title: Quantifying the ozone and ultraviolet benefits already achieved by the Montreal Protocol.
abstract: Chlorine- and bromine-containing ozone-depleting substances (ODSs) are controlled by the 1987 Montreal Protocol. In consequence, atmospheric equivalent chlorine peaked in 1993 and has been declining slowly since then. Consistent with this, models project a gradual increase in stratospheric ozone with the Antarctic ozone hole expected to disappear by ∼2050. However, we show that by 2013 the Montreal Protocol had already achieved significant benefits for the ozone layer. Using a 3D atmospheric chemistry transport model, we demonstrate that much larger ozone depletion than observed has been avoided by the protocol, with beneficial impacts on surface ultraviolet. A deep Arctic ozone hole, with column values <120 DU, would have occurred given meteorological conditions in 2011. The Antarctic ozone hole would have grown in size by 40% by 2013, with enhanced loss at subpolar latitudes. The decline over northern hemisphere middle latitudes would have continued, more than doubling to ∼15% by 2013.
authors.affiliation: School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK.|National Centre for Earth Observation (NCEO), University of Leeds, Leeds LS2 9JT, UK.
authors.forename: M P
authors.initials: MP
authors.lastname: Chipperfield
authors.affiliation: School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK.|National Centre for Earth Observation (NCEO), University of Leeds, Leeds LS2 9JT, UK.
authors.forename: S S
authors.identifier: http://orcid.org/0000-0003-3854-5383
authors.initials: SS
authors.lastname: Dhomse
authors.affiliation: School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK.|National Centre for Atmospheric Science (NCAS), UK.
authors.forename: W
authors.initials: W
authors.lastname: Feng
authors.affiliation: National Institute of Water and Atmospheric Research (NIWA), Lauder Private Bag 50061, New Zealand.
authors.forename: R L
authors.initials: RL
authors.lastname: McKenzie
authors.affiliation: National Institute for Public Health and the Environment, PO Box 1, Bilthoven 3720 BA, The Netherlands.
authors.forename: G J M
authors.initials: GJM
authors.lastname: Velders
authors.affiliation: National Centre for Atmospheric Science (NCAS), UK.|Department of Chemistry, University of Cambridge, Cambridge CB2 1EW, UK.
authors.forename: J A
authors.initials: JA
authors.lastname: Pyle