The Working Group on Coupled Models (WGCM) Report to JSC, 2010

1. The Working Group on Coupled Models (WGCM) Report to JSC, 2010 Sandrine Bony & Jerry Meehl WGCM co-chairs Antalya, Feb 2010

2. WGCM Mission • Review and foster the development of coupled climate models (and now ESMs) • Coordinate model experiments and inter-comparisons to: - better understand natural climate variability - predict the climate response to natural & anthropogenic perturbations • Promote and facilitate model validation and diagnosis of shortcomings A balance between : Predicting – Evaluating - Understanding

3. Coordinated Model Experiments : CMIP3 : a big boost to climate science • More than 500 publications • More than 765 TB downloaded • More than 3,000 users Nov 2004 Jan 2007 (AR4 WGI) Aug 2009 Courtesy of Bob Drach & Karl Taylor, PCMDI

4. From CMIP3 to CMIP5 : What should be improved ? • Better inform decisions on climate change adaptation and mitigation • Integrate Earth System Modelling • Better assess robust and uncertain aspects of climate change • Facilitate model evaluation and assess confidence in model projections + improvements on the infrastructure side … this led to CMIP5

5. CMIP5 : a framework for climate change modeling over the next 5+ years • Promotes a standard set of model simulations in order to : • evaluate how realistic the models are in simulating the recent past • provide projections of future climate change on two time scales • understand some of the factors responsible for model differences • Two timescales and two sets of science problems • Will be assessed by the IPCC AR5 • Taylor et al. 2009, http://cmip-pcmdi.llnl.gov/cmip5/ Long-Term : (past to 2100 & beyond) → evaluation of climate models (recent past, A-Train, paleo) → detection & attribution → climate change scenarios → climate sensitivity, radiative forcing and physical feedbacks (e.g. clouds) → biogeochemical feedbacks (e.g. carbon, chemistry) Near-Term : (next 3-4 decades) → decadal climate predictability → ocean initialization → impact volcanos → regional climate changes (high resol) & climate extremes → air quality changes (aerosols, chemistry)

6. CMIP5 : a framework for climate change modeling over the next 5+ years • Promotes a standard set of model simulations in order to : • evaluate how realistic the models are in simulating the recent past • provide projections of future climate change on two time scales • understand some of the factors responsible for model differences • Two timescales and two sets of science problems • Will be assessed by the IPCC AR5 • Taylor et al. 2009, http://cmip-pcmdi.llnl.gov/cmip5/ For computationally demanding models : very high resolution or very complex models, or new generation of climate models (MMF, global CRMs) : Prescribed SST time-slices (1979-2008 + 2026-2035) + idealized experiments (e.g. aqua-planet, +4K, 4xCO2) → regional effects of climate change → explore the impact of higher resolution on climate simulations : mean & variability, extremes, AND sensitivity to external perturbations. AMIP CORE “time-slice”

7. Model Evaluation Climate Projections individual forcing ensembles: AMIP & 20 C D & A ensembles extend RCP8.5 & RCP2.X to 2300 RCP2.X, RCP6 natural-only, GHG-only Control, AMIP, & 20 C RCP4.5, RCP8.5 extend RCP4.5 to 2300 lastmillennium Mid-Holocene & LGM E-driven control & 20 C E-driven RCP8.5 aqua planet (clouds) 1%/yr CO2 (140 yrs) abrupt 4XCO2 (150 yrs) fixed SST with 1x & 4xCO2 ensemble of abrupt 4xCO2 5-yr runs patterned ΔSST (clouds) aerosol forcing ca. 2000 unform ΔSST (clouds) radiation code sees 1xCO2 (1% or 20C+RCP4.5) AC&C4 (chemistry) carbon cycle sees 1XCO2 (1% or 20C+RCP4.5) Understanding An important focus put on model evaluation and understanding... Example of CMIP5 Long-Term Experiments All simulations are forced by prescribed concentrations except those “E-driven” (i.e., emission-driven). Coupled carbon-cycle climate models only

