Ozone layer no longer decreasing

Total Ozone Mapping Spectrometer (TOMS) image of the ozone hole over Antarctica in Septemb...

A new report suggests that international efforts to halt the destruction of the ozone layer have been successful. Launched on the UN International Day for Preservation of the Ozone Layer, the report by 300 scientists also provides new information about the net effects on Earth’s climate, and also the effects of climate change on the ozone later moving forward.

The UN International Day for the Preservation of the Ozone Layer on 16th September is to commemorate the signature date in 1987 of the Montreal Protocol on Substances that Deplete the Ozone Layer. This international treaty aimed to protect the ozone layer by phasing out use of harmful substances such as chlorofluorocarbons (CFCs) believed to be responsible for ozone depletion and contributing to the greenhouse effect. The report reaffirms that the Montreal Protocol is working; “It has protected the stratospheric ozone layer from much higher levels of depletion by phasing out production and consumption of ozone depleting substances.”

Given that many substances that deplete the ozone layer are also potent greenhouse gases the net benefits are two-fold; first the arrest of ozone-layer depletion; secondly, the reduction of greenhouse effect, both of which should impact climate change.

The report finds that the global ozone is no longer decreasing though not yet increasing, and that due to the Montreal Protocol the ozone layer outside the polar regions is projected to recover to pre-1980 levels by the mid 21st century, a recovery that may be sped up if greenhouse gases cool the upper stratosphere.

The springtime hole over the Antarctic however is not projected to recover until much later which may or may not be a good thing according to research from University of Leeds which suggests the hole may be preventing further warming. Here UV levels remain high and the effect on surface climate is becoming evident, leading to important changes in surface temperature and wind patterns. At mid-latitudes, surface UV has remained fairly constant over the past decade.

The mixed news continues: while CFCs have been phased out, demand has risen for replacement substances known as HCFCs (hydrochlorofluorocarbons) and HFCs (hydrofluorocarbons) which are also powerful greenhouse gases. These are predicted to decline over the next decade but are currently increasing faster than four years ago, at an overall rate of approximately 8% per year. For example, HFC-23 is a byproduct of HCFC-22 production and has no impact on the ozone layer, but it is more than 14,000 times more powerful as a greenhouse gas than CO2. However, the overall reduction of of ozone-depleting substances has been five times larger than those initially targeted during the commitment period 2008-2012 as set out by the Kyoto Protocol.

The report stressed that climate change will continue to affect the ozone layer despite efforts because of continued emissions of long-lived greenhouse gases, mainly carbon dioxide, associated with human activities.

Achim Steiner, UN Under-Secretary General and United Nations Environment Programme Executive Director said: “This represents a further potential area for action within the overall climate change challenge. An international group of modellers working with UNEP recently concluded that current commitments and pledges linked with the Copenhagen Accord are unlikely to keep a global temperature rise to under 2°C by 2050. The gap between scientific reality and ambition is estimated to average around 4.7 Gigatonnes of CO2 equivalent per year-a gap that needs to be urgently bridged over the next decade or so if the 2°C target is to be met.

“The ozone-hole issue demonstrates the importance of long-term atmospheric monitoring and research, without which ozone destruction would have continued unabated and might not have been detected until more serious damage was evident,” said WMO Secretary-General Michel Jarraud. “Without the Montreal Protocol and its associated Vienna Convention atmospheric levels of ozone-depleting substances could have increased tenfold by 2050. This in turn could have led to up to twenty million more cases of skin cancer and one hundred and thirty million more cases of eye cataracts, not to speak of damage to human immune systems, wildlife and agriculture,” added Achim Steiner.

The report, the first comprehensive update in four years, was published by theWorld Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP). The executive summary of the Scientific Assessment of Ozone Depletion 2010 will be presented by the Scientific Assessment Panel at the next annual Meeting of the Parties to the Montreal Protocol, to be held in Kampala, Uganda, from 8 to 12 November 2010. The full body of the report will be available in early 2011.

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