2/27/06CAB Meeting Scientific and Technical Plans for IPCC AR5 Bill Collins With input from Lawrence Buja and Jerry Meehl National Center for Atmospheric Research Boulder, Colorado

2/27/06CAB Meeting Our principal scientific targets (CAB Meeting, June 2005) Major objective: Develop, characterize, and understand the most realistic and comprehensive model of the observed climate system possible. Subsidiary objectives: –Analyze and reduce the principal biases in our physical climate simulations using state-of-the-art theory and observations. –Simulate the observed climate record with as much fidelity as possible. –Simulate the interaction of chemistry, biogeochemistry, and climate with a focus on climate forcing and feedbacks.

2/27/06CAB Meeting Interaction of the CCSM community with the IPCC process We design the model we want for Earth system science -- this model will naturally be ideal for IPCC. Our collective objective should be novel experiments with CCSM4 -- these add tremendous value above and beyond the IPCC scenarios.

2/27/06CAB Meeting Possible components of CCSM4 (CCSM Plenary, June 2005) Atmosphere Ocean Coupler Sea IceLand C/N Cycle Dyn. Veg. Ecosystem & BGC Gas chem. Prognostic Aerosols Upper Atm.

2/27/06CAB Meeting Configuration of CCSM4: Open issues The physical components: –What improvements will be ready to address long-standing biases? –What major modifications will be included in CAM? –What resolutions will we use? What can we afford? The chemical and biogeochemical components: –What terrestrial ecosystem model will we use? –What mechanism for gaseous chemistry will we use? –What representation of aerosols will be adopted? –What lid will we adopt for the upper atmosphere? –Will dynamic vegetation be compatible with the simulated climate? Computational cost: –What changes can we make to the numerical formulation to increase scaling by 10x? By 25x?

2/27/06CAB Meeting The timeline for IPCC AR5 (CAB Meeting, June 2005) Assumptions: It is likely that the AR5 report will be issued 6 years after AR4, in Following the precedent in AR4, the simulations will have to be finished two to three years ahead, in mid-2011 at the latest. Therefore we need to have CCSM4 ready in 2009 (at the latest). This means we have just four years to accomplish our objectives AR5 ProcessCCSM4 DevelopmentCCSM4 Release

2/27/06CAB Meeting A more detailed timeline for IPCC runs Lawrence Buja

2/27/06CAB Meeting Lessons Learned from IPCC AR4 (CAB Meeting, January 2005) 1.Start with an experimental plan 2.Develop forcings early in the process of experimental design and model development 3.Design and test methods for equilibration of CCSM with present-day and pre-industrial conditions. 4.Plan and test data processing to insure timely data transfer to IPCC archive(s). 5.Develop scientific requirements for: a.Model capabilities: e.g., chemical processes, etc. b.Spatial resolution of the CCSM component models c.The size of the ensembles for 20 th C. and scenario runs

2/27/06CAB Meeting Goals of the design exercise Identify major scientific objectives of our IPCC runs –What do we want to explore using 20c3m simulations? –What hypotheses are we testing with scenario runs? –What can we learn about our climate model and the climate from the multi-model ensemble? Identify subsidiary scientific objectives: for example –Tests of new methods for understanding climate sensitivity and climate feedbacks. –Development of state-of-art emissions data sets and simulations of forcing agents (e.g., BC and OC aerosols) Map/integrate these objectives into the CCSM science plan Design the simulations: –Spin-up process –Ensemble size Create an implementation plan

2/27/06CAB Meeting Proposal for draft outline of IPCC plan 1.Introduction: the interaction of CCSM and IPCC A.What have we learned from the 20c3m runs? B.What have we learned from multi-model papers? C.What’s new in the IPCC AR5? 2.Scientific objectives for the IPCC AR5 A.Major objectives: e.g., quantifying carbon-cycle feedbacks B.Minor objectives: e.g. quantifying aerosol indirect effects 3.Description of the forcing agents: A.Well-mixed GHGs and the C/N cycle B.Tropospheric and stratospheric ozone C.Aerosols: direct, semi-direct, and indirect effects D.Solar variation E.Land-use change: effects of agriculture, fires, urbanization

2/27/06CAB Meeting Proposed outline (cont.) 4.Description of the experiments: A.Requirements for ensemble size B.Experiments to determine model resolution C.Description of 20c3m and scenario integrations D.Subsidiary experiments, e.g., pre-industrial controls, etc. 5.Description of the model spin-up procedure: A.Initial conditions for prognostic fields B.Acceleration techniques (if any) C.Evolution or boundary conditions for forcing agents 6.Implications for the CCSM program: A.Coordination on model configuration and capabilities B.Coordination on forcing agents C.Coordination on configuration of experimental configuration.

2/27/06CAB Meeting Proposed outline (cont.) 7.Resource requirements: A.Computer time: 1)Estimation of CPU hours / year of simulation 2)Estimation of total CPU time required for IPCC runs and model development leading to IPCC version of CCSM4. 3)Plan for acquisition of computer time. B.Human resources: 1)Identification of the major software engineering projects. 2)Estimation of the person-years of SE effort required. C.Post-processing, archival, and data transfer 1)Estimate of model data per simulation year 2)Total data volume for the IPCC simulations 3)Identification of archival sites 4)Estimation of processing and transfer throughput 8.Timelines and a decision tree 9.Distribution and analysis of IPCC simulations

2/27/06CAB Meeting Planning by WGCM and other groups Workshop in summer 2006 for modeling groups and scenario developers for IPCC AR5: –Participants include: WGCM AIMES SPARC Other IGBP groups –Product of meeting: recommendations for AR5 scenarios Meeting of WGCM and AIMES in September 2006: –Product: white paper outlining plans for ESMs & scenarios –CCSM should present its plans and configuration for AR5 at this meeting.

2/27/06CAB Meeting Provisional list of AR5 required simulations Standard runs from all groups: –Equilibrium mixed-layer 2xCO 2 runs –1%/year 2xCO 2 run for TCR from AOGCMs –All-forcings integrations for 20th century –All-forcings integration for 21st century with 1 scenario (A1B?) New adaptation/mitigation scenario integrations for ESMs

2/27/06CAB Meeting Conclusions Provisional timeline for CCSM4 and IPCC AR5: –Freeze of model formulation in late 2008 –Public release in summer 2009 –Initiation of historical simulations in spring 2010 –Completion of scenario integrations in spring 2011 This schedule gives three years for model development. We should consider a coordinated process to resolve open issues for the configuration of CCSM4. This process should stem from our experimental objectives for studies of coupled Earth system.

2/27/06CAB Meeting Some big chemistry questions What do we want chemistry for? –Short-lived forcing agents: Aerosols Ozone How much of the chemistry must be interactive? What’s the lid on the model? –Stratopause –Mesopause –Higher? Where do we get the historical emissions data sets for chemical species? What are your metrics for fidelity?