North Atlantic warming not due to climate change
North Atlantic warming not due to climate change
Rhett A. Butler, mongabay.com
January 3, 2008
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While overall temperature in the North Atlantic Ocean has risen over the past fifty years, it has not been consistent across all areas with subpolar regions cooling as subtropical and tropical waters warmed, reports a new study published in the journal Science.
The pattern can be explained by the influence of a natural and cyclical wind circulation pattern called the North Atlantic Oscillation, rather than greenhouse gas emissions, say the authors.
“The winds have a tremendous impact on the underlying ocean,” said Susan Lozier, a professor of physical oceanography at Duke University and leader author of the study. “The take-home message is that the NAO produces strong natural variability.”
 Change in ocean heat content (1020J; red represents a gain in heat for the later period) between the twenty-year periods 1980-2000 and 1950-1970 diagnosed from (a) historical data integrated over the water column. Courtesy of Science |
“The simplistic view of global warming is that everything forward in time will warm uniformly. But this very strong natural variability is superimposed on human-caused warming. So researchers will need to unravel that natural variability to get at the part humans are responsible for.”
Nevertheless the researchers say the results don’t undermine data showing that warming is occurring in other oceans, but simply that observed warming in the North Atlantic is so far driven by natural shifts rather than climate change.
“In the North Atlantic, any anthropogenic (human-caused) warming would presently be masked by such strong natural variability,” they wrote.
CITATION: Lozier, M.S. (2007). he Spatial Pattern and Mechanisms of Heat Content Change in the North Atlantic. Science January 4, 2008