The state of scientific understanding regarding the ozone-depletion issue has advanced in recent years as a result of the concerted efforts of hundreds of scientists worldwide. Acknowledging this progress, the assessments are now focused on answering the question, "What's new regarding this issue that is of utmost relevance to the Parties to the Montreal Protocol?"
The most recent assessment (2010; the "green book"; 5 chapters) built upon the knowledge of the 2006 assessment (the "tan book"; 8 chapters) and focused on a few topics that were: (i) ones in which substantial advances had occurred (e.g., climate-ozone connections) and (ii) updated/new information requested by the Parties to the Montreal Protocol.
The 2014 assessment will continue in this tradition of updating the previous assessment in describing "what's new" and providing the Parties with information that they specifically requested for the 2014 report (see the Attachment A, Terms of Reference from Decision XXIII/13 of the Parties to the Montreal Protocol, Bali, Indonesia, November 2011). With regard to the second point, the 2014 assessment will have an increased emphasis on providing information in policy-relevant formats that are most conducive to use by decision-makers, such as the Parties to the Montreal Protocol. This is based on the feedback we have received from the Parties, the UNEP Ozone Secretariat, and others in the decision-making community. To accomplish this goal, we have made some changes to the approach used in past assessments.
Recognizing that the assessment is fundamentally driven by the needs of decision-makers and is produced in accordance with the terms of the Montreal Protocol, a new approach to publishing the assessment will be used for 2014 (see schematic below). In this approach, the assessment will have a component that is aimed specifically at meeting the needs of decision-makers. This component will be a short document, on the order of 30-40 pages including figures (plus appendices), focused on policy-relevant information and highlights, and written in a very understandable language to facilitate its use by the Parties and other decision-makers. This document will subsume–and add to–the material previously referred to as the "Executive Summary" of the assessment. It will be published both in printed form and on the Web. Detailed scientific chapters will still provide the scientific basis for the above document for decision-makers. As in the past, the chapters will be published on the Web; but unlike in the past, they will not be published in a printed book (following the path that most scientific journals now employ).
The above approach will have several advantages.
The 2014 assessment will use much of the same basic chapter structure that was used in the 2010 assessment (the "green book"). This will greatly simplify the early discussions of organizing chapter material, decisions on topic placement within the chapter structure, and cross-chapter coordination. This also allows us to focus on only what is new, without repeating what is in the green book. This simplification enables some of the changes in approach and schedule that are discussed below.
As described in the above overview, the assessment process will result in two components:
The Scientific Chapters (left side of schematic)
Information for the Decision-Making Community (right side of schematic)
This document will provide information that is specifically of interest to decision-makers, such as the Parties to the Montreal Protocol. Three major components are envisioned:
This document for the decision-making community will be drafted and reviewed by the Cochairs, Steering Committee, Lead Authors, Chapter Editors, and Les Diablerets panel reviewers. Because the Chapters form the scientific foundation for this document, the Chapters will be finalized earlier in the process than in past assessments (before Les Diablerets; see Timeline in Attachment C). The Panel Review meeting in Les Diablerets will be focused on producing the assessment for decision-making (right side of the schematic).
Chapter Team Structure
The 2014 ozone assessment chapters will return to the author structuring used in 2006 and earlier assessments, namely: two Lead Authors, Coauthors, and Contributors. The Coordinating Lead Author tier used in 2010 will not be used in 2014 (this is in response to feedback we received in 2010). New for 2014: Each chapter will have two Chapter Editors, who will ensure that review comments are adequately and appropriately dealt with, and will also help the Lead Authors coordinate with other chapters. Chapter Editors could also assist the Lead Authors in identifying policy-relevant information from the chapter.
Information from Other Assessments, Reports, and Publications
The 2014 ozone assessment will both draw from and build upon the findings of:
The 2014 assessment's chapter structure contains five chapters, paralleling much of the chapter structure of the 2010 assessment (with a recasting of Chapters 2 and 3, and with slight rewordings of the chapter titles in some cases):
Because the chapter material will be an update of the 2010 report, the cumulative sum of their pages will aim to be about half the sum total of the five chapters of the green book. Guidelines on number of pages and figures will be established for each of the chapters and strictly adhered to.
