a new atmosphere–ocean model developed over several years at GFDL.