Ozone layer vanishing at increased rate

The ozone layer in the northern hemisphere is being depleted twice as fast as previously believed, the US Environmental Protection Agency said on April 4.

New data from NASA showed that ozone had thinned by 4 to 5% since 1978. A 1% reduction in the ozone layer is associated with a 2% increase in skin cancers. The new figures suggest an extra 200,000 cases of skin cancer in the United States over the next 50 years.

The new data also showed ozone depletion occurring during spring, rather than only in winter, as scientists had previously believed. This is significant because increased ultraviolet radiation in spring can stunt plant growth and the growth of plankton, the microscopic organisms which are the starting point of the ocean food chain.

Under a treaty negotiated in London last June, signatory nations agreed to eliminate ozone-destroying CFCs, halons and carbon tetrachloride by 2000 and methyl chloroform by 2005. A 1987 treaty called for a 50% cut in CFCs and halons by 2000.

Even with the accelerated schedule, the atmosphere is so full of long-lived ozone-destroying chemicals that depletion will continue throughout the next century.

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