8. ... In collaboration with many WCRP/IGBP partners Example of CMIP5 Long-Term Experiments Detection-Attribution (IDAG) Integrated Assessment Consortium (IAM), connection to WG-III Paleo (PMIP, IGBP-PAGES) + Satellite simulators & process diagnostics (CFMIP-GCSS) Cloud and moist processes (CFMIP-GCSS WGNE) Chemistry, aerosols (SPARC, AC&C) Carbon-climate feedbacks (C4MIP, IGBP-AIMES)

9. Status and Timeline : • At least 21 global modeling groups will participate in CMIP5. Likely that about 5 groups will have 50 km class AOGCMs for decadal prediction, at least 10 groups will have ESMs, several groups will have high-resolution AGCMs (<50 km). • The full sets of forcings and boundary conditions, and the list of model outputs, have been finalized. • Simulations have now started in many modeling groups. • Model outputs will be archived on the “Earth System Grid” (distributed grid technology) which is being deployed and tested now. • An extensive documentation of the models and of model experiments will be available for CMIP5 through EU Metafor (standardized vocabulary and documentation), and US Earth System Curator projects (web-based tools for ingesting metadata). • PCMDI will require agreement to the “terms of use” as part of the registration procedure. CMIP data will be divided into two classes: unrestricted and restricted-use (no restriction: 7 out of 12). • Analyses of model data will begin late 2010, and will be assessed by the IPCC AR5. • CMIP5 model simulations and analyses will continue well beyond AR5 deadlines.

10. In parallel to CMIP5, many other climate model coordinated experiments are being organized by the modelling community • WGCM (PMIP, CFMIP..): paleo, clouds • WGNE/WGCM (Transpose-AMIP): evaluation of climate models in NWP mode - CLIVAR WGSIP, WGOMD : seasonal to interannual prediction, ocean • TFRCD (CORDEX) : regional • GEWEX GCSS (GPCI) : processes • SPARC & IGBP/IGAC (CCMVal, AeroCom..): chemistry & aerosols • IGBP/AIMES (C4MIP) : carbon feedbacks • … and much more! + WGNE/WGCM Metrics panel

11. Proposal for coordinated geo-engineering experiments with stratospheric aerosols by Ben Kravitz, Alan Robock et al. Aim: explore the efficacy and risks of stratospheric geo-engineering with sulfate aerosols. Demonstration project to be conducted by a few modeling groups. Coordination with SPARC? Not part of CMIP5. Received some feedback from WGCM last September. Issues of particular interest : - robustness of the model responses to geo-engineering - response of the hydrological cycle, temperature patterns and stratospheric ozone - response to the stoppage of geoengineering after a few decades Several experiments proposed for coupled ocean-atmosphere models including interactive aerosols and chemistry : - in combination of 1% increase CO2 per year, progressively balance the CO2 radiative forcing by a reduction of the solar constant - in combination of RCP 4.5 scenario: progressively balance the CO2 radiative forcing by injecting stratospheric aerosols (or SO2) at the equator. - abrupt stoppage of geo-engineering after 50 years + simpler idealized experiments to better understand inter-model differences Interested modeling groups will perform these experiments this year. More groups might join after this demonstration project. How should this be coordinated across WCRP?

12. BIG CHALLENGE : How to improve our confidence in climate models ? How to assess the credibility of model projections ?

