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Friday, 19 November, 1999, 15:54 GMT
Scientists join forces to study Arctic ozone
Ozone thinning occurs at the end of winter

An international team of scientists has been gathered together to undertake the biggest study yet of ozone levels over the Arctic.

Researchers from the EU, Canada, Iceland, Japan, Norway, Poland, Russia, Switzerland and the US will examine the processes that control ozone amounts during the Arctic winter more than 20 kilometres above the Earth.

This project to measure the ozone, and other atmospheric gases, will use satellites, planes, heavy-lift and small balloons, and ground-based instruments.

Ozone is a molecule in which three oxygen atoms are joined together. It is constantly being made and destroyed in the stratosphere. It plays a crucial role in protecting life below by filtering out harmful ultraviolet radiation (less than 290 nanometres) coming from the Sun.

This radiation can damage DNA, thereby leading to the formation of skin cancers.

Chlorine compounds

It has been known for some time that man-made chlorine and bromine compounds can upset the balance of chemistry at high altitudes leading to a thinning of ozone.

The chlorine compounds have been produced for use as refrigerants, aerosol sprays, solvents and foam blowing agents, while bromine-containing halons have been used in fire extinguishers.

World governments have now moved to restrict their use.

Nevertheless, very low levels of ozone have been observed over the Arctic in several winters during the 1990s, raising concerns that an ozone "hole" might form like the one detected over the South Pole.

A northern hole is potentially more dangerous because it would affect areas with higher populations.

The new study, which will look at ozone levels from November 1999 through to March 2000, is a collaborative effort involving scientists working on Europe's Theseo (Third European Stratospheric Experiment on Ozone) campaign and the Nasa-sponsored Solve (Sage III Ozone Loss and Validation Experiment) campaign.

Computer models

Researchers will examine the processes that control ozone amounts during the Arctic winter at mid to high latitudes. It was a failure to properly understand some of the chemistry over the South Pole that led to inaccurate forecasts about ozone depletion in the Southern Hemisphere.

Scientists want to make sure the computer models they use to project future depletion over the North are better able to handle the complex processes at work.

"We generally understand the chemistry but we are not able to quantify it exactly," Dr Marielle Guirlet, from the European Ozone Research Co-ordinating Unit in Cambridge, UK, told BBC News Online.

"When you compare the models with the measurements taken at the end of the winter you have broad agreement, but when you look in closer detail it seems that the models usually underestimate the ozone loss. This would indicate we are missing some process or are misunderstand it."

The scientists particularly want to know what impact any human-induced warming of the atmosphere might have on ozone levels. Some recent research has suggested that global warming, should it happen, could accelerate ozone thinning.

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See also:
16 Nov 99 |  Sci/Tech
Arctic sea ice gets thinner
18 Nov 99 |  Sci/Tech
Climate change warning
 |  Sci/Tech
Global warming could starve polar bears

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