The observed increase in Southern Annular Mode is due to the ozone hole, not to increased greenhouse gases

The amplitude of the Southern Annular Mode of variability in sea level pressure has increased significantly since records began in the 1950s. Roscoe & Haigh (2007), using data to 2006, showed that the increase in SAM correlated with either the ozone hole or the increase in greenhouse gases, but the correlation with the ozone hole was more significant. However, it was difficult to quantify the meaning of this greater significance because of the then similarity between the trends in greenhouse gases and the CFCs that caused the ozone hole – esoteric statistical concepts had to be used. The trends have now diverged, and a measure of actual ozone loss in the ozone hole can be used instead of CFCs. This update can use the more familiar statistical method of Student's t-test to show that the correlation of SAM with the ozone hole is highly significant, but there is negligible correlation with increased greenhouse gases.