Debunking the Solar-Cycle/North Atlantic Winter Weather Connection

Feb 20 2019 | By By Holly Evarts, Originally published by Columbia Engineering

A new Nature Geoscience study from Applied Physics and Applied Mathematics (APAM) and Lamont Doherty researchers has upended a commonly accepted theory that variations in the energy emitted by the sun affect weather patterns in the North Atlantic and the likelihood of storms and floods over Europe. The North Atlantic Oscillation (NAO) is considered a key driver of winter weather patterns over the northern hemisphere. A positive NAO is linked with more windstorms, and mild and wet winters in Europe. A negative NAO indicates snowy and cold winters in Europe.

In recent years, published research has claimed the existence of a correlation between the NAO and the 11-year solar cycle, a periodic change in the sun’s activity. That claim has held that the connection between the NAO and the solar cycle is strong enough to inform predictions of the NAO as much as a decade in advance, which would in turn, enable scientists to predict winter weather patterns as many as ten years in advance.

APAM research scientist Gabriel Chiodo and PhD student Jessica Oehrlein, together with Professor Lorenzo Polvani (also a professor of Earth and Environmental Sciences) showed in the new study that there is no robust connection between the solar cycle and the NAO. Their paper essentially debunks what was considered a “demonstrated link” between the 11-year sun cycle and winter weather over the northern hemisphere and found that it is, for the most part, a coincidental alignment. Using sophisticated computer modeling and extended observations, they demonstrated that before 1960 evidence of any correlation simply vanishes.

The implications of these new findings are substantial both for Europe and for science. The older correlation claim, if substantiated, would have meant great advantages to societies in the northern hemisphere, giving enough warning of periods of intense storms and flooding to inform community planning efforts. But this new finding—“Insignificant influence of the 11-year solar cycle on the North Atlantic Oscillation”—will be important for climate research into the future, as it implies that the causes for decadal weather changes over Europe lies elsewhere, not in the solar variations.