Earth's climate veers between warm and cool roughly every 1,500 years. Many scientists have thought that sunspots choreograph these fluctuations, but new research puts the spotlight on the moon.
A few years ago geochemist Charles D. Keeling and geophysicist Timothy P. Whorf, both of the Scripps Institution of Oceanography in La Jolla, Calif., suggested that Earth's climate doesn't swing with sunspot rhythms but instead syncopates to the beat of the tides.
When tides are higher than usual, the scientists say, they bring colder water to the surface from deep in the ocean and lead to an overall Earth cooling. In a report in the April 11 Proceedings of the National Academy of Sciences, the researchers propose that the tides may sometimes be strong enough to tug Earth into an ice age.