A new study is challenging the assumption that increasing greenhouse gases is the main reason for increased temperatures along the west coast of North America over the past 100 years.
The study, published in the Proceedings of the National Academy of Sciences (PNAS), points to natural changes in wind.
Study Points to Wind
According to the study, the average coastal temperature increase of 1 degree Celsius over the past century along the West Coast could have come from changes in winds over the eastern Pacific Ocean.
The conclusion doesn’t seem far-fetched. Wind patterns, such as El Nino, have been known to impact temperatures over a long stretch.
How can wind effect temperatures over a large area? Weak coastal winds lead to less evaporation from the sea surface. Think running on a completely calm day versus a windy one. Your sweat evaporates more on the windy day. Same concept here. Except the weakening winds leads to low pressure that changes ocean currents and leads to a slow, steady rise in temperatures over time.
The study found the Pacific Northwest saw the greatest impact from wind changes with it accounting for more than 80% of the warming since 1900. Weaker winds were responsible for 60% of the warming in Southern California according to the study
“Changing winds appear to explain a very large fraction of the warming from year to year, decade to decade and the long-term,” study leader James Johnstone told the LA Times.
The West Coast Isn’t the World
Today’s study focused on trends at a regional level. Wind changes on a global level were not looked at. A look at temperature changes and their causes over a small area, globally speaking, doesn’t disprove global warming. It does show more science needs to be conducted on how temperatures are affected by changes, natural or otherwise, on a regional level.
For example, August was the hottest month ever according to NOAA, yet the eastern portion of the United States saw below average temperatures.