SPARC CCMVal Report: Outline

SPARC CCMVal Report: Draft Outline

11 July 2007

Draft Outline for SPARC Report on Evaluation of Chemistry Climate Models (CCMVal)
Steering Committee:     Veronika Eyring, Ted Shepherd & Darryn Waugh

N.B. This outline has been prepared by the Steering Committee with some input from the SPARC SSG.

Chemistry climate models (CCMs) representing the stratospheric ozone layer are key tools for the detection, attribution and, especially, prediction of the response of stratospheric ozone to ozone-depleting substances and other factors (climate change, solar variability, volcanic eruptions, natural variability). It is therefore necessary to quantitatively assess the confidence that can be placed in the CCMs. The present report responds to this need by providing a comprehensive, up-to-date assessment of the ability of CCMs to represent the stratospheric ozone layer, stratospheric climate and climate variability, and the coupled ozone-climate response to natural and anthropogenic forcings. The assessment will be based on the diagnostic metrics developed within the SPARC CCMVal project (see http://www.pa.op.dlr.de/CCMVal/CCMVal_EvaluationTable.html), and will be completed in time to provide useful and timely information for the expected 2010 WMO/UNEP Ozone Assessment, as well as for the expected IPCC AR5. Publication of the material included in the SPARC report in the open literature is encouraged. As SPARC reports are peer-reviewed documents the only requirement is that associated publications need to be submitted before the SPARC report is published. Compared to the individual publications the SPARC report will allow the inclusion of a lot more detail and provide a coherent, integrated assessment of the CCMs based on the CCMVal concept. The report will consider all available runs (i.e. REF1/REF2/SCN2 runs for the 2006 WMO/UNEP Ozone Assessment, new assessment runs, and any other runs as appropriate).

Executive Summary
ALL; to be written at the final plenary review meeting

The executive summary will be divided into overall key findings, key findings per chapter, and key findings for each of the participating models. The key findings per chapter in Part A will be based on the models’ ability to simulate core processes structured around five major topics (radiation, dynamics, transport, stratospheric chemistry & microphysics, and UTLS). The overall key findings will include a synthesis of the results presented in the five topics to provide a coherent assessment of the current generation of CCMs based on the CCMVal concept. It will also include a summary of the results presented in Part B. The processes that contribute most to uncertainty in current coupled chemistry-climate modeling will be defined and future challenges for model developments summarized. The key findings per model will summarize the performance of each of the participating models relative to the thresholds identified in the individual chapters.

1. Introduction
Steering Committee

Chapter 1 will provide a contextual background to CCMVal and the role of CCMs in previous assessments, and describe the purpose of the report. This will include a very brief discussion of the coupling between stratospheric ozone and climate and the key science questions that are involved. The chapter will also motivate and provide a road map to the structure of the report.

2. Chemistry climate models and scenarios
Lead Authors: Marco Giorgetta & Kiyotaka Shibata

Chapter 2 will describe the basic ingredients in CCMs, in terms of theoretical fundamentals, and their key approximations and uncertainties. This discussion will need to address the question of what is required of a CCM, in terms of its basic set-up, in order to be considered for the science topics addressed by this assessment — a topic to be resolved at the 2007 CCMVal Workshop in Leeds. Chapter 2 will also provide a detailed model documentation of the participating CCMs, which can be based on a questionnaire to be sent to all participating CCM groups with detailed questions on, e.g., the underlying AGCM, the chemistry module, the transport scheme, and coupling interfaces. Some of this documentation information is already provided in Eyring et al. (2006, 2007), but will need to be extended and updated. Finally, Chapter 2 will describe the forcing scenarios used for the runs to be analyzed, and why they were chosen.

Part A: Process evaluation

The chapters in Part A will evaluate how well the CCMs do according to the CCMVal diagnostics tables, under present-day conditions. Each process is associated with one or more model diagnostics and with relevant datasets that can be used for model evaluation. This approach provides a coherent framework for the evaluation of CCMs and will be used as a basis for the assessment of long-term changes in Part B. Motivated by Chapter 2, the processes that contribute most to uncertainty in each of the chapters will be defined. The chapters in Part A should include all diagnostics of the CCMVal evaluation table, with the exception of those considered under Chapter 8, as well as any additional diagnostics the authors might wish to include. As there is no separate list of UTLS diagnostics in the diagnostic tables, the UTLS chapter will draw on the relevant diagnostics from the other tables. For the REF1 and REF2 runs performed for the 2006 Ozone Assessment, some, but not all, of these diagnostics have already been produced and assessed in Eyring et al. (2006). In addition the chapters in Part A will include long-term changes of the key processes in the past and future (e.g changes in Brewer-Dobson circulation, PSC frequency, mean age of air, transport barriers, sudden warmings, water vapor budget in the UTLS, etc.).

3. Radiation
Lead Authors: Victor Fomichev & Piers Forster

4. Dynamics
Lead Authors: Neal Butchart & Andrew Charlton

5. Transport
Lead Authors: Jessica Neu & Susan Strahan

6. Stratospheric Chemistry & Microphysics
Lead Authors: Martyn Chipperfield & Doug Kinnison

7. UTLS
Lead Authors: Andrew Gettelman & Michaela Hegglin

Part B: Chemistry-climate coupling

8. Natural variability
Lead Authors: Elisa Manzini & Katja Matthes

Chapter 8 will evaluate how well CCMs represent the effects of various sources of coherent forced and unforced natural variability (QBO, volcanic, solar, ENSO) on stratospheric dynamics, radiation, chemistry and transport. Some relevant diagnostics are included in the CCMVal evaluation table, and many CCMVal Collaborator projects will contribute to this chapter.

9. Long-term projections of stratospheric ozone
Lead Authors: John Austin & John Scinocca

Chapter 9 will focus on long-term changes (past and future) in ozone and ozone indices and on the cause of these changes (i.e. relate to changes in chemistry, dynamics, radiation, transport and UTLS discussed in Part A chapters). For the REF1 and REF2 runs performed for the 2006 Ozone Assessment, this has already been done by Eyring et al. (2006, 2007), though some more details concerning those results could be usefully provided here. The main work for this chapter will involve evaluating the behavior of ozone recovery in the new runs that will be performed for the 2010 Ozone Assessment.

10. Effect of the stratosphere on climate
Lead Authors: Mark Baldwin & Nathan Gillett

Chapter 10 will evaluate the impact of stratospheric changes on the troposphere. This will include the radiative forcing from ozone changes, tropospheric effects of polar ozone depletion, and changes in the flux of ozone to the troposphere over long timescales (past and future). Many of the CCMVal diagnostics can be used to address these questions, and many CCMVal Collaborator projects will contribute to this chapter. This chapter should specifically target the needs of the next IPCC report.