NCAR releases version 4 of CCSM

2 April 2010  •  A completely upgraded and more advanced version of the Community Climate System Model (CCSM) became available to university and laboratory researchers with the release of CCSM4.0 on 1 April. Supported primarily by NSF and the U.S. Department of Energy, CCSM4 is a state-of-the-science tool that allows scientists to explore the history of Earth’s climate, investigate processes and mechanisms responsible for current climate variations and change, and estimate future states of the climate system to guide adaption strategies and policy formulation.

Model depictions of ENSOThis graphic shows the improvement in the CCSM's depiction of the El Niño/Southern Oscillation within multicentury control simulations. When compared to the last 60 years of sea-surface temperatures for the Niño 3.4 region (top), CCSM4.0 (middle) captures the general behavior of ENSO, including its frequency and amplitude, more closely than does CCSM3.0 (bottom). (Graphic courtesy Adam Phillips, NCAR/CCSM.)

Each of the major components of CCSM—modules for ocean, land, sea ice, and atmosphere, as well as the modeling infrastructure—has been significantly improved with many added capabilities, says NCAR’s James Hurrell, chair of the CCSM Scientific Steering Committee. 

The CCSM4 website includes an overview of the many notable improvements. For instance, the model now includes

  • an improved portrayal of deep convection (showers and thunderstorms),           
  • the ability to depict transient changes in land cover,
  • a new scheme for tracking melt ponds atop sea ice,
  • and a new scheme for parameterizing ocean overflows, which are density-based currents that hug the ocean bottom and flow over the continental slope.

CCSM4 also now includes a single foundation of code to support tasks that may use only a single processor (such as developing a new parameterization) or tens of thousands of processors (such as running very high resolution simulations). “We’ve taken a completely new approach with respect to the high-level design of the system,” says Mariana Vertenstein, head of the CCSM’s software engineering group at NCAR.

CCSM4 is already being used to contribute to an ambitious set of climate experiments that will be featured in the fifth assessment report (AR5) of the Intergovernmental Panel on Climate Change, which is set for release in 2013. All CCSM4 simulations in support of the AR5 are scheduled for public release by the end of 2010.

Next in the pipeline: CESM

Early this summer, NCAR will unveil the successor to the CCSM: the first version of the Community Earth System Model (CESM1.0). In addition to the new physical climate system component models included in the CCSM4.0 release, CESM1.0 will enable the carbon cycle in the land, ocean, and atmosphere to be fully predicted, rather than being partially specified as in previous versions of the model. In addition to an interactive carbon cycle, CESM1.0 will also feature an updated atmospheric chemistry component, an updated version of the Whole Atmosphere Community Climate Model (WACCM), and a new land ice component to study the role of the Greenland and Antarctic ice sheets in climate. 

Simulations with CESM1.0 are also being conducted for inclusion in NCAR’s modeling contribution to IPCC AR5. More details on CESM will appear in the spring issue of UCAR Magazine.