13. How to gain confidence in GCMs projections ? (1) Bottom-Up approach : evaluate and improve the physical basis of climate models through large-scale and process-scale evaluations High resolution global models (global CRM, MMF) Model projections LES models Cloud Resolving Models Single Column Models 3D-Climate Models NWP Models Analysis & Understanding climate change Field campaigns & instrumented sites Global observational datasets

14. How to gain confidence in GCMs projections ? (1) Bottom-Up approach : evaluate and improve the physical basis of climate models through large-scale and process-scale evaluations (2) Top-Down approach : understand the models' results & identify critical processes to provide guidance for specific observational tests/process studies and model improvements High resolution global models (global CRM, MMF) Model projections LES models Cloud Resolving Models Single Column Models 3D-Climate Models NWP Models Analysis & Understanding climate change Field campaigns & instrumented sites Global observational datasets

15. CMIP5 and associated modeling activities : an opportunity to develop both approaches, especially the second one - Better interpret inter-model differences in current climate & climate projections - Evaluate climate models over a wide range of scales and phenomena i.e. from weather to paleo time scales, from regional to global, from processes to climate, across all physical and biogeochemical components - Explore how model formulation and present-day model performance translate to reliability of climate projections → a big challenge and a key focus of WGCM activities over the next few years, in collaboration with WCRP/IGBP partners

16. A WGCM project supported by WCRP/CLIVAR and IGBP/PAGES Coordinated by: P. Braconnot & S. Harrison with S. Joussaume, B. Otto-Bliesner, A. Abe-Ouchi, A. Haywood, P. Valdes, G.Ramstein, K. Taylor, P. Bartlein, M. Kucera, J. Jungclaus • Main objectives: Coordinate paleoclimate modelling activities to : - Understand the mechanisms of past climate change - Test whether climate models can represent a climate state different from the present-day

17. PMIP – Phase 3 • Coordinated model experiments : • PMIP3 / CMIP5 simulations : - Mid-Holocene (6 ka) - Last Glacial Maximum (LGM, 21 ka) - Last Millenium → using the same model version than for CMIP5 simulations of present-day and climate projections ! • Data syntheses : • Key periods • Assess uncertainties in past reconstructions e.g. Reconstructed SST anomalies at LGM MARGO: Nature Geoscience 2009 PMIP database and website : http://pmip2.lsce.ipsl.fr (Taylor et al. 2009) → PMIP working groups also focus on other key periods (e.g. last inter-glacial 130 ka, Mid-Pliocene 3 Myr ago, etc)

18. Laîné et al. 2009 Constraints on climate sensitivity Temperature response over different ocean basins at LGM : • + data • models Otto-Bliesner et al. 2009 Polar amplification : Continental vs ocean response : Masson-Delmotte et al, 2005

19. Constraints on the response of the hydrological cycle Change in precipitation inferred for Mid-Holocene (6 ka) over western Africa : Joussaume et al. 1999 Braconnot et al. 2007

20. Cloud Feedback Model Inter-comparison Project Phase-2 CFMIP-2 (www.cfmip.net) Building bridges through the cloud communities A WGCM project coordinated by : Mark Webb, Sandrine Bony, Christopher Bretherton, Steve Klein, George Tselioudis Aims : Encourage coordinated research in the area of cloud-climate feedbacks. Facilitate the evaluation of clouds simulated by climate models Strong interactions between climate/process/observation/NWP communities

21. Cloud Feedback Model Inter-comparison Project Phase-2 CFMIP-2 (www.cfmip.net) Understanding Evaluation Assessment of cloud-climate feedbacks

22. Cloud Feedback Model Inter-comparison Project Phase-2 CFMIP-2 (www.cfmip.net) Understanding Evaluation GCM analysis through a hierarchy of models Assessment of cloud-climate feedbacks

23. Cloud Feedback Model Inter-comparison Project Phase-2 CFMIP-2 (www.cfmip.net) Understanding Evaluation GCM analysis through a hierarchy of models Process studies (in-situ obs, LES/CRMs) Assessment of cloud-climate feedbacks

24. CFMIP/GCSS/CMIP5 model outputs at selected locations (118 locations, high-frequency, detailed cloud diagnostics) SHEBA Barrow Chibolton SIRTA Oklahoma Tibet GPCI ASTEX AMMA RICO TOGA-COARE GATE Darwin VOCALS • ARM, CEOP, CloudNet instrumented sites • GPCI / Tropical West & South East Pacific / AMMA transects • Field experiments / GCSS case studies • Locations of large inter-model spread of cloud feedbacks (CMIP3)

