20th Century Climate in Coupled Models: a CMIP pilot project

From: Jerry Meehl (meehl@meeker.ucar.edu)

To: CDKKL@NASAGISS.GISS.NASA.GOV, abeouchi@ccsr.u-tokyo.ac.jp, ach@dar.csiro.au, asgeir.sorteberg@gfi.uib.no, barthele@cerfacs.fr, cmglr@giss.nasa.gov, cubasch@dkrz.de, dinar@inm.ras.ru, esch@dkrz.de, fairhead@lmd.jussieu.fr, george.boer@ec.gc.ca, greg.flato@ec.gc.ca, hbg@dar.csiro.au, hellbach@dkrz.de, hogan@nrlmry.navy.mil, jbahn@pusan.ac.kr, jonathan.gregory@metoffice.com, jtkon@ncar.ucar.edu, kimoto@ccsr.u-tokyo.ac.jp, letreut@lmd.jussieu.fr, meagles@meto.gov.uk, meehl@ncar.ucar.edu, noda@mri-jma.go.jp, r.colman@bom.gov.au, rjs@gfdl.gov, roeckner@dkrz.de, sbp@bom.gov.au, schneide@cola.iges.org, tcjohns@meto.gov.uk, terray@cerfacs.fr, yyq@lasg.iap.ac.cn, zxh@lasg.iap.ac.cn

Subject: New CMIP Pilot Project

Cc: B.McAvaney@bom.gov.au, covey1@llnl.gov, gates5@llnl.gov, john.f.mitchell@metoffice.com, latif@dkrz.de

November 8, 2002

Dear CMIP modeling group representative,

At the recent meeting of the Working Group on Coupled Models (WGCM), the parent committee of CMIP, it was decided to go forward with a new CMIP pilot project called "20th Century Climate in Coupled Models" (20C3M).

WGCM recognized that many modeling groups are making 20th century climate simulations with various combinations of forcings and different forcing datasets. Previously CMIP has involved idealized forcing experiments (1% CO2 increase) that facilitate direct comparison. The 20th century simulations will all be somewhat different, but it was recognized that useful and enlightening intercomparisons could still be performed for certain applications with these runs.

Since the choices of forcing datasets and combinations of forcings are still considered to be active research problems, it was decided that WGCM and CMIP would not dictate new runs be done with selected forcings, but that runs done by the groups as part of their ongoing research programs would be collected. These runs would represent the various groups' best effort to simulate 20th century climate, with the stipulation that there must be documentation of the forcings and forcing datasets used in the simulations.

Possible applications for the model data collected for the 20C3M pilot project would include (but are not limited to) climate change detection through multi-model and multi-non-standardized forcing analyses. Such studies are expected to be of interest in global and regional scale climate change detection and attribution for multiple variables, and in deriving uncertainty measures for future climate change based on the ability of the models to reproduce 20th century climate. Additionally, model validation, decadal variability studies and model assessment work would complement analyses of the control runs already collected in CMIP.

Requirements for Contributions

Data: Since this is a pilot project, we are requesting only a limited subset of the model output (as opposed to CMIP2+ where all model output was collected). The requested model data for a time period of model simulation starting typically in the late 19th century and ending in 2000:

* both soil moisture fields in kg/m2
** 1000, 925, 850, 700, 600, 500, 400, 300, 250, 200, 150, 100, 70, 50, 30, 20, 10 hPa

Ideally, the full set of variables can be collected from participating members, but subsets (that should include monthly surface air temperature) are also acceptable.

Ensembles: 3 members recommended, but fewer or single simulations are also welcome.

Time frame: If possible, from late 19th century to 2000, but if this is not possible, the period 1961-2000, to allow comparison with observations using the same climatology and to go as far into the emerging anthropogenic signal as possible.

Format: NetCDF Climate and Forecast (CF) Metadata Conventions (see http://www.cgd.ucar.edu/cms/eaton/cf-metadata).

Comparable CMIP runs: Contributing coupled GCMs should submit or have submitted control runs to CMIP, and have made a 2xCO2 equilibrium run with a slab ocean configuration.


  1. List of anthropogenic forcings (e.g. CO2, GHG, sulfate aerosol) and/or natural forcings (e.g. solar, volcano)

  2. Source and possible reference for forcing agent datasets

  3. If possible, estimates of radiative forcing for individual forcing agents and net forcing (e.g. experiment minus control), global values annually, or decadally, or with spatial pattern information

  4. Initialization and spin-up procedure

  5. Land-sea mask

  6. Orography and bathymetry

  7. Land surface characteristics (documentation of soil, vegetation - climatological or interactive)

  8. Surface albedo characteristics and functional dependence (e.g. documentation of snow ageing and masking, ice ponding)

Hopefully this data