Signatures of the Antarctic ozone hole in Southern Hemisphere surface climate change

1 Roughly 90% of atmospheric ozone is found in the lower stratosphere in the ozone layer. Since about the 1970s, anthropogenic emissions of ozone-depleting gases have led to depletion of ~3–4% of the total overhead ozone averaged over the globe1. The strongest depletion is found over Antarctica during spring, when photochemical processes combine with a unique set of meteorological conditions to greatly increase the effectiveness of ozone-depleting gases, and more than half of the total overhead ozone is destroyed. Characteristics of the resulting Antarctic ozone hole are reviewed in refs 1 and 2, and the identification and attribution of the phenomenon was recently celebrated in a special edition of Nature (http://www.nature.com/nature/focus/ ozonehole/). The Antarctic ozone hole is evident in ozone observations taken every spring since about the early 1980s1. Its annual onset coincides with the return of sunlight to the cold polar stratosphere during September/October, and its decay with the collapse of the stratospheric vortex during November/December1,2. The most obvious surface impact is an increase in ultraviolet radiation reaching the surface1. Over the past decade, however, it has become clear that the ozone hole is also associated with widespread changes in the Southern Hemisphere tropospheric circulation and surface climate. Our purpose here is to review the evidence that suggests that the Antarctic ozone hole has had a demonstrable effect on the surface climate of the Southern Hemisphere.