By merging more than a decade of atmospheric data from European satellites, scientists have compiled a homogeneous long-term ozone record that allows them to monitor total ozone trends on a global scale — and the findings look promising.

The thinning of the ozone layer is caused by chemicals such as human-produced bromine and chlorine gases that have long lifetimes in the atmosphere. The Montreal Protocol (1987) was introduced to regulate and phase out the production of these substances. Its effect can clearly be seen in the satellite observations of ozone and these chemicals.

"Our analysis shows that upper stratospheric ozone declined at northern and southern mid-latitudes at roughly 7% per decade during 1979—97, consistent with earlier studies based on data from satellites and ground networks. A clear statistically significant change of trend can be seen around 1997. The small increase (of 0.8—1.4% per decade) observed thereafter, from 1997 to 2008, is however not yet statistically different from a zero trend. We hope to see a significant recovery of (upper stratospheric) ozone in the next years using longer, extended satellite time-series," Urban said.

"We found a global slightly positive trend of ozone increase of almost 1% per decade in the total ozone from the last 14 years: a result that was confirmed by comparisons with ground-based measurements," said Diego G. Loyola R. who worked on the project with colleagues from the German Aerospace Center (DLR).

For more information: http://www.esa.int/esaEO/SEMHSZJVUZF_planet_0.html

From: R. Greenway, ENN
Published September 22, 2009 06:39 AM