25. CFMIP-GCSS Study of Cloud Feedback Mechanisms by using SCM/CRM/LES Models (CGILS, coordinated by Minghua Zhang) Case studies of PBL cloud feedback mechanisms

26. Cloud Feedback Model Inter-comparison Project Phase-2 CFMIP-2 (www.cfmip.net) Understanding Evaluation GCM analysis through a hierarchy of models Process studies (in-situ obs, LES/CRMs) Satellite observations & simulators (COSP) Assessment of cloud-climate feedbacks

27. Cloud Vertical Distribution CALIPSO-GOCCP ECHAM5 + SIM CAM3.5 + SIM OBS 0.3 CCCMA + SIM LMDZ4 + SIM • Overestimate: • of high clouds • Underestimate of: • Tropical low clouds • Congestus clouds • extratropical mid-level clouds 0 Chepfer et al. (Calipso-Cloudsat workshop, Jul 2009)

28. Vertical distributions of radar reflectivities (CFADs) CloudSat (Bodas-Salcedo et al., in preparation)

29. Link available from www.cfmip.net Observations useful for the evaluation of model clouds through COSP

30. Observations for CMIP5 Simulations • The climate modeling community would greatly benefit from an easier and more coordinated access to observations for model evaluation and analysis. • Many individual initiatives worldwide (different MIPs, ARM, etc) CMIP5 might be an excellent opportunity to foster a coordinated access to observations that are most useful for model evaluation. • Recently, JPL (Joao Texeira, Duane Waliser, Jerry Potter, S Boland) launched such an initiative - To provide the community of researchers that will analyze CMIP5 simulations access to analogous sets of observational data. - Analogous sets in terms of periods, variables, temporal/spatial frequency - This activity will be carried out in close coordination with CMIP5 & modelling activities - It will directly engage the observational (e.g. mission and instrument) science teams to facilitate production of the corresponding data sets. Discussions already engaged with NASA. What about other providers of satellite and in-situ observations? To be discussed with WOAP and GCOS.

31. Conclusion Trying to keep the balance between predicting, evaluating and understanding... CMIP5 : - many new features : decadal, ESMs, high-resolution, satellite and process outputs.. - strong partnership with WCRP partners and IGBP (joint WGCM-AIMES meeting) - huge effort for modeling groups and many other communities Analysis of CMIP5 simulations : an opportunity to - build connections among modeling communities and between modeling, processes and observation - address key science challenges e.g. assessing the reliability of model projections based on model evaluation at different time scales. cf IPCC expert meeting on multi-model simulations - help interpret model deficiencies and guide the model development process (motivation for the Survey on model evaluation and improvement at last CLIVAR SSG). Issues for JSC : - coordination of observations for model evaluation (modeling – WOAP – GCOS panels) - coordination & syntheses of different MIPs, evaluations and analyses across WCRP & IGBP - CMIP5 analysis : recommendations? e.g. encourage coordinated analyses and syntheses about key topics cross-acronyms (strengthen connections + help AR5 authors)

32. WCRP-WWRP-THORPEX Consultation on Model Evaluation and Improvement Sandrine Bony, Jerry Meehl, Anna Pirani (WGCM) Christian Jakob, Martin Miller (WGNE) Ben Kirtman (WGSIP), Stephen Griffies (WGOMD), Tony Busalacchi (WCRP) Background and Goal : - Model errors and biases are key limitations of the skill of model predictions over a wide range of time and space scales ; - Not a new story. The increase of resolution and the addition of complexity in ESMs have not solved the problem. - How to tackle the problem ? What should we do? What can we do ? -> Bottom-up consultation of NWP/climate modeling groups, CLIVAR WGs/panels, WCRP/WWRP/IGBP projects - Restructuration of WCRP : an opportunity to put recommendations into action. More in a few minutes....