7 February 2002

To: Members of the CCSM Climate Change and Assessment Working Group

From: Warren M. Washington

Subject: Update of Model Simulations and Future Plans

I would like to update you about the some of the activities of this working group with regard to climate change simulations and to provide plans for future simulations.

As you may recall, the mostly NSF supported CCSM and the DOE supported efforts including the Parallel Climate Model are merging into a single modeling structure. The DOE Climate Change Prediction Program will work closely within the CCSM program in building improved climate model components and performing climate change simulations that can be used in the IPCC, National Assessment, and other assessment activities. It should be noted that for the DOE supported effort, there is a need to use coupled climate modeling systems that can provide improved estimates of energy related impacts on climate change, especially, with improved regional detail. One of the collaborative efforts involving DOE, NSF, and NASA is Scientific Discovery through Advanced Computing (SciDAC), which is a collaborative effort involving NSF, DOE and NASA aimed at providing U.S. researchers with state-of-the art coupled climate simulation capability. The DOE national laboratories involved are ANL, LANL, LLNL, LBL, ORNL and PNL. The National Center for Atmospheric Research and the NASA/Goddard Data Assimilation Office are the primary, non-DOE collaborators. Bob Malone (rcm@lanl.gov) and John Drake (drakejb@ornl.gov) are co-PIs for the SciDAC project and the primary contacts. The project goals are stated as follows: "The DOE/SciDAC/ACPI is focused on enhancing the nation's climate simulation capability. One strategy is to combine the capabilities of a major climate modeling institution, such as NCAR or GFDL, with those of DOE multidisciplinary laboratories to speed the development of new generations of coupled climate models and component models. These new models must be physically comprehensive, utilize the most advanced algorithms and software engineering practices, and be portable with high performance across the latest computing platforms including highly parallel terascale computers."

More details on the project can be found at http://www.csm.ornl.gov/scidac/CCSM/.

The list of climate forcing for climate change simulation is as follows:

1. Greenhouse gases (GHGs) (CO2, methane, nitrous oxide, CFCs and Stratospheric ozone)

2. Sulfate aerosols (SA)

3. Biomass burning (carbon soot aerosols)

4. Solar changes (SC)

5. Volcanic aerosol (VA)

6. Land Surface Change (LSC)

Summary of CSM (Version 1) Control and Climate Change Simulations

1.  Controls (Present Climate {300 years} and 1870 {300 years})

2.  1% CO2 increase per year from present conditions

3.  Historical 1870 to present (GHGs)

4.  Historical 1870 to present (GHS + SA)

5.  Ensemble (3) Historical 1870 to present (GHGs + SA+ SC)

6.  21st Century Business-as-Usual (BAU)

7.  21st Century IPCC A1 scenario ensemble (3)

8.  21st Century IPCC A2 scenario

9.  21st Century IPCC B2

10. 21st Century IPCC with improved ocean features

More details on the CSM1 climate change simulations can be found at http://www.cesm.ucar.edu.

A complete documentation of the CSM1 can be found in a special issue of the Journal of Climate, Climate Systems Model Special Issue, Volume 11, No. 6, June 1998.

Summary of PCM (Version 1) Control and Climate Change Simulations

1. Controls (Present Climate {300 years} and 1870 {at 860 years and expected extended to 1200 years by May 2002})

2. Ensemble (5) 1% CO2 increase per year from present conditions capped at 2XCO2

3. 1% CO2 increase per year capped at 4XCO2

4. 0.5% CO2 increase per year capped at 2XCO2

5. Ensemble (10) Historical 1870 to present (GHGs + SA)

6. 21st Century Business-as-Usual (BAU) to 2100 ensemble (5); to 2200 (1)

7. 21st Century IPCC A1 scenario to 2100 ensemble (5); to 2200 (1)

8.  21st Century IPCC A2 scenario to 2100

9.  21st Century IPCC B2 scenario to 2100

10. Ensemble (4) Historical 1870 to present (GHGs +SA+ SC)

11. Ensemble (4) Historical 1870 to present (GHGs +SA+ SC + VA)

More information on the PCM stimulations can be found at: http://www.cgd.ucar.edu/pcm/ and at the DOE Program for Climate Model Diagnosis and Interpolation (PCMDI) web site: http://www.pcmdi.llnl.gov/modeldata/PCM_Data/pcgdahome.html.

Documentation of the PCM can be found in Washington et al. Parallel Climate Model (PCM) Control and Transient Simulations, 2000: Climate Dynamics, 16:755-774. An electronic version can be found at http://link.springer.de/ with search names W. Washington and J. Weatherly.

The PCM-CSM-Transitional Model (PCTM) will have limited use. A very small set of simulations will be conducted with the purpose of estimating the climate change sensitivity of a model configuration that has the same atmospheric component and updated ocean, sea ice, and land hydrology.

As an example of a climate change recent result, we show in the following plot of the globally averaged surface temperature anomaly from one member of an ensemble of PCM simulations in which climate forcings of solar, greenhouse gases, sulfate aerosols are included. The gray shaded line is the range of various observed estimates. The new feature is the volcanic forcing introduced in the CSM1 and PCM by Casper Ammann.

Climate Forcing Diagnostics

It is expected that there will be a larger number of diagnostic studies of the causes for the climate change response in the model. This requires making the uncertainties more quantitative. In order to understand the various interactions, special diagnostics will have to be put into the component models that will allow for estimates of the climate change sensitivity to various factors in the overall system.

Ongoing Simulations with CCSM Version 2

The control simulation for the present climate conditions is being conducted at NERSC and has run for approximately 400 years. A 1% CO2 increase per year simulation is started and will be completed sometime in early 2002. The purpose of this simulation is to assess the CCSM2 sensitvity to a doubled amount of CO2. This allows comparison with earlier CSM1 and PCM1 simulations and the results of other modeling groups involved in the IPCC and CLIVAR coupled model intercomparisons.

Suggested Future Simulations are as follows:

Atmospheric horizontal resolution T42

1. 1870 Control Simulations

2. Historical simulation from 1870 to present with greenhouse gases, solar, volcanic, ozone, and sulfate aerosol

3. Several BAU and stabilization scenario simulations such as A2 forcing that start with the historical and end at 2100

4. 20th and 21st century simulations with estimated changes in greenhouse gases, solar, ozone, and aerosol distributions (e.g. A2 and BAU from IPCC and Wigley)

Atmospheric horizontal resolution T85

Because of the large increase in computer time required for T85 simulations, we expect to perform a few 20th and 21st century experiments with the forcing listed in item 4 above.