Natural climate variations, which tend to involve localized changes in sea surface temperature, may have a larger effect on hurricane activity than the more uniform patterns of global warming, a new study suggests.

Warmer oceans due to global warming are generally assumed to provide a more favorable environment for hurricane development and intensification, but according to the study from the journal Nature, other factors such as atmospheric temperature and moisture come into play, which in my opinion is fairly obvious to a meteorologist. Anyway, Dr. Gabriel Vecchi from NOAA's Geophysical Fluid Dynamics Laboratory (GFDL) and Brian J. Soden from the University of Miami Rosenstiel School of Marine & Atmospheric Science went further and explored the relationship between changes in sea surface temperature and tropical cyclone "potential intensity", which is a measure that provides an upper limit on cyclone (hurricane) intensity.

Excerpts taken from the Science Daily article.........

They found that warmer oceans do not alone produce a more favorable environment for storms because the effect of remote warming can counter, and sometimes overwhelm, the effect of local surface warming. "Warming near the storm acts to increase the potential intensity of hurricanes, whereas warming away from the storms acts to decrease their potential intensity," Vecchi said.

Their study found that long-term changes in potential intensity are more closely related to the regional pattern of warming than to local ocean temperature change. Regions that warm more than the tropical average are characterized by increased potential intensity, and vice versa. "A surprising result is that the current potential intensity for Atlantic hurricanes is about average, despite the record high temperatures of the Atlantic Ocean over the past decade." Soden said. "This is due to the compensating warmth in other ocean basins." "If the Atlantic warms more slowly than the rest of the tropical oceans, we would expect a decrease in the upper limit on hurricane intensity," Vecchi added.

A group of U.S. scientists studying updated climate models have determined that previous projections had underestimated the process now driving ice loss and indicate that the northern polar waters could be ice-free during the summers by 2013.

Actually, according to professor Wieslaw Maslowski, a researcher from the Naval Postgraduate School in Monterey, California, the 2013 projection does not even take into account the last two Arctic sea ice minima seasons of 2005 and 2007, since the study used data sets from 1979-2004 to make their future projections. "So given that fact, you can argue that may be our projection of 2013 is already too conservative," said Maslowski.

Maslowski believes other, more conservative model projections seriously underestimated the amount of heat delivered to the sea ice by oceanic advection, such as how warm water is moving into the Arctic basin from the Pacific and Atlantic Oceans.

According to the study from the BBC article, it has become apparent in recent years that the real, observed rate of summer ice melting is now starting to run well ahead of the models.

Arctic ice expert, professor Peter Wadhams from Cambridge University, UK has used sonar data collected by submarines to show that the volume loss is outstripping even area withdrawal, which agrees with Maslowski's work. "The ice is thinning faster than it is shrinking; and some modellers have been assuming the ice was a rather thick slab," said Wadhams. "The implication is that this is not a cycle, not just a fluctuation. The loss this year will precondition the ice for the same thing to happen again next year, only worse."