FACTBOX: Debate over global warming link to hurricanes

(Reuters) - Many climate scientists believe there is a link between global warming and hurricane strength, but the debate is not settled.

As Mexico and Central America battle the impact of two top-strength Category 5 hurricanes in less than a month, here is some background on the debate.

* Factors that influence hurricanes include warm ocean water temperatures in the tropical Atlantic Ocean and Caribbean Sea, moisture in the atmosphere, light winds at high altitude and existing weather disturbances, according to the U.S. National Oceanic & Atmospheric Administration.

* Recent climate studies suggest that a warming of the tropical Atlantic and Caribbean is due to the increase in greenhouse gas emissions, and that these warmer waters fuel development and intensification of hurricanes, NOAA says.

* Warmer sea surface temperatures and moister air provide more energy for showers and thunderstorms that feed hurricanes, pushing more of them into the extreme category, according to computer models cited by the nongovernmental National Center for Atmospheric Research.

* Hurricanes are expected to be more intense as sea surface temperatures rise, but there is significant uncertainty about how other influences on hurricane strength will change, the American Meteorological Society says.

* More strong hurricanes have hit the U.S. mainland since 1995 than in the 25 years before that. There were also periods with relatively more comparably strong hurricanes earlier in the 20th century.