An ozone hole forms above Antarctica every year. This year it reached its max on Sept. 22, 2012, but it is smaller than in the past because of usual variations in Antarctic weather conditions. The ozone hole reached its largest size six years ago, in 2006, when it covered more than 11 million square miles. World adherence to the Montreal Protocol-an international treaty that regulated the use of CFCs-has helped protect the ozone layer. Scientists expect the ozone layer to return to 1980 levels by 2050.
GCMD keywords can be found on the Internet with the following citation:
Olsen, L.M., G. Major, K. Shein, J. Scialdone, S. Ritz, T. Stevens, M. Morahan, A. Aleman, R. Vogel, S. Leicester, H. Weir, M. Meaux, S. Grebas, C.Solomon, M. Holland, T. Northcutt, R. A. Restrepo, R. Bilodeau, 2013. NASA/Global Change Master Directory (GCMD) Earth Science Keywords. Version 184.108.40.206.0