The hole in the ozone layer can be seen in the dark-blue areas in this image of Earth, but the problem appears to be easing in the upper stratosphere.
Ozone destruction in the upper atmosphere has begun to slow - a first sign that the international ban on emissions of chlorofluorocarbons is working.
The good news for the protective ozone layer was discovered by researchers analysing measurements made by three NASA satellites over the past 20 years.
The team leader, Michael Newchurch, of the University of Alabama, said the recent changes they had observed were small but important. 'This is the beginning of a recovery of the ozone layer. We had a monumental problem of global scale that we have started to resolve.'
He said the findings, to be published in the Journal of Geophysical Research, meant the ban on CFCs and other halogenated hydrocarbons should continue.
Scientists had known from research in Australia and overseas that phasing out these chemicals from 1989 had already led to a slowdown in the accumulation of chlorine in the atmosphere. But the satellite study is the first to observe an associated reduction in ozone depletion."
Envirotreaties do work. Stopping greenhouse would be harder but it can be done. Pity the Bush administration thinks otherwise.