US CLIVAR Summit 2009 US CLIVAR Decadal Predictability Working Group Report Co-Chairs: Lisa Goddard -- IRI, The Earth Institute of Columbia University Amy Solomon -- CIRES/University of Colorado & NOAA/ESRL Arun Kumar -- NOAA/Climate Prediction Center Co-Chairs: Lisa Goddard -- IRI, The Earth Institute of Columbia University Amy Solomon -- CIRES/University of Colorado & NOAA/ESRL Arun Kumar -- NOAA/Climate Prediction Center

US CLIVAR Summit 2009 US CLIVAR Decadal Predictability Working Group Formally approved January 2009 Objective 1: To define a framework to distinguish natural variability from anthropogenically forced variability on decadal time scales for the purpose of assessing predictability of decadal-scale climate variations. Objective 2: Work towards better understanding of decadal variability and predictability through metrics that can be used as a strategy to assess and validate decadal climate prediction simulations.

US CLIVAR Summit 2009 Membership US Membership: Jim Carton (University of Maryland) Tom Delworth (NOAA/GFDL) Clara Deser (NCAR) Ichiro Fukumori (JPL/NASA) Lisa Goddard (IRI/Columbia University) Ben Kirtman (University of Miami) Arun Kumar (NOAA/CPC) Yochanan Kushnir (Columbia University) Matt Newman (CIRES/NOAA) Amy Solomon (CIRES/NOAA) Dan Vimont (University of Wisconsin) Ex-officio Members: Arthur Greene (IRI/Columbia University) Gabi Hegerl (University of Edinburgh) Jerry Meehl - representing WGCM (NCAR) Doug Smith (UK Met Office) Tim Stockdale - representing WGSIP (ECMWF) US Membership: Jim Carton (University of Maryland) Tom Delworth (NOAA/GFDL) Clara Deser (NCAR) Ichiro Fukumori (JPL/NASA) Lisa Goddard (IRI/Columbia University) Ben Kirtman (University of Miami) Arun Kumar (NOAA/CPC) Yochanan Kushnir (Columbia University) Matt Newman (CIRES/NOAA) Amy Solomon (CIRES/NOAA) Dan Vimont (University of Wisconsin) Ex-officio Members: Arthur Greene (IRI/Columbia University) Gabi Hegerl (University of Edinburgh) Jerry Meehl - representing WGCM (NCAR) Doug Smith (UK Met Office) Tim Stockdale - representing WGSIP (ECMWF)

US CLIVAR Summit 2009 Scientific Focus of Telecons 1: How best to separate natural decadal variability from anthropogenically forced decadal variations? (Kushnir 2009)

US CLIVAR Summit 2009 Scientific Focus of Telecons 2: How do we address the issue of potential projection and interaction between the natural and forced variability? The mid-1970s climate shift in the Pacific was likely a combination of internally generated decadal variability and a forced response Forced response (~25%) Inherent decadal (~50%) Inherent and forced (~25% each) (Meehl, Hu, and Santer, 2009: The mid-1970s climate shift in the Pacific and the relative roles of forced versus inherent decadal variability, J. Climate, 22, )

US CLIVAR Summit 2009 Scientific Focus of Telecons 3) Do we have robust estimates of observed (or simulated) trends? Southern Annular Mode Monthly Trends (Deser 2009) Dots: Individual Ensemble Members Line: Ensemble Mean

US CLIVAR Summit 2009 Timeline June 2009: 1st Group Meeting and Session on “Advances in Decadal Climate Prediction” at the CCSM Workshop in Breckenridge, CO. Fall 2009: Submit white paper on “What additional skill we can expect from the initialized decadal predictions, and why?” Winter 2009/10: Group Meeting? (RSMAS Wrkshp) Spring 2010(?): Announcement of Opportunity by funding agencies for small grants to investigate decadal predictability in the AR5 initialized decadal climate projections Fall 2010: Group Meeting? (WGOMD Mtg) Spring 2011: Meeting on “Defining Metrics Relevant to Dynamical Decadal Predictions” Summer 2011: Write workshop report and WG wrap-up focused on decadal prediction metrics June 2009: 1st Group Meeting and Session on “Advances in Decadal Climate Prediction” at the CCSM Workshop in Breckenridge, CO. Fall 2009: Submit white paper on “What additional skill we can expect from the initialized decadal predictions, and why?” Winter 2009/10: Group Meeting? (RSMAS Wrkshp) Spring 2010(?): Announcement of Opportunity by funding agencies for small grants to investigate decadal predictability in the AR5 initialized decadal climate projections Fall 2010: Group Meeting? (WGOMD Mtg) Spring 2011: Meeting on “Defining Metrics Relevant to Dynamical Decadal Predictions” Summer 2011: Write workshop report and WG wrap-up focused on decadal prediction metrics

US CLIVAR Summit 2009 Coordination with other Working Groups US CLIVAR AMOC Science Team would like… Input on separation of forced and natural components for AMOC Metrics for evaluating the AMOC in model simulations CLIVAR Working Group on Ocean Model Development DPWG invited to participate in next WG meeting in October 2010, along with AMOC Team NCAR Climate Change & Climate Variability WGs Running additional experiments at request of DPWG

