New research has identified clear signs that the hole in the Antarctic ozone layer is beginning to close.
Scientists from the University of Leeds were part of an international team led by Professor Susan Solomon of the Massachusetts Institute of Technology to confirm the first signs of healing of the ozone layer, which shields life on Earth from the sun's harmful ultraviolet rays.
Recovery of the hole has varied from year to year, due in part to the effects of volcanic eruptions.
But accounting for the effects of these eruptions allowed the team to show that the ozone hole is healing, and they see no reason why the ozone hole should not close permanently by the middle of this century.
These encouraging new findings, published today in the journal Science , show that the average size of the ozone hole each September has shrunk by more than 1.7 million square miles since 2000 -- about 18 times the area of the United Kingdom.
The research attributes this improvement to the 1987 Montreal Protocol, which heralded a ban the use of chlorofluorocarbons (CFCs) -- then widely used in cooling appliances and aerosol cans.
Professor Solomon said: "We can now be confident that the things we've done have put the planet on a path to heal. We decided collectively, as a world, 'Let's get rid of these molecules'. We got rid of them, and now we're seeing the planet respond." Co-author Dr Ryan R Neely III , a Lecturer in Observational Atmospheric Science at Leeds, said: "Observations and computer models agree; healing of the Antarctic ozone has begun. We were also able to quantify the separate impacts of man-made pollutants, changes in temperature and winds, and volcanoes, on the size and magnitude of the Antarctic ozone hole."
University of Leeds colleague and co-author Dr Anja Schmidt , an Academic Research Fellow in Volcanic Impacts, said: "The Montreal Protocol is a true success story that provided a solution to a global environmental issue."
She added that the team's research had shed new light on the part played by recent volcanic eruptions - such as at Calbuco in Chile in 2015 - in Antarctic ozone depletion.
"Despite the ozone layer recovering, there was a very large ozone hole in 2015," she said. "We were able to show that some recent, rather small volcanic eruptions slightly delayed the recovery of the ozone layer.
"That is because such eruptions are a sporadic source of tiny airborne particles that provide the necessary chemical conditions for the chlorine from CFCs introduced to the atmosphere to react efficiently with ozone in the atmosphere above Antarctica. Thus, volcanic injections of particles cause greater than usual ozone depletion."
The ozone hole begins growing each year when the sun returns to the South Polar cap from August, and reaches its peak in October - which has traditionally been the main focus for research.
The researchers believed they would get a clearer picture of the effects of chlorine by looking earlier in the year in September, when cold winter temperatures still prevail and the ozone hole is opening up. The team showed that as chlorine levels have decreased, the rate at which the hole opens up in September has slowed down.
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Further information
Dr Anja Schmidt is an Academic Research Fellow in Volcanic Impacts and Hazards at the University of Leeds' School of Earth and Environment . Dr Ryan R. Neely III is a Lecturer in Observational Atmospheric Science at the Leeds-based National Centre for Atmospheric Science and Leeds' School of Earth and Environment.
Scientists from the Atmospheric Chemistry Observations and Modeling (ACOM) Laboratory at National Center for Atmospheric Research in Boulder, Colorado, also worked on the research, which was supported in part by the National Science Foundation and the US Department of Energy.
* The paper, Emergence of Healing in the Antarctic Ozone Layer, is published in Science today. For copies of the paper, interviews, images or further information, contact Gareth Dant, University of Leeds Media Relations Manager, on 0113 343 3996 or email g.j.dant@leeds.ac.uk .
National Centre for Atmospheric Science
The National Centre for Atmospheric Science (NCAS) is a world leader in atmospheric science, a multi-million pound research centre, funded by the Natural Environment Research Council (NERC). NCAS carries out research in climate science, atmospheric composition and air quality, physics of the atmosphere (including hazardous and extreme weather) and provides the UK community with state-of-the-art technologies and scientific facilities for observing and modelling the atmosphere, including a world-leading research aircraft.
University of Leeds
The University of Leeds is one of the largest higher education institutions in the UK, with more than 31,000 students from 147 different countries, and a member of the Russell Group research-intensive universities. We are a top 10 university for research and impact power in the UK, according to the 2014 Research Excellence Framework, and positioned as one of the top 100 best universities in the world in the 2014 QS World University Rankings. http://www.leeds.ac.uk
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