Report of the Scientific Assessment Panel 24th Meeting of the Parties to the

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