US CLIVAR Summit 2009 Coordination with other Working Groups (continued) NCAR Climate Change and Climate Variability Working Groups Twin perfect model experiments that can be used as a testbed for the DPWG metrics study Time series of CO2 concentrations (ppm) for scenarios B1, A1B, and A2, twentieth- century stabilization from 2000 to 2100, twenty-first century stabilization from 2100 to 2300 for B1 and A1B; (b) time series of globally averaged surface air temperature anomalies (°C), 2000–2300, for the various experiments (from Meehl et al. 2006, JC). * CCSM3 * 40 member ensembles * 60-year integrations Twin #1 : A1B Scenario (runs done) Twin #2 : Year 2000 Stabilization

US CLIVAR Summit 2009 Coordination with the NCAR Climate Change and Climate Variability Working Groups Advantage of these simulations:  Perfect model experiment (allows for a focus on the response to external forcing rather than on potential drift or model spinup)  Runs are long enough to identify response to external forcing (60- year integrations)  There are enough ensemble members to estimate S/N and ensemble spread  Twin experiment strategy allows for studies of how external forcing may be interacting with (and/or projecting on) natural variability

US CLIVAR Summit 2009 Involvement in Workshops The Eighth Workshop on Decadal Climate Variability Decadal Climate Predictability and Prediction: Where Are We? October, 2009; St. Michaels, Maryland Lisa GoddardArun Kumar Jerry Meehl Organizing committee: Lisa Goddard (IRI), Arun Kumar (NOAA-CPC), Mojib Latif (IFM- GEOMAR), Tong Lee (NASA-JPL), Jerry Meehl (NCAR), Vikram Mehta (CRCES), Tony Rosati (GFDL), Jeff Knight (Hadley Centre), and Detlef Stammer (Univ. of Hamburg) The Eighth Workshop on Decadal Climate Variability Decadal Climate Predictability and Prediction: Where Are We? October, 2009; St. Michaels, Maryland Lisa GoddardArun Kumar Jerry Meehl Organizing committee: Lisa Goddard (IRI), Arun Kumar (NOAA-CPC), Mojib Latif (IFM- GEOMAR), Tong Lee (NASA-JPL), Jerry Meehl (NCAR), Vikram Mehta (CRCES), Tony Rosati (GFDL), Jeff Knight (Hadley Centre), and Detlef Stammer (Univ. of Hamburg) Predicting the climate of the coming decades January 11-15, 2010; RSMAS, Miami, FL Workshop goal: The goal of this workshop is to bring together people from different communities who have shared interests in predicting the climate of the coming decades. Key elements: Socioeconomic considerations, Mechanisms of decadal variability, Decadal predictions & forced climate change, Applications, Long-term risk management, Marine ecosystems, Water resources, Public lands, Coastal Management, Airports, Metropolitan planning organizations

US CLIVAR Summit 2009 White Paper in Preparation Focus: Summarize and critique methodologies to distinguish natural decadal variations from anthropogenically-forced variations in order to assess the potential contribution of initialization for decadal predictions. Questions addressed:  Can we estimate the relative amplitude, and spatial structure, of natural and forced decadal variability? What approaches can be used to separate natural decadal variability from anthropogenically forced decadal variations? How does the analysis depend on the chosen method?  How does forced variability interact with the natural variability?  What robust estimates of observed trends and/or decadal variations exist to validate the models? …To be submitted to BAMS September 2009 Focus: Summarize and critique methodologies to distinguish natural decadal variations from anthropogenically-forced variations in order to assess the potential contribution of initialization for decadal predictions. Questions addressed:  Can we estimate the relative amplitude, and spatial structure, of natural and forced decadal variability? What approaches can be used to separate natural decadal variability from anthropogenically forced decadal variations? How does the analysis depend on the chosen method?  How does forced variability interact with the natural variability?  What robust estimates of observed trends and/or decadal variations exist to validate the models? …To be submitted to BAMS September 2009

US CLIVAR Summit 2009 Assembling Databases for Metrics Study 1)CMIP3 Database 2)Twin perfect model experiments with CCSM 40- member ensembles 3)Smith et al data (initialized HadCM3 expt.s) 4)Ben Kirtman’s CCSM simulations 5)Anticipating CMIP5 Decadal Prediction Expt.s 6)What else?

US CLIVAR Summit 2009 Planning for Broad Community Participation in Analysis of Decadal Prediction Experiments CMEP (2004): Coupled Model Evaluation Project 19 Funded Proposals (+ 2 lab funded) 18 Papers published (at least) DRICOMP (2007): DRought In COupled Models Project 16 Funded Proposals Papers to Journal of Climate special issue on drought (together with results from US CLIVAR Drought WG) DECPREP (2010): DECadal PREdictability Project CMEP (2004): Coupled Model Evaluation Project 19 Funded Proposals (+ 2 lab funded) 18 Papers published (at least) DRICOMP (2007): DRought In COupled Models Project 16 Funded Proposals Papers to Journal of Climate special issue on drought (together with results from US CLIVAR Drought WG) DECPREP (2010): DECadal PREdictability Project