Science Update: Detecting the solar signal in the tropical stratosphere

In a recent ACPD article, G. Chiodo and co-authors use the WACCM chemistry-climate model to perform transient simulations looking at the solar cycle in the tropics. They investigate the relative role of volcanic eruptions, ENSO, and the QBO signals in the tropical stratosphere temperatures and ozone commonly attributed to the 11-year solar cycle. Simulations from 1960-2004 were carried out and a multiple regression technique used to diagnose the 11-year solar signal. Results show that most of the solar-induced lower stratospheric temperature and ozone increase diagnosed in the simulation including all forcing factors is due to the two major volcanic eruptions during the period studied (El Chichón and M. Pinatubo), which were concurrent with periods of high solar activity. Thus, the portion of decadal variability that can unambiguously be linked to the solar cycle may be smaller than previously thought. The full abstract can be found here.