Earth's protective ozone layer is well on track to recovery in the next few decades thanks to concerted international action against ozone depleting substances, according to a new assessment by 300 scientists.
The Assessment for Decision-Makers, a summary document of the Scientific Assessment of Ozone Depletion 2014, is being published by the United Nations Environment Programme (UNEP) and the World Meteorological Organization (WMO), and is the first comprehensive update in four years.
Pic.1. The images above show the Antarctic ozone hole on September 16 (the International Day for the Preservation of the Ozone Layer) in the years 1979, 1987, 2006, and 2011. The first two maps are based on data from the Total Ozone Mapping Spectrometer (TOMS) on the Nimbus-7 satellite. The other two maps are made with data from the Ozone Monitoring Instrument on the Aura satellite. Though taken by different instruments, the data sets have all been cross-calibrated and reanalyzed by scientific models.
The stratospheric ozone layer, a fragile shield of gas, protects Earth from harmful ultraviolet rays of the sun. Without the Montreal Protocol and associated agreements, atmospheric levels of ozone depleting substances could have increased tenfold by 2050. According to global models, the Protocol will have prevented 2 million cases of skin cancer annually by 2030, averted damage to human eyes and immune systems, and protected wildlife and agriculture, according to UNEP.
The phase-out of ozone depleting substances has had a positive spin-off for the global climate because many of these substances are also potent greenhouse gases. However, the assessment report cautions that the rapid increase in certain substitutes, which are themselves also potent greenhouse gases, has the potential to undermine these gains. The assessment also notes that there are possible approaches to avoiding the harmful climate effects of these substitutes.
"There are positive indications that the ozone layer is on track to recovery towards the middle of the century. The Montreal Protocol -- one of the world's most successful environmental treaties -- has protected the stratospheric ozone layer and avoided enhanced UV radiation reaching the earth's surface," said UN Under-Secretary-General and UNEP Executive Director Achim Steiner.
"However, the challenges that we face are still huge. The success of the Montreal Protocol should encourage further action not only on the protection and recovery of the ozone layer but also on climate. On September 23, the UN Secretary General will host Heads of State in New York in an effort to catalyse global action on climate. The Montreal Protocol community, with its tangible achievements, is in a position to provide strong evidence that global cooperation and concerted action are the key ingredients to secure the protection of our global commons," he added.
"International action on the ozone layer is a major environmental success story," said WMO Secretary-General Michel Jarraud. "This should encourage us to display the same level of urgency and unity to tackle the even greater challenge of climate change. This latest assessment provides solid science to policy-makers about the intricate relationship between ozone and climate and the need for mutually-supportive measures to protect life on earth for future generations."
"Human activities will continue to change the composition of the atmosphere. WMO's Global Atmosphere Watch programme will therefore continue its crucial monitoring, research and assessment activities to provide scientific data needed to understand and ultimately predict environmental changes, as it has done for the past 25 years" said Mr Jarraud.
Actions taken under the Montreal Protocol on Substances that Deplete the Ozone Layer are enabling the return of the ozone layer to benchmark 1980 levels.
The climate benefits of the Montreal Protocol could be significantly offset by projected emissions of HFCs (hydrofluorocarbons) used to replace ozone depleting substances.
The annual Antarctic ozone hole has caused significant changes in Southern Hemisphere surface climate in the summer.
CO2, Nitrous Oxide and Methane will have an increasing influence on the ozone layer
The Scientific Assessment Panel is expected to present the key findings of the new report at the annual Meeting of the Parties to the Montreal Protocol, to be held in Paris in November 2014. The full body of the report will be issued in early 2015.
The Scientific Assessment of Ozone Depletion 2014 was prepared and reviewed by 282 scientists from 36 countries (Argentina, Australia, Austria, Belgium, Botswana, Brazil, Canada, People's Republic of China, Comoros, Costa Rica, Cuba, Czech Republic, Denmark, Finland, France, Germany, Greece, India, Israel, Italy, Japan, Korea, Malaysia, New Zealand, Norway, Poland, Russia, South Africa, Spain, Sweden, Switzerland, The Netherlands, Togo, United Kingdom, United States of America, Zimbabwe.)