From a University of Waterloo press release (h/t to commenter Rob)
WATERLOO, Ont. (Tuesday, Sept. 16, 2008) — A University of Waterloo scientist says that cosmic rays are a key cause for expanding the hole in the ozone layer over the South Pole — and predicts the largest ozone hole will occur in one or two weeks.
Qing-Bin Lu, a professor of physics and astronomy who studies ozone depletion, said that it was generally accepted for more than two decades that the Earth’s ozone layer is depleted by chlorine atoms produced by sunlight-induced destruction of chlorofluorocarbons (CFCs) in the atmosphere. But more and more evidence now points to a new theory that the cosmic rays (energy particles that originate in space) play a major role.
The ozone layer is a layer in Earth’s atmosphere that contains high concentrations of ozone. It absorbs almost all of the sun’s high-frequency ultraviolet light, which is potentially damaging to life on Earth and causes diseases such as skin cancer and cataracts. The Antarctic ozone hole can be larger than the size of North America.
Lu said that data from several sources, including NASA satellites, show a strong correlation between cosmic ray intensity and ozone depletion. Lab measurements demonstrate a mechanism by which cosmic rays cause drastic reactions of ozone-depleting chlorine inside polar clouds.
Satellite data in the period of 1980-2007, covering two full 11-year solar cycles, demonstrate the significant correlation between cosmic rays and ozone depletion.
“This finding, combined with laboratory measurements, provides strong evidence of the role of cosmic-ray driven reactions in causing the ozone hole and resolves the mystery why a large discrepancy between the sunlight-related photochemical model and the observed ozone depletion exists,” Lu said.
For example, the most recent scientific assessments of ozone depletion by the World Meteorological Organization and the United Nations Environment Programme, which use photochemical models, predict ozone will increase by one to 2.5 per cent between 2000 and 2020 and Antarctic springtime ozone is projected to increase by five to 10 per cent between 2000 and 2020.
In sharp contrast, Lu said his study predicts the severest ozone loss — resulting in the largest ozone hole — will occur over the South Pole this month. The study also predicts another large hole will probably occur around 2019.