National Institute of Water and Atmospheric Research (NIWA)

Ozone depleting substance found to be rising

NIWA researchers have made a prominent contribution to new research showing the international treaty to protect the ozone layer is working ­- despite the discovery of increased levels of ozone-depleting hydrogen chloride in the Northern Hemisphere.

Measurements made at NIWA’s atmospheric research laboratory at Lauder are a key component in an article in the latest edition of one of the world’s most prestigious scientific journals, Nature. The international team of scientists, including NIWA researchers, Dan Smale and John Robinson, based their findings on measurements from a network of stations across the globe, including Lauder in Central Otago. The data from these stations was backed up by satellite observations and model simulations.

The article features a study about an unexpected increase in hydrogen chloride detected 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 shows the increase is a result of a temporary but prolonged anomaly in atmospheric circulation. It refutes the possibility of rogue emissions of ozone-depleting substances and confirms that the ozone layer will likely fully recover during the second half of this century.  However, the study also shows the expected evolution of ozone-destroying chemicals in the atmosphere is shown to be more complex than a smooth decline.

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

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

 The Lauder site is a key site, one of only a handful operating the in the Southern Hemisphere, and the longest in operation.

The scientists found the increase of hydrogen chloride above the Northern Hemisphere was related to circulation patterns around the globe.

One of the study authors said: “Our observations do not challenge the general view that the Montreal Protocol is working. They rather show that atmospheric variability and perhaps climate change can significantly modify the path towards full recovery. It will be a bumpy ride rather than a smooth evolution”.

This is the second time research conducted by NIWA researchers has featured in Nature in the past six months.

In May, Drs Alison Kohout, Mike Williams and Sam Dean reported on a breakthrough in understanding one of the key processs driving changes in sea ice.

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