Chapter 1. Update on Ozone-Depleting Substances (ODSs) and Other Gases of Interest to the Montreal Protocol
Focus: Long-lived and short-lived substances that deplete the ozone layer (e.g., CFCs, HCFCs, methyl bromide) and other molecules of special interest to the Parties (e.g., HFCs, N2O, other recent substitutes, very short-lived substances). Major sections will address updated information on lifetimes, trends, and budgets, based on observations and models. The information will take into account, and draw from, the data and analyses in the 2010 ozone assessment and the AR5 report by the IPCC (early 2014), as well as the SPARC assessment on lifetimes of halogen source gases (November 2013). Updated information on the carbon tetrachloride budget is specifically requested by the Parties and will be included, as will information also requested by the Parties on the potential new ODS, R-316c. The chapter (via interactions with the Technology and Economics Assessment Panel) will provide emissions information used in Chapters 2, 3, and 4 (below) of this 2014 ozone assessment. Any special, hitherto unassessed issues related to degradation of ODSs will be discussed. A discussion of tropospheric OH will be included, considering its importance in determining the atmospheric lifetimes of ODSs and related gases. For short-lived substances, there will be two major emphases of the chapter: (i) the short-lived gases in the Protocol that are still significant contributors to ODS loading (e.g., methyl bromide); and (ii) any updates to the thinking developed in previous assessments regarding the "very" short-lived substances (atmospheric lifetimes of less than about 0.5 yr), for which the traditional concept of a single, emission geography-independent and time-independent Ozone Depletion Potential does not apply (see Attachment A, Terms of Reference from the Parties to the Montreal Protocol). The spatial and temporal dependences of ODPs, discussed in Chapter 5 of this 2014 ozone assessment, will be referenced. This chapter will no longer cover material related to carbon dioxide and only a limited update regarding methane, since the IPCC AR5 will provide a very recent and comprehensive update for that information.
Chapter 2. Update on Global Ozone: Past, Present, and Future
Focus: Updated status of the observations and understanding of global ozone and rationalization of the variance (all scales) of the observations, including the potential roles of climate change and other non-halogen effects; update on expected trends of future ozone based on model calculations. This chapter assesses the insights that are possible by analyzing a combination of different satellite and ground-based data sets and sondes, as well as the role of large-scale, longer-term dynamics in the ozone changes of the lower stratosphere. Observations of aerosols, and the possible influences of changes in aerosols as well as the solar cycle, are core information for this chapter. The chapter applies rigorous statistical methods in defining ozone changes. Discussion of causes of past ozone changes is also included in the chapter by the analysis of a range of model simulations (two- dimensional or 2-D and three-dimensional or 3-D).
This chapter also addresses the trends of future ozone based on recent model calculations. This is a key "closure" issue for the Montreal Protocol. This chapter addresses the question of how climate change will affect the evolution of the ozone layer and ozone-layer recovery, with emphasis on the mechanisms and key processes involved. Coupled chemistry-climate models (CCMs) will be used to elucidate and examine the mechanisms and processes. Two primary issues regarding the future ozone layer are (i) the detection and attribution of ozone recovery, and (ii) the projections of future ozone through the 21st century. CCMs would be used to explore several possible future developments relevant to the ozone layer, such as circulation acceleration in the tropical lower stratosphere. Potential influences such as volcanoes, geoengineering, and tropospheric composition changes (including emission scenarios) will be briefly included. Model predictions will include a discussion of uncertainties and potential for future surprises.
Chapter 3. Update on Polar Ozone: Past, Present, and Future
Focus: Polar ozone/temperature changes and processes; update on expected trends of future Arctic and Antarctic ozone and scientific understanding. The chapter includes a thorough update on the understanding of ozone trends and variability in the Arctic and Antarctic, building upon recent extensive observations, field studies, and theory. The Antarctic section additionally assesses recent changes and near-term expectations. Past assessments have underscored the fact that small year-to- year variability is expected (e.g., changes in vortex patterns and early formation and/or breakup) and, here, the overall picture for the persistence of the ozone hole for decades is explored. The 2011 Arctic ozone losses are briefly discussed in the context of long-term trends and expectations. The climatology of polar stratospheric clouds (PSCs) is discussed mainly in the context of the Arctic region. Our understanding of the observed ozone changes due to halogen loading, temperature changes, and dynamical processes is highlighted.
