Scientific Assessment Panel Report for Ozone Protection

1. Report of the Scientific Assessment Panel 24th Meeting of the Parties to the United Nations Montreal Protocol 12-16 November 2012 Geneva, Switzerland Cochairs: Ayité-Lo Ajavon (Togo) Paul A. Newman (USA) John A. Pyle (UK) A.R. Ravishankara (USA) • Today’s Summary: • status of the 2014 report of the Scientific Assessment Panel • summary on carbon tetrachloride issues • summary on new compound R316c

2. The 2014 Science Assessment • November 2011: Parties define terms of reference • (23rd MOP [Bali], Decision XXIII/13) • Fall 2012: Preparatory work begins • October meeting of SAP Cochairs in Paris • Communication from SAP Cochairs and UNEP to the Parties, seeking nominations of participants • Replies requested by December 19 • Previous participants need not be renominated; they will be considered again • Replies to be sent to UNEP contact: Meg.Seki@unep.org

3. The 2014 Science Assessment Science topics to be addressed (Decision XXIII/13): • assess the state of the ozone layer and its future evolution (including, e.g., effects of sudden stratospheric warmings, or Brewer-Dobson circulation changes) • evaluate recent Antarctic ozone hole and Arctic ozone depletion behavior and predicted changes (especially focus on temperatures of the polar stratosphere) • evaluate trends of ozone-depleting substances in the atmosphere and their consistency with reported production and consumption • assess the interaction between the ozone layer and the atmosphere (esp. polar ozone depletion/tropospheric climate, ocean/atmosphere coupling) • describe ozone and surface ultraviolet radiation observations, and future expectations • further assessment of effects of ODSs and ozone-relevant substances, if any • identification of any other threats to the ozone layer

4. The 2014 Science Assessment • Our Coming Steps: • Parties to nominate experts to be authors or reviewers (by December 19, 2012) • Co-chairs solicit comments from scientific community on draft Chapter structure, author suggestions • Finalize Chapter structure, Chapter Leads • Chapter Teams form, Chapter preparation begins • Lead Author meeting to discuss Chapter outlines • Lead Author meeting to review Chapter first drafts • Mail review, in-person review (Le Diableret, CH), final Exec. summary in 2014 • Publication of assessment report in 2015 2012 2013 Nov-Dec ’12 Parties’ Nomination of Experts Dec ’12/Jan ’13 Determine Chapter Structure and Leads Feb-Oct ’13 Form Chapter Teams Prepare Chapter First Draft Nov/Dec ’13 Lead Author Meeting, First Draft Review

5. Summary of new information on carbon tetrachloride (CCl4) • A revision of the lifetime will reduce the “top-down” emission estimate by approximately 10-20 Gg/yr. • Estimates of global emissions from contaminated sites and landfills are approximately 8-12 Gg/yr, revising upward the “bottom-up” emission estimate. • The 40 Gg/yr emission budget gap between the “top-down” and “bottom-up” estimates has been narrowed, but not quite closed. • The simple assumptions made in WMO/UNEP (2011) to estimate fugitive emissions suggest that those emissions alone cannot explain the 40 Gg/yr budget gap.

6. Summary of information on chlorofluorocarbon: R-316c (C4F6Cl2) • Mainly photolyzed in the stratosphere by solar UV radiation • Lifetime of 81 years • A potent ODS with an ODP of approximately 0.5 • A powerful greenhouse gas with a 100-y GWP of 4300

7. SAP report summary • Preparatory work for the “Scientific Assessment of Ozone Depletion: 2014” has begun. The SAP co-chairs request that the Parties nominate expert participants. • The carbon tetrachloride emissions budget gap has been narrowed, but not quite closed. • The RC-316c is both a powerful ODS and greenhouse gas