Developing ozone hole approaches Europe

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dinsdag 29 maart 2011

An exceptionally large area of depleted ozone has formed over the North Pole, and scientists warn that it could settle over Scandinavia and Eastern Europe on 30-31 March.

The fast-thinning Arctic ozone layer was first detected by an international network of over 30 ozone sounding stations spread across the Arctic and sub-Arctic, and coordinated by the Alfred Wegener Institute for Polar and Marine Research.

The institute's latest predictions, based on data collated from the European Centre for Medium Range Weather Forecasts, are that it will affect parts of Scandinavia and Eastern Europe on 30 March and 31 March.

"The ozone loss is still going on at high rates and we don't see an end to that for at least 10-14 days," Markus Rex, an atmospheric scientist at the Alfred Wegener Institute, told EurActiv.

"The degree of ozone loss in the Arctic is clearly larger than in any winter so far," he added.

Polar station measurements showed that around half of the ozone had been destroyed at some latitudes, he said, and the Arctic was on track for a record loss of ozone, which protects earth from ultra-violet (UV) radiation.

Data is still being collated and a collection of atmospheric scientists from around the world plan to release a statement on the phenomenon at a conference in Vienna on 4 April.

But it was "absolutely possible" that the thinning parts of the ozone layer could turn into an "ozone hole," Rex said.

Another scientist who had signed the Alfred Wegener Institute's statement, Hugue de Backer of Belgium's Royal Meteorological Institute, said that this would only happen, if quantities of ozone fell below 200 Dobson units (the standard measure of atmospheric ozone concentrations).

"The levels above central Siberia now are about 250 Dobson units, which is quite low," he told EurActiv.

Ultra-violet radiation (UV) exposure from the depleted ozone layer is less dangerous than that found in the tropics, but scientists still advised caution.

"People should be vigilant but they shouldn't be worried," Gier Braathen, a senior scientific officer at the World Meteorological Organisation, told EurActiv.

"You can protect yourself by keeping informed, putting on a wide-brimmed hat and sun screen, and not spending too many hours outdoors."

A "severe depletion" of ozone was taking place, he said, because "this is among the most severe winters we have seen". But it was still too soon to say if it would be the worst ever, he counselled.

Link with climate change

The destruction of the Earth's ozone is caused by a chemical reaction between atomic chlorine and bromine that takes place in the stratosphere at the sort of very low temperatures most commonly found in the Antarctic.

These halogen and halon atoms entered the atmosphere in the form of man-made chlorofluorocarbons (CFC's) which were commonly used in appliances such as aerosols, flame retardants and refrigerants from the 1920s onwards.

Although they were banned by the Montreal Protocol in 1987, Braathen estimated that ozone levels would not recover to their 1980 levels until 2050.

Before then there could be more ozone scares, due to climate change. 

"We cannot rule it out," Braathen said. "It sounds paradoxical but when it gets warmer down here [on the ground], it gets colder in the stratosphere. This is what all the models predict."

"There could absolutely be a climate link here," he said.

Most man-made ozone depleting substances are also very potent greenhouse cases, notes the European Commission, with some of them 14,000 times stronger than CO2. Therefore, eliminating those substances also contributes significantly to the prevention of climate change, it says.

However, the Commission admits that "much remains to be done to ensure the continuous recovery of the ozone layer and to reduce the impact of ozone depleting substances on climate change".


Bron: euractiv.com

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