The debate over whether greenhouse gases are primarily responsible for global warming can be a polarizing issue. Now there’s new data suggesting that weakening wind speeds, which are a naturally occurring phenomenon, are causing warming temperatures along the West Coast.

The study, conducted by researchers from the University of Washington and the National Oceanic and Atmospheric Administration, shows that ocean circulation changes caused by slower wind speeds were the primary cause of temperature rise between 1900 and 2012.

When coastal winds decrease, less evaporation occurs in the ocean. This, in turn, causes a shift in ocean currents that brings unusually warm water to the Pacific coast, raising the ocean temperature. Weak winds were shown to cause 80% of warming in the Pacific Northwest and 60% of temperature rise in Southern California.

Changing wind patterns are a well-documented occurrence. Systems like El Nino and the Pacific Decadal Oscillation can cause significant changes in ocean and land temperatures.

According to study leader James Johnstone, “Changing winds appear to explain a very large fraction of the warming from year to year, decade to decade and the long-term.”

This study discredits global warming as a major factor in West Coast warming trends, since the majority of temperature changes occurred prior to 1940. But many scientists are skeptical of pre-1950s data, since the methods of recording ocean and air temperature, as well as wind speed, were not as accurate as they are now.

Additionally, the study was only performed in one small area of the world. Its conclusions are not relevant for any area outside of the Pacific Northwest.

Nevertheless, the NOAA and University of Washington study shows that scientists must take regional changes into account when predicting future warming trends. While greenhouse gases are still a factor in global warming, they might not be the most significant factor in certain areas.