The IPCC Data Distribution Centre GCM Experiments

A large number of climate change experiments using Global Climate Models (GCMs) have been completed in recent years, both equilibrium and transient experiments, and both experiments forced with changes in greenhouse gas concentrations alone and those forced with greenhouse gas and sulphate aerosol changes. A number of parallel experiments have also been completed using high resolution Regional Climate Models. Results from a considerable number of these experiments have been used in climate change impacts and adaptation assessments. It is not always easy, however, to know which experiment has been used in an impacts study, nor how the particular modelling results fit into the larger population of GCM climate change experiments.

The IPCC Task Group on Scenarios for Climate Impacts Assessments defined a set of criteria that have been applied to identify GCM experiments whose results could be deposited at the IPCC DDC, experiments which could therefore form the basis for impacts assessments undertaken from 1998 onwards. These criteria included:

• An IS92a-type forcing scenario
• Historically-forced integrations
• Integrations without/with aerosol forcing and up to 2100 for greenhouse gas only
• Integrations with results available now and with data lodged in the public domain
• Documented models
• Models that have participated in AMIP/CMIP

These criteria led to an initial selection of experiments from five modelling centres, with the possibility of others to be added in subsequent months as they qualify for inclusion. An inventory of recent and current GCM experiments (GCM Inventory) has been compiled by the TGCIA. The five modelling centres currently selected for inclusion in the DDC are:

HadCM2

ECHAM4

GFDL-R15

CGCM1

CSIRO-Mk2

• The UK Hadley Centre for Climate Prediction and Research (HadCM2)
• The German Climate Research Centre (ECHAM4)
• The Canadian Centre for Climate Modelling and Analysis (CGCM1)
• The US Geophysical Fluid Dynamics Laboratory (GFDL-R15)
• The Australian Commonwealth Scientific and Industrial Research Organisation (CSIRO-Mk2)

Monthly time-step results from these modelling centres have been lodged with the IPCC DDC. The full sets of monthly results from these experiments (and more detailed technical information) can be obtained from the DDC GCM Archive, although daily fields are only available directly from the respective modelling centre. We provide here a brief overview of the various experiments and a summary of their simulated global-mean time-series and changes with those published by the IPCC in 1996 in the Second Assessment Report. By visiting the Data Visualisation pages, it is possible to plot 30-year mean changes fields from these experiments, comparing them with each other and with the 1961-1990 observed climatology. These aggregate 30-year mean GCM fields can be downloaded from the Data Download Pages.