Ozone hole to close in 50 years

Thanks to curbs on chlorofluorocarbons (CFCs), the ozone layer should soon start to repair itself, providing that disuse of the chemicals continues, scientists attending the recent Stratospheric Processes and their Role in Climate (SPARC) Second General Assembly in Mar del Plata, Argentina, said. The delegates made the prediction after 300 climate scientists studied fresh ozone data, but warned that governments must tackle the wider issue of reducing greenhouse gas emissions, if any real progress on ozone is to be achieved.

The revelation was made less than two months after the largest and deepest ever hole was discovered over the Antarctic (see related story) and after citizens of cities in southern Chile and Argentina were warned by authorities to remain indoors, due to the problem (see related story). The new prediction was based on evidence that CFC levels in the lower atmosphere are falling, since a worldwide ban was introduced in 1987.

Professor Alan O’Neill, Chair of the SPARC 2000 Scientific Committee and a climate expert at Reading University in England, said that the recovery would probably not begin for a few years, and would not show a steady pattern, due to yearly natural fluctuations in weather patterns. He also said that a cooling of the lower atmosphere due to greenhouse gas emissions could delay the closing of the ozone hole by up to a decade.

“We are now seeing evidence that the international bans or controls on ozone destroying substances are now taking effect: amounts of these substances are, overall, falling in the lower atmosphere and our prediction is that ozone amounts will recover over the next 50 years or so,” O’Neill said. “Scientists have gained a detailed understanding of how man-made substances (containing chlorine and bromine) destroy ozone. We can explain why much more ozone is destroyed over the Antarctic than over the Arctic, and why the ozone hole is bigger during some years than during others,” he added.