Despite jump in CFC-11, ODS quantities have declined since the last assessment in 2014, says multi-national study.
Image of the largest area of Antarctic thinning ever recorded, in September 2000
Courtesy of NASA via Wikimedia Commons
A new assessment of ozone depletion in the atmosphere concludes that actions taken under the Montreal Protocol have led to decreases in the atmospheric abundance of controlled ozone-depleting substances (ODS) and the start of the recovery of stratospheric ozone.
The report, “Scientific Assessment of Ozone Depletion: 2018” – an update of the last assessment published in 2014 – was produced by the World Meteorological Organization, United Nations Environment Programme, U.S. National Oceanic and Atmospheric Administration, U.S. National Aeronautics and Space Administration and the European Commission.
While the report observed continued progress in restoring the ozone layer, it acknowledged “an unexpected increase” in global total emissions of ozone-depleting CFC-11. “Global CFC-11 emissions derived from measurements by two independent networks increased after 2012, thereby slowing the steady decrease in atmospheric concentrations reported in previous Assessments.”
At the 30th Meeting of the Parties to the Montreal Protocol (MOP 30) in Quito, Ecuador last week, the Parties committed to provide all available data on the illegal use and production of ozone-depleting CFC-11, following the presentation of the Environmental Investigation Agency's latest report on the use of CFC-11 in China.
Nonetheless, atmospheric abundances of both total tropospheric chlorine and total tropospheric bromine from long-lived ODS controlled under the Montreal Protocol “have continued to decline since the 2014 Assessment,” the report said.
The decline in ODS made a substantial contribution to the following observed ozone trends:
– The Antarctic ozone hole is recovering, while continuing to occur every year. As a result of the Montreal Protocol much more severe ozone depletion in the polar regions has been avoided.
– Outside the polar regions, upper stratospheric ozone has increased by 1–3% per decade since 2000.
– No significant trend has been detected in global total column ozone over the 1997–2016 period with average values in the years since the last Assessment remaining roughly 2% below the 1964–1980 average.
Ozone layer changes in the latter half of this century will be complex, with projected increases and decreases in different regions, the report said. Northern Hemisphere mid-latitude total column ozone is expected to return to 1980 abundances in the 2030s, and Southern Hemisphere mid-latitude ozone to return around mid-century. The Antarctic ozone hole is expected togradually close, with springtime total column ozone returning to 1980 values in the 2060s.
The report documents the advances in scientific understanding of ozone depletion reflecting the thinking of the many international scientific experts who have contributed to its preparation and review. “These advances add to the scientific basis for decisions made by the Parties to the Montreal Protocol,” it said.
The report also noted that the global HFC phase-down plan developed under the Kigali Amendment to the Montreal Protocol in 2016 is projected to avoid temperature increase of 0.2°C to 0.4°C. This is “substantial in the context of the 2015 Paris Agreement, which aims to keep global temperature rise this century to well below 2°C above pre-industrial levels,” it said.
Continued success of the Montreal Protocol in protecting stratospheric ozone will depend on “continued compliance,” the report said.