Intl ozone treaty working despite anomaly: scientists

New Zealand government scientists said Thursday that an international treaty to stop the use of ozone-depleting gases was still working despite a study showing new damage to the ozone layer in the Northern Hemisphere.

The researchers from the National Institute of Water and Atmospheric Research (NIWA) said they had also contributed to an article in the scientific journal, Nature, that reported an unexpected rise in hydrogen chloride in the Northern Hemisphere since 2007.

The increase appeared to contradict the success of the Montreal Protocol introduced in 1987 to protect the ozone layer by banning production of ozone-depleting substances.

The study showed the increase was a result of a temporary, but prolonged anomaly in atmospheric circulation, NIWA researcher Dan Smale said in a statement.

It refuted the possibility of rogue emissions of ozone- depleting substances and confirmed that the ozone layer would likely fully recover during the second half of this century.

Measurements made at NIWA's atmospheric research laboratory at Lauder, in the South Island, were a key component in an article by international team of scientists.

"NIWA's role in this research is to provide high quality continuous measurements in a data sparse region of the globe. We had to make sure our data was bomb proof," Smale said.

The ozone layer shields the biosphere from harmful ultraviolet radiation and is an essential part of the climate system.