Scientific Assessment of Ozone Depletion: 2010


2010 Ozone Assessment cover

The present document will be part of the information upon which the Parties to the United Nations Montreal Protocol will base their future decisions regarding protection of the stratospheric ozone layer.

The Charge to the Assessment Panels

Specifically, the Montreal Protocol on Substances that Deplete the Ozone Layer states (Article 6): ". . . the Parties shall assess the control measures . . . on the basis of available scientific, environmental, technical, and economic information." To provide the mechanisms whereby these assessments are conducted, the Protocol further states: ". . . the Parties shall convene appropriate panels of experts" and "the panels will report their conclusions . . . to the Parties."

To meet this request, the Scientific Assessment Panel, the Environmental Effects Assessment Panel, and the Technology and Economic Assessment Panel have each prepared, about every 3-4 years, major assessment reports that updated the state of understanding in their purviews. These reports have been scheduled so as to be available to the Parties in advance of their meetings at which they will consider the need to amend or adjust the Protocol.

The Sequence of Scientific Assessments

The present 2010 report is the latest in a series of eleven scientific assessments prepared by the world's leading experts in the atmospheric sciences and under the international auspices of the World Meteorological Organization (WMO) and/or the United Nations Environment Programme (UNEP). This report is the seventh in the set of major assessments that have been prepared by the Scientific Assessment Panel directly as input to the Montreal Protocol process. The chronology of all the scientific assessments on the understanding of ozone depletion and their relation to the international policy process is summarized as follows:

YearPolicy ProcessScientific Assessment
1981The Stratosphere 1981 Theory and Measurements. WMO No. 11.
1985Vienna ConventionAtmospheric Ozone 1985. Three volumes. WMO No. 16.
1987Montreal Protocol
1988International Ozone Trends Panel Report 1988. Two volumes. WMO No. 18.
1989Scientific Assessment of Stratospheric Ozone: 1989. Two volumes. WMO No. 20.
1990London Adjustments and Amendment
1991Scientific Assessment of Ozone Depletion: 1991. WMO No. 25.
1992Methyl Bromide: Its Atmospheric Science, Technology, and Economics (Assessment Supplement). UNEP (1992).
1992Copenhagen Adjustments and Amendment
1994Scientific Assessment of Ozone Depletion: 1994. WMO No. 37.
1995Vienna Adjustment
1997Montreal Adjustments and Amendment
1998Scientific Assessment of Ozone Depletion: 1998. WMO No. 44.
1999Beijing Amendment
2002Scientific Assessment of Ozone Depletion: 2002. WMO No. 47
2006Scientific Assessment of Ozone Depletion: 2006. WMO No. 50
2007Montreal Adjustment
2010Scientific Assessment of Ozone Depletion: 2010. WMO No. 52
201123rd Meeting of the Parties

The Current Information Needs of the Parties

The genesis of Scientific Assessment of Ozone Depletion: 2010 occurred at the 19th Meeting of the Parties to the Montreal Protocol in Montreal, Canada, at which the scope of the scientific needs of the Parties was defined in their Decision XIX/20 (4), which stated that "...for the 2010 report, the Scientific Assessment Panel should consider issues including:

  1. Assessment of the state of the ozone layer and its future evolution;
  2. Evaluation of the Antarctic ozone hole and Arctic ozone depletion and the predicted changes in these phenomena;
  3. Evaluation of the trends in the concentration of ozone-depleting substances in the atmosphere and their consistency with reported production and consumption of ozone-depleting substances and the likely implications for the state of the ozone layer;
  4. Assessment of the interaction between climate change and changes on the ozone-layer;
  5. Assessment of the interaction between tropospheric and stratospheric ozone;
  6. Description and interpretation of the observed changes in global and polar ozone and in ultraviolet radiation, as well as set future projections and scenarios for those variables, taking into account among other things the expected impacts of climate change;
  7. Assessment of consistent approaches to evaluating the impact of very short-lived substances, including potential replacements, on the ozone layer;
  8. Identification and reporting, as appropriate, on any other threats to the ozone layer..."

The 2010 assessment has addressed all the issues that were feasible to address to the best possible extent.

The Assessment Process

The formal planning of the current assessment was started early in 2009. The Cochairs considered suggestions from the Parties regarding experts from their countries who could participate in the process. Furthermore, an ad hoc international scientific advisory group also suggested participants from the world scientific community. In addition, this advisory group contributed to crafting the outline of the assessment report. As in previous assessments, the participants represented experts from the developed and developing world. The developing country experts bring a special perspective to the process, and their involvement in the process has also contributed to capacity building.

The information of the 2010 assessment is contained in five chapters associated with ozone-layer topics, which are preceded by a Prologue:

Prologue. State of the Science through the 2006 WMO/UNEP Assessment

Chapter 1. Ozone-Depleting Substances (ODSs) and Related Chemicals

Chapter 2. Stratospheric Ozone and Surface Ultraviolet Radiation

Chapter 3. Future Ozone and Its Impact on Surface UV

Chapter 4. Stratospheric Changes and Climate

Chapter 5. A Focus on Information and Options for Policymakers

The initial plans for the chapters of the 2010 Scientific Assessment Panel's report were examined at a meeting that occurred on 24-25 June 2009 in London, England. The Coordinating Lead Authors and Cochairs focused on the content of the draft chapters and on the need for coordination among the chapters.

The first drafts of the chapters were examined at a meeting that occurred on 17-19 November 2009 in Fairfax, Virginia, United States, at which the Coordinating Lead Authors, Cochairs, and a small group of international experts focused on the scientific content of the draft chapters.

The second drafts of the chapters were reviewed by 122 scientists worldwide in a mail peer review. Those comments were considered by the authors. At a Panel Review Meeting in Les Diablerets, Switzerland, held on 28 June-2 July 2010, the responses to these mail review comments were proposed by the authors and discussed by the 74 participants. Final changes to the chapters were decided upon at this meeting. The Executive Summary contained herein (and posted on the UNEP web site on 16 September 2010) was prepared and completed by the attendees of the Les Diablerets meeting. A small science advisory group assisted the Cochairs during those Les Diablerets discussions of the Executive Summary, and also helped with advance preparations during a meeting in Toronto on 17-18 May 2010.

The 2010 State-of-Understanding Report

In addition to the scientific chapters and the Executive Summary, the assessment also updates the 2006 assessment report's answers to a set of questions that are frequently asked about the ozone layer. Based upon the scientific understanding represented by the assessments, answers to these frequently asked questions were prepared, with different readerships in mind, e.g., students and the general public. These updated questions and answers are included in this report and published separately in a companion booklet to this report.

The final result of this two-year endeavor is the present assessment report. As the accompanying list indicates, the Scientific Assessment of Ozone Depletion: 2010 is the product of 312 scientists from 39 countries of the developed and developing world who contributed to its preparation and review[1] (191 scientists prepared the report and 196 scientists participated in the peer review process).

What follows is a summary of their current understanding of the stratospheric ozone layer and its relation to humankind.

[1] International Authors, Contributors, and Reviewers participating were Argentina, Australia, Belgium, Benin, Canada, Chile, Comores, Costa Rica, Czech Republic, Denmark, Egypt, Estonia, Finland, France, Germany, Greece, Hungary, India, Indonesia, Iran, Italy, Japan, Kenya, Malaysia, Mexico, New Zealand, Norway, Poland, Russia, Saudi Arabia, South Africa, Spain, Sweden, Switzerland, The Netherlands, The People's Republic of China, Togo, United Kingdom, and United States of America.