Solar cycle signals in sea level pressure and sea surface temperature

Abstract. We identify solar cycle signals in 155 years of global sea level pressure (SLP) and sea surface temperature (SST) data using a multiple linear regression approach. In SLP we find in the North Pacific a statistically significant weakening of the Aleutian Low and a northward shift of the Hawaiian High in response to higher solar activity, confirming the results of previous authors using different techniques. We also find a weak but broad reduction in pressure across the equatorial Pacific. In SST we identify a weak El Niño-like pattern in the tropics for the 155 year period, unlike the strong La Niña-like signal found recently by some other authors. We show that the latter have been influenced by the technique of compositing data from peak years of the sunspot cycle because these years have often coincided with the negative phase of the ENSO cycle. Furthermore, the date of peak annual sunspot number (SSN) generally falls a year or more in advance of the broader maximum of the 11-year solar cycle so that analyses which incorporate data from all years represent more coherently the difference between periods of high and low solar activity on these timescales. We also find that studies of the solar signal in SST over the second half of the 20th century may alias as ENSO signal if this is not properly taken into account.