Causes of exceptional atmospheric circulation changes in the Southern Hemisphere
Article first published online: 30 JUL 2004
Copyright 2004 by the American Geophysical Union.
Geophysical Research Letters
Volume 31, Issue 14, July 2004
How to Cite
2004), Causes of exceptional atmospheric circulation changes in the Southern Hemisphere, Geophys. Res. Lett., 31, L14205, doi:10.1029/2004GL019952., , , , , and (
- Issue published online: 30 JUL 2004
- Article first published online: 30 JUL 2004
- Manuscript Accepted: 7 JUL 2004
- Manuscript Revised: 22 JUN 2004
- Manuscript Received: 11 MAR 2004
 We demonstrate that recent observed trends in the annual and austral summer Southern Hemisphere Annular Mode (SAM) are unlikely to be due to internal climate variability, since they exceed any equivalent-length trends in a millennial General Circulation Model (GCM) control run with constant forcings. In contrast we show that observed trends in the SAM are consistent with the combined effects of anthropogenic and natural forcings in GCM simulations. As these trends begin prior to stratospheric ozone depletion we challenge the assertion that this process is primarily responsible for changes in the SAM. Moreover, anthropogenic forcings have a larger effect on the austral summer SAM in combination with natural forcings than when acting in isolation.