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Data

Canadian Centre for Climate Modelling and Analysis


GHG+A IPCC IS92a Scenario Runs

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Data available through our interactive web server
Atmosphere:

Ocean:
Datasets available by FTP only
ETA level data

This ensemble of 3 simulations was performed with the second version of the CCCma Coupled Global Climate Model CGCM2. This model is based on the earlier CGCM1 (Flato et al. (2000), but with some improvements to address shortcomings identified in the first version. In particular, the ocean mixing parameterization has been changed from horizontal/vertical diffusion scheme to the isopycnal/eddy stirring parameterization of Gent and McWilliams (1990), and sea-ice dynamics has been included following Flato and Hibler (1992). The model is forced by an effective greenhouse forcing corresponding to that observed from 1900 to 1996 and an increase of CO2 at a rate of 1% per year thereafter until year 2100 (the IPCC "IS92" scenario). The direct effect of sulphate aerosols is also included by increasing the surface albedo as in Reader and Boer (1998). A description of CGCM2 and a comparison, relative to CGCM1, of its response to increasing greenhouse-gas forcing can be found in Flato and Boer (2001).

All three runs are performed with the same greenhouse gas and aerosol forcing. The only difference is that the runs are initiated from different initial conditions. The reason for doing an ensemble of integrations is to reduce the natural climate variability by taking the ensemble average over all three runs. The differences between the individual integrations are entirely due to natural variability and not due to the differences in the model or forcing.

A total of 201 years of monthly data is available (see Notes for errata/updates). The first record is for year 1900 month 1 and the last one is for year 2100 month 12. Annual, seasonal and monthly climatologies are also available for four 21-year time windows: 1900-1920, 1975-1995, 2040-2060 (approx. CO2 doubling relative to the 1975-1995 level) and 2080-2100 (approx. CO2 tripling).

Twice- and 4-times daily data on model ETA level from the run labeled GHG+A IS92a 3 are available for several time windows 1964-1968 (2x daily), 1969-1994 (4x daily), 2021-2038 (2x daily) and 2039-2059 (4x daily) from the CCCma anonymous ftp server ftp.cccma.ec.gc.ca/pub/data/cgcm2/ghga3/.

The data are provided on a 97x48 Gaussian grid (approximately 3.75° lat x 3.75° long). They have also been linearly interpolated to Northern and Southern Hemisphere polar stereographic grids.

Decadal means of ocean temperature, salinity, velocity components and sea level rise are available, starting from the year 1901 (20 decades). Only the steric (thermal expansion) component of sea level rise integrated from surface to 1175m depth is calculated. Any contribution due to glacier melt is ignored. Sea-level rise is computed as the difference of the vertically integrated specific volume between corresponding decades of the GHG+A and CONTROL experiments (essentially as in Bryan (1996)). The data is provided on a 193x96 grid (approximately 1.88° lat x 1.88° long).

The user should be aware that grid box values are not directly comparable to station data. Climate models attempt to represent the full climate system from first principles on large scales. Physical "parameterizations" are used to approximate the effects of unresolved small scale processes because it is not economically feasible to include detailed representations of these processes in present day models. Caution is therefore needed when comparing climate model output with observations or analyses on spatial scales shorter than several grid lengths (approximately 1000 to 1500 km in mid-latitudes), or when using model output to study the impacts of climate variability and change. The user is further cautioned that estimates of climate variability and change obtained from climate model results are subject to sampling variability. This uncertainty arises from the natural variability that is part of the observed climate system and is generally well simulated by the climate models.

Notes:

  • Mean sea level pressure data from the GHG+A runs are replaced with the corrected versions that are consistent with those from the A2/B2 runs. (August 30, 2001)
  • Decadal ocean temperature and salinity and sea level rise data are added. (July 13, 2001)
  • The snow water equivalent files for the GHG+A runs have been replaced with the corrected versions on June 13, 2001. The quality of the older versions have been downgraded by a packing routine. (June 13, 2001)
  • Mean 2m wind speed data are added. Mean 2m wind speed in this simulation is calculated from daily averaged zonal and meridional wind components. (Oct. 18, 2000)
  • Monthly/annual data and climatologies are added. (Sept. 5, 2000)

References:

Bryan, K., 1996: The steric component of sea level rise associated with enhanced greenhouse warming: a model study. Climate Dynamics , 12, 545-555 (Abstract).

Flato, G.M., and G.J. Boer, 2001: Warming Asymmetry in Climate Change Simulations, Geophysical Research Letters, 28, 195-198 (Available on-line).

Flato, G.M., G.J. Boer, W.G. Lee, N.A. McFarlane, D. Ramsden, M.C. Reader, and A.J. Weaver, 2000: The Canadian Centre for Climate Modelling and Analysis Global Coupled Model and its Climate. Climate Dynamics, 16, 451-467 (Abstract).

Flato, G.M., and Hibler, W.D. III, 1992: Modelling Pack Ice as a Cavitating Fluid. J. Phys. Oceanogr. 22, 626-65 (Abstract).

Gent, P.R., and J.C. McWilliams, 1990: Isopycnal Mixing in Ocean Circulation Models. J. Phys. Oceanogr., 20, 150-155(Abstract).

Reader, C.M., and G.J. Boer, 1998: The modification of greenhouse gas warming by the direct effect of sulphate aerosols. Climate Dynamics, 14, 593-608 (Abstract).