LA Times: West Coast warming linked to naturally occurring changes – Published in PNAS
'Naturally occurring changes in winds, not human-caused climate change, are responsible for most of the warming on land and in the sea along the West Coast of North America over the last century, a study has found. The analysis challenges assumptions that the buildup of greenhouse gases in the atmosphere has been a significant driver of the increase in temperatures observed over many decades in the ocean and along the coastline from Alaska to California.'
'If global warming had been the most powerful influence on land and sea temperatures, those temperatures would have been different, the study's authors said. Most of the warming in the region occurred before 1940, when greenhouse gas concentrations were lower and winds were weaker, the study found. In contrast, winds have strengthened since 1980 and coastal ocean cooled, even as the rise in greenhouse gases has accelerated.'
‘Changes in ocean circulation as a result of weaker winds were the main cause of about 1 degree Fahrenheit of warming in the northeast Pacific Ocean and nearby coastal land between 1900 and 2012, according to the analysis of ocean and air temperatures over that time. The study, conducted by researchers from the National Oceanic and Atmospheric Administration and the University of Washington, was published Monday by the Proceedings of the National Academy of Sciences.’
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Kevin Trenberth, a climate scientist at the National Center for Atmospheric Research in Boulder, Colo., who was not involved in the study, said its conclusions about long-term trends were probably overstated because the quality of data from the early 20th century was poor and unreliable. The results may also reflect the fact that the northeast Pacific is an area of the globe where past studies have shown the “signal” of climate change is low relative to the “noise” of natural variability.
“There is no doubt that regionally, the changes in temperature are dominated by changes in the atmospheric circulation that likely have little or nothing to do with climate change,” Trenberth said. But, he added, “this does not call into question the concept of global warming.”
