Articles | Volume 18, issue 2
Atmos. Chem. Phys., 18, 1379–1394, 2018
Atmos. Chem. Phys., 18, 1379–1394, 2018

Research article 06 Feb 2018

Research article | 06 Feb 2018

Evidence for a continuous decline in lower stratospheric ozone offsetting ozone layer recovery

William T. Ball1,2, Justin Alsing3,4, Daniel J. Mortlock4,5,6, Johannes Staehelin2, Joanna D. Haigh4,7, Thomas Peter2, Fiona Tummon2, Rene Stübi8, Andrea Stenke2, John Anderson9, Adam Bourassa10, Sean M. Davis11,12, Doug Degenstein10, Stacey Frith13,14, Lucien Froidevaux15, Chris Roth10, Viktoria Sofieva16, Ray Wang17, Jeannette Wild18,19, Pengfei Yu11,12, Jerald R. Ziemke13,20, and Eugene V. Rozanov1,2 William T. Ball et al.
  • 1Physikalisch-Meteorologisches Observatorium Davos World Radiation Centre, Dorfstrasse 33, 7260 Davos Dorf, Switzerland
  • 2Institute for Atmospheric and Climate Science, Swiss Federal Institute of Technology Zurich, Universitaetstrasse 16, CHN, 8092 Zurich, Switzerland
  • 3Center for Computational Astrophysics, Flatiron Institute, 162 5th Ave, New York, NY 10010, USA
  • 4Physics Department, Blackett Laboratory, Imperial College London, SW7 2AZ, UK
  • 5Department of Mathematics, Imperial College London, SW7 2AZ, UK
  • 6Department of Astronomy, Stockholm University, 106 91 Stockholm, Sweden
  • 7Grantham Institute – Climate Change and the Environment, Imperial College London, SW7 2AZ, UK
  • 8Federal Office of Meteorology and Climatology, MeteoSwiss, 1530 Payerne, Switzerland
  • 9School of Science, Hampton University, Hampton, VA, USA
  • 10Institute of Space and Atmospheric Studies, University of Saskatchewan, Saskatoon, Canada
  • 11Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO, USA
  • 12NOAA Earth System Research Laboratory, Boulder, CO, USA
  • 13NASA Goddard Space Flight Center, Greenbelt, MD, USA
  • 14Science Systems and Applications Inc., Lanham, MD, USA
  • 15Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
  • 16Finnish Meteorological Institute, Earth Observation, Helsinki, Finland
  • 17School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, USA
  • 18NOAA/NWS/NCEP/Climate Prediction Center, College Park, MD, USA
  • 19Innovim LLC, Greenbelt, MD, USA
  • 20Morgan State University, Baltimore, Maryland, USA

Abstract. Ozone forms in the Earth's atmosphere from the photodissociation of molecular oxygen, primarily in the tropical stratosphere. It is then transported to the extratropics by the Brewer–Dobson circulation (BDC), forming a protective ozone layer around the globe. Human emissions of halogen-containing ozone-depleting substances (hODSs) led to a decline in stratospheric ozone until they were banned by the Montreal Protocol, and since 1998 ozone in the upper stratosphere is rising again, likely the recovery from halogen-induced losses. Total column measurements of ozone between the Earth's surface and the top of the atmosphere indicate that the ozone layer has stopped declining across the globe, but no clear increase has been observed at latitudes between 60° S and 60° N outside the polar regions (60–90°). Here we report evidence from multiple satellite measurements that ozone in the lower stratosphere between 60° S and 60° N has indeed continued to decline since 1998. We find that, even though upper stratospheric ozone is recovering, the continuing downward trend in the lower stratosphere prevails, resulting in a downward trend in stratospheric column ozone between 60° S and 60° N. We find that total column ozone between 60° S and 60° N appears not to have decreased only because of increases in tropospheric column ozone that compensate for the stratospheric decreases. The reasons for the continued reduction of lower stratospheric ozone are not clear; models do not reproduce these trends, and thus the causes now urgently need to be established.

Short summary
Using a robust analysis, with artefact-corrected ozone data, we confirm upper stratospheric ozone is recovering following the Montreal Protocol, but that lower stratospheric ozone (50° S–50° N) has continued to decrease since 1998, and the ozone layer as a whole (60° S–60° N) may be lower today than in 1998. No change in total column ozone may be due to increasing tropospheric ozone. State-of-the-art models do not reproduce lower stratospheric ozone decreases.
Final-revised paper