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."
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."
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