Sir, - An item on ozone depletion (IT, November 18th) referred to my article on the subject in the current issue of Technology Ireland. I welcome any discussion on this important subject, but I feel that misunderstandings may have arisen from the Irish Times item on a few points.
Severe ozone depletion occurs in the atmosphere over Antarctica from August to October, but the ozone concentration over that region subsequently recovers each year. The "ozone hole" is not permanent. Stratospheric ozone depletion in the Northern Hemisphere, particularly in middle latitudes, occurs on a much smaller scale. The levels of ozone over Ireland should not cause alarm. However the trend towards reduced levels aloft, even in middle latitudes, is a matter for concern and justifies monitoring and research.
While the scientific community expects that this general trend for the depletion of the ozone layer will continue for some more years, it is not possible to forecast the levels in any particular year. Conditions in 1997 may not in fact be worse than in 1996.
The low concentrations of stratospheric ozone and corresponding increased intensities of UVB radiation, measured in Ireland in late February and early
March this year, were associated with a polar vortex with depleted ozone drifting down from the North Pole close to Ireland. Such episodes may reoccur, but the UVB intensities involved in these isolated incidents in early spring do not pose a threat to public health. It is too much exposure to UV radiation and long periods of sunbathing in summer sun which cause increased risks of contracting skin cancer.
Finally, while ozone depletion and climate change are linked in a few respects, these phenomena are largely independent. - Yours, etc,
Chief Scientist, Valentia Observatory,
Cahirciveen, Co. Kerry.