New paper finds another mechanism by which the Sun controls climate

A paper published today in Geophysical Research Letters finds that solar activity modulates the natural ocean oscillations the Pacific Decadal Oscillation [PDO] and the North Atlantic Oscillation [NAO]. These ocean oscillations, in turn, have large scale effects upon global climate. 

The authors find when the PDO is in phase with the 11 year sunspot cycle, the pattern of sea level pressures and surface temperatures shift in comparison to when they are out of phase. The authors also find the NAO is amplified when it is in phase with the sunspot cycle. 

These effects may represent another solar amplification mechanism by which tiny 0.1% changes in solar activity can be amplified to large scale effects upon climate.

Interactions between externally-forced climate signals from sunspot peaks and the internally-generated Pacific Decadal and North Atlantic Oscillations
Harry van Loon, Gerald A. Meehl

Abstract

When the PDO [Pacific Decadal Oscillation] is in phase with the 11 year sunspot cycle there are positive SLP [sea level pressure] anomalies in the Gulf of Alaska, nearly no anomalous zonal SLP gradient across the equatorial Pacific, and a mix of small positive and negative SST [sea surface temperature] anomalies there. When the two indices are out of phase, positive SLP anomalies extend farther south in the Gulf of Alaska and west into eastern Russia, with a strengthened anomalous zonal equatorial Pacific SLP gradient and larger magnitude and more extensive negative SST anomalies along the equatorial Pacific. In the North Atlantic, when the NAO [North Atlantic Oscillation] is in phase with the sunspot peaks, there is an intensified positive NAO SLP pattern. When the NAO is out of phase with the peaks, there is the opposite pattern (negative NAO). The relationships are physically consistent with previously identified processes and mechanisms, and point the way to further research.