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The 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, which was made available to the Ghana News Agency on Saturday, is being published by the United Nations Environment Programme (UNEP) and the World Meteorological Organisation (WMO), and is the first comprehensive update in four years. The stratospheric ozone layer, a fragile shield of gas, protects the Earth from harmful ultraviolet rays of the sun. According to the document, without the Montreal Protocol and associated agreements, atmospheric levels of ozone depleting substances could have increased tenfold by 2050. Global models indicate that the Protocol would prevent two million cases of skin cancer annually by 2030, avert damage to human eyes and immune systems, and protect 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 potent greenhouse gases, has the potential to undermine these gains. The assessment notes that there were possible approaches to avoiding the harmful climate effects of those 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 Ultra Violet (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 co-operation and concerted action are the key ingredients to secure the protection of our global commons," he said. Michel Jarraud, WMO Secretary-General, said: "International action on the ozone layer is a major environmental success story. 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." The key findings are that the 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. According to the report the climate benefits of the Montreal Protocol could be significantly offset by projected emissions of HFCs (hydrofluorocarbons) used to replace ozone depleting substances. It said the annual Antarctic ozone hole has caused significant changes in Southern Hemisphere surface climate in the summer. The report said what happened to the ozone layer in the second half of the 21st century would largely depend on concentrations of carbon dioxide (CO2), methane and nitrous oxide - the three main long-lived greenhouse gases in the atmosphere. It said, overall, CO2 and methane tended to increase global ozone levels. By contrast, nitrous oxide, a by-product of food production, was both a powerful greenhouse gas and an ozone depleting gas, and was likely to become more important in future ozone depletion. The Scientific Assessment Panel is expected to present the key findings of the 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.