A new study makes the case that human activity played very little role in the warming of the northeast Pacific Ocean over the past century or so.
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.
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.
Natural, wind-driven climate patterns in the Pacific Ocean, such as El Niño and the Pacific Decadal Oscillation, are already known to exert a powerful influence on sea and land temperatures over years and even decades.
This latest research shows that similar changes in atmospheric and ocean circulation can drive trends that last a century or longer, overshadowing the effects of human-generated increase in greenhouse gases, the study’s authors said.