As with the Global Chapter 2, this chapter also updates the trends of future Arctic and Antarctic ozone based on most recent investigations using model calculations and scientific understanding. Because polar ozone losses are the most prominent effects of ODSs on our atmosphere, this is a key "closure" issue for the Montreal Protocol. This chapter addresses the question of how climate change will/will not affect the evolution of polar ozone and recovery, with emphasis on the mechanisms and key processes involved. CCMs are used to elucidate and examine the mechanisms and processes. Two primary issues regarding the polar ozone are (i) the detection of both Antarctic (ozone hole) and Arctic recovery, and (ii) assessment of future polar ozone levels through the 21st century. Potential influences such as volcanoes and geoengineering are briefly included. Model predictions include a discussion of uncertainties and potential for future surprises.
Chapter 4. Stratospheric Ozone Changes and Climate
Focus: The influence of stratospheric ozone changes on tropospheric and surface climate. The chapter discusses changes in stratospheric composition, as well as changes in stratospheric temperature and circulation. The effects of stratospheric ozone change on the tropospheric circulation are assessed, and the effects on surface climate, the ocean, sea ice, radiative forcing, and tropospheric chemistry are discussed. This chapter will also include the discussion of water vapor (including observations of its changes), stratospheric aerosols, and source gas changes in the context of stratospheric temperature trends. The chapter assesses the effects of future changes in stratospheric ozone on the troposphere.
Chapter 5. Scenarios, Information, and Options for Policymakers
Focus: Projected future behavior/scenarios of effective equivalent stratospheric chlorine (EESC). Future scenarios will be developed (via interaction with the Technology and Economic Assessment Panel) for emissions of controlled substances expected under the Protocol and other assumptions. The major characteristics of the future abundances will be explored (including the impact of revised lifetimes), and the differences among the scenarios could be quantified with respect to the estimated anthropogenic impact of ODSs on stratospheric ozone depletion. Updated (where needed) ODPs and GWPs will be included in the chapter. The chapter also will examine the implications of different policy approaches for the radiative forcing by HFCs and their potential replacements.
Attachment A. Request from the Parties to the Montreal Protocol
The following are the Terms of Reference for the Scientific Assessment Panel, from Decision XXIII/13 of the Parties to the Montreal Protocol:
"...that the 2014 report of the Scientific Assessment Panel should include:
Attachment B. Cochairs and Steering Committee of the Scientific Assessment Panel of the Montreal Protocol
Attachment C. Estimated Timetable
|Discussion Paper circulated for comments by scientific community||February 2013|
|Lead Authors and Chapter Editors established||early April|
|Chapter author teams assembled, early preparation steps begin||early May|
|Draft of Chapter outlines due||late May|
|First meeting of Lead Authors, Cochairs, Steering Committee, Chapter Editors (to discuss/plan first drafts)||10-11 June 2013; Cambridge, UK|
|Individual Chapter team meetings (convened by Lead Authors)||July-August-September|
|First drafts of Chapters completed||30 October 2013|
|Mail Review of Chapter first drafts||1 November to 10 December 2013|
|Second draft of Chapters completed||early March 2014|
|Second meeting of Lead Authors, Cochairs, Steering Committee, Chapter Editors, and other reviewers|
(to review Chapter second drafts, discuss mail review comments and responses, and finalize Chapter bullets)
|8-10 April 2014; Boulder, USA|
|Drafting of Assessment for Decision-Makers begins||early April|
|Final drafts of Chapters completed||mid May|
|Draft of Assessment for Decision-Makers distributed to Les Diablerets Panel Reviewers||early June|
|Panel Review Meeting (to discuss and finalize the Assessment for Decision-Makers)||23-27 June 2014; Les Diablerets, Switzerland|
|Assessment for Decision-Makers available on web||10 September 2014|
|Assessment for Decision-Makers printed, and Chapters available on web||December 2014|