Another report indicates natural processes play a role.
North Atlantic warming study cites 50-year natural cycle
CanWest News Service
Saturday, January 05, 2008
The authors of a new paper published this week argue that warmer water in the North Atlantic Ocean, often cited as being caused by climate change and a trigger of more severe storms, may have partly natural causes.
Researchers from North Carolina's Duke University say an analysis of available records shows an uneven warming of the North Atlantic Ocean's surface waters in a 50-year period between 1950 and 2000.
Susan Lozier, a professor of physical oceanography and a lead author on the paper, believes that it is premature to "conclusively attribute these regional patterns of heat gain to greenhouse warming."
The research appeared Thursday in Science Express, the online edition of the journal Science.
Although the surface waters warmed over the 50-year period, the subpolar regions cooled while the subtropical and tropical waters of the North Atlantic warmed. The pattern is attributed to the North Atlantic Oscillation (NAO), a natural, cyclical wind circulation that has a strong impact on the underlying ocean.
"So contrary to some people's expectations, as our climate evolves we might expect everything to get warmer, but what we found instead is we had a very sharp contrast between these two regions," Lozier said.
In fact, the researchers say that large-scale, decadal changes "associated with the NAO are primarily responsible for the heat ocean content changes in the North Atlantic over the past 50 years."
Lozier said she hoped the research wouldn't be used as a "referendum on whether there is or isn't greenhouse warming." Rather, she said the more "interesting story" is that both natural variability and human change are causing warming in the waters.