Climate Change Working Group (CCWG) July, 2004 Co-chairs: Gerald A. Meehl, Ben Santer, and Warren Washington

Currently Active Global Coupled Climate Models PCM atmosphere: CCM3.2, T42, 18L ocean: POP, 2/3 to 1/2 degree in eq. Tropics, 32L, biharmonic diffusion, Pacanowski/Philander mixing sea ice: dynamic (EVP), thermodynamic land surface: LSM CCSM2 atmosphere: CAM2, T42, 26L ocean: POP, 1 to 1/2 degree in eq. Tropics, 40L, GM, KPP sea ice: dynamic (EVP), thermodynamic land: CLM CCSM3 atmosphere: CAM3, T85, 26L ocean: POP, 1 to 1/2 degree in eq. Tropics, 40L, GM, KPP sea ice: dynamic (EVP), thermodynamic land: CLM (T42 class models run 8 years per day on IBM SP Power4; T85 is about a factor of two slower)

CCSM3 is current active model for new climate change experiments for the CCWG CCSM2 used mainly for CMIP thermohaline circulation sensitivity experiments PCM being run only for limited experiments to leverage information from the large archive of completed 20 th and 21 st century climate simulations

PCM 20 th, 21 st and 22 nd Century Simulations Volcano-only, , 4 members Ozone-only, , 4 members GHG-only, , 4 members Sulfate aerosol-only, , 4 members GHG+ozone, , 4 members Solar+ozone, , 4 members Solar-only, , 4 members GHG+sulfates+ozone, , 10 members GHG+sulfates+ozone+solar, , 4 members GHG+sulfates+ozone+solar+volcano, , 4 members Solar+volcano, , 4 members Solar+volcano+ozone, , 4 members GHG+sulfates, , 4 members control simulation (1500 years) 1% CO2 increase to doubling (5 members), and quadrupling (1 member); 150 years at 2XCO2, 150 years at 4XCO2; (CMIP) ACACIA “Business as Usual”, 5 members, ; 1 member to 2200 ACACIA “stabilization”, 5 members, , 1 member to 2200 SRES A2,B2, A1FI (single members), A1B and B1 (four members), SRES A1B and B1 stabilized at 2100 values run to 2200 (four members), one each to th century stabilization to 2100 (four members) Land surface change experiments

The PCM set of simulations represents perhaps the largest global coupled model dataset of multi-member ensemble 20 th and 21 st century climate simulations, performed with a single model, currently in existence Over 190 simulations Over 21,000 years of simulation 100 Tb

Another source for model output A large database of PCM and CCSM2 results have been postprocessed and quality controlled for easy distribution to the scientific community. Over 80 PCM runs –Atmospheric monthly and daily data. –Oceanic monthly data. CCSM2.0.1 control run (years ) See for details or

List of runs for IPCC AR4: 1. 20th century simulation to year 2000, then fix all concentrations at year 2000 values and run to 2100 (CO2 ~ 360ppm) 2. 21st century simulation with SRES A1B to 2100, then fix all concentrations at year 2100 values to 2200 (CO2 ~ 720ppm) 3. 21st century simulation with SRES B1 to 2100, then fix all concentrations at year 2100 values to 2200 (CO2 ~ 550ppm) 4. 21st century simulation with SRES A2 to % CO2 run to year 80 where CO2 doubles at year 70 with corresponding control run year (minimum) control run including same time period as in 1 above 7. 2XCO2 equilibrium with atmosphere-slab ocean 8. Extend one A1B and B1 simulation to % CO2 run to quadrupling with an additional 150 years with CO2 fixed at 4XCO % CO2 run to doubling with an additional 150 years with CO2 fixed at 2XCO2

CCSM3 T85 IPCC Simulations

PCM: 2XCO2 = 2.1°C TCR = 1.32 °C CCSM3: 2XCO2 = 2.7 °C TCR = 1.46 °C

Earth Simulator CCSM3 Simulations

Global coupled climate model analyses for the IPCC AR4 Modeling groups around the world have agreed to perform an unprecedented set of coordinated 20 th and 21 st Century climate change experiments, in addition to commitment experiments extending to the 22 nd Century, for the IPCC Fourth Assessment Report. WGCM is coordinating an international effort to collect, archive and analyze output from this multi-model dataset for direct input to the IPCC AR4 in The WGCM Climate Simulation Panel has been set up to oversee this effort [chair, Gerald Meehl (NCAR, USA), John Mitchell (Hadley Centre, U.K.), Bryant McAvaney (BMRC, Australia), Curt Covey (PCMDI, USA), Mojib Latif (MPI, Germany), and Ron Stouffer (GFDL, USA)]. This panel is coordinating the collection and archival of the multi-model output at PCMDI. The initial deadline for submission of model data is September 1, 2004.

Individuals and groups can sign up before September 1, 2004 to analyze aspects of the simulations. An announcement has been made inviting open participation (CLIVAR Exchanges, EOS, BAMS, ). Contact if you are interested in participating. Results will be presented at a Workshop on Analyses of Climate Model Simulations for the IPCC AR4 March 1-4, 2005, convened by U.S. CLIVAR, and hosted by the International Pacific Research Center, University of Hawaii. Scientific papers describing the results presented at the workshop must then be written by the respective investigators, and submitted to peer-reviewed journals by the time of the Second Lead Authors Meeting in May, 2005, in order to be fully included and assessed in the AR4 as specified by the guidelines of IPCC.

a. Scientific objectives of the CCWG Main theme: Quantifying uncertainty in climate change projections Requirements: 1. Improve regional climate simulation and extremes: higher resolution atmospheric component, T85, T170 coupled simulations; more outputs from model in time and space for extremes analyses 2. Probabilistic projections of climate change: Ensemble simulations with various forcings and scenarios 3. Understand model response to changes of forcing; climate sensitivity a main issue

Planned CCSM3 simulations T170 AMIP simulation T170 CCSM3 coupled simulation, T85 Historical simulation from 1870 to 2000 (GHGs + SA +SAI +SV+ V + O) (130 years) with sulfate aerosols (direct and indirect effect) T85 Historical simulation from 1870 to 2000 (GHGs + SA +SV+ V+ O + CA) (130 years) with carbon aerosols varying in space and time T85 Historical simulation from 1870 to 2000 (GHGs + SA +SV+ V+ O + DA) (130 years) with dust aerosols T85 Historical simulation 1870 to 2000 with sulfate indirect only T85 Historical simulation 1870 to 2000 with dust aerosols only T85 Historical simulation 1870 to 2000 with carbon aerosols only