Paleo Documentation

CCSM3.0 Paleo Users Guide

The Community Climate System Model, version 3 (CCSM3) is a legacy version of the Community Earth System Model (CESM).  Support for CCSM3 and all previous versions of CCSM has expired.  The tools described in this documentation were developed at the National Center for Atmospheric Research (NCAR) but are no longer actively maintained

For more information on currently supported versions of the model see the CESM documentation:  http://www2.cesm.ucar.edu/models.

Modeling paleoclimate with CCSM3

Using the CCSM3/CESM1 model for paleoclimate modeling requires complex, multi-step modifications to the input and forcing files used by the model, particularly for Deep Time simulations where continental configurations have changed.  Researchers may need to modify these procedures to accommodate newer versions of the CESM1 model, or for the computer resources available on their home machines.   To gain more understanding about the CESM1 component models and input files, see the CESM1 documentation http://www2.cesm.ucar.edu/.

This document describes the procedures for creating a CCSM3 fully coupled fully coupled (all components active) paleoclimate simulation.  We do not describe the creation of the forcing files used in Data Model components or in stand-alone component model runs.

We provide tools and examples of the process used to create paleoclimate simulations using the computing resources at NCAR.  This document is to be used as a guide; researchers may need to modify the processes to accommodate their research interests, or adapt the tools to their available computer resources.

Throughout this User’s Guide we differentiate between the procedures required to create (1) near-modern (e.g., Quaternary, Pliocene) or (2) Deep-Time (pre-Quaternary) model simulations.  In near-modern simulations, the continents are in their present-day positions, and the land/sea masks do not require significant modification. Quaternary modelers are often able to use existing forcing files to simulate past climate.  By contrast, deep-time simulations require drastic modifications to the land/sea mask, and the modeler is responsible for providing the orographic/bathymetric maps for their geologic period of interest.