CCSM is a collaborative effort between NCAR and non- NCAR scientists to build a comprehensive climate system model. The project is supported by the National Science Foundation (NSF) and the Department of Energy (DOE) and NCAR is also establishing links to the NOAA GFDL. CCSM includes an advisory board, a scientific steering committee and nine different working groups focusing on atmosphere, ocean, sea ice, land surface, biogeochemistry, climate change, natural variability, paleo-climate, and software engineering.

Climate change experiments conducted at NCAR involve aspects such as for instance greenhouse gases, direct and indirect sulfate aerosols, stratospheric ozone, biomass burning and carbon aerosols, land and vegetation changes, volcanic eruptions, and various energy and emissions use strategies, as the speaker indicated. It is also studied how accurate the atmosphere model responds to El Niño. Researchers consider shifts in precipitation due to warm and cold tropical sea surface temperature anomalies and examine the change in the observed precipitation from the global precipitation climatology project.

Mr. Washington described some example activities within the CCSM initiative such as CAM2 focusing on improved longwave radiation and clouds, prognostic cloud water formulation, changes to convective precipitation, and increased vertical resolution; and the ocean model POP1.4 with displaced North Pole into Greenland, anisotropic horizontal viscosity formulation, increased horizontal resolution, and revised formulation of the G-M eddy scheme.

The speaker also mentioned CSIM which simulates new elastic-viscous-plastic (EVP) ice rheology by generating a new thermodynamic model, including a multi-category ice thickness scheme; and CLM that involves a new biogeophysics formulation for multilayer soil water and ground T(z) formulation, a multilayer snow model with compaction and a river runoff scheme.

The control simulation expands out to year 1000 years. There is no flux correction applied. The model drifts -0.04 K/century in surface temperature and -0.07 K/century in volume average ocean temperature. Mr. Washington noted that CCSM2 tries to address more serious biases like tropical biases, the high latitude warm bias and the tropical tropopause. In September 2003, CCSM2 will be ready for IPCC FAR simulations.

The experiments still continue and are discussed at bi-weekly meetings. The researchers have drafted a list of experiments with coupled and uncoupled models. They found out that the coastal upwelling regions are critical to deep tropics and that uncoupled models produce correct tropical seasonal cycle, but when they are coupled they drift.

In preparation for the IPCC simulations, the scientists apply changes to all model components, especially to the atmosphere. They have implemented a sulfate cycle and aerosol-radiations links as well as other aerosol data and an improved boundary layer scheme. For the atmospheric model, finite volume and spectral dynamical cores are used. Updates are made to the shortwave scheme, the H2O continuum and to the cloud parameterisation next to the introduction of prognostic aerosols. The prognostic cloud water scheme has been updated.

In the ocean model, minor changes have been made to the horizontal viscosity scheme and to the formulation and numerical implementation of KPP. There is still work underway with the goal to create deeper boundary layers. Mr. Washington told the audience that the solar absorption scheme will be changed to one that is based upon observations.

in the land model, dust emission and deposition have been added as well as volatile organic compound (VOC) emissions. The canopy turbulence modelling has been improved and snow fraction integrated. Furthermore, there is interception/ run-off and the new Wang's leaf temperature calculation is used. Simulation of dry deposition of gases on vegetation has equally been provided for.

As for the most challenging problems within CCSM2, Mr. Washington named aspects such as double ITCZ, an excessive cold pacific cold tongue, an excessive warm eastern boundary water, a cold tropical tropopause, and excessive high latitude surface temperatures. In addition, the speaker gave an overview of CCSM2 results with an emphasis on their variability.

Current tasks within CCSM2 to fulfil include the use of a higher resolution atmospheric model, improving the treatment of clouds, and developing a fully interactive carbon cycle.

According to Mr. Washington, the general theme for the next five years of the CCSM Climate and Assessment Working Group is twofold: first quantifying uncertainty in climate change projections and second integrate all the steps to accomplish this objective. There is no "forcing repository needs so groups can use the seme forcing(s) and single forcing experiments are still useful.

Plans are made to improve regional climate simulation and extremes with higher resolution, an atmospheric component, T85, T170 coupled simulations. There is a need for more outputs from the model in time and space for extremes analyses. Researchers also aim to create probabilistic projections of climate change using

Ensemble simulations with various forcings and scenarios. Finally, they want to understand the model response to changes of forcing. The climate sensitivity is likely to be the main issue for the next IPCC.

Single model sensitivity experiments will be conducted with CCSM for the atmosphere only or otherwise for mixed layer slab coupled experiments. There will also be co-ordinated experiments involving other models from different modelling centres in addition to CCSM with an analysis of 1000 year runs from PCM and CCSM. Mr. Washington stated that the key issue for this objective forms computer time in 2003-2005, as well as model data transfer, and storage and access.

An extensive project constitutes the DOE Earth System Grid/SciDac Development with simulations at NCAR, LANL, NERSC, and ORNL of up to 70 Tbytes of data so far and with the archives at PCMDI, NERSC, NCAR, ORNL, and LANL. There will be easy access for transferring large data sets and a catalogue system across the distributed system. This is a co-operative programme between the DOE laboratories and NCAR to be found at the Earth System Grid Web site.

Mr. Washington concluded by citing the most common scientific questions that circulate for IPCC:

• What about mitigation versus adaptation?
• What are sign and nature of feedbacks in the climate system?
• What are the factors that affect climate sensitivity?
• What are the effects of resolution?
• Will ENSO change?
• Will Asian-Australian monsoon change?
• Will mid-latitude storm tracks change?
• Will the ocean thermohaline circulations change?
• How will a different stabilisation of emissions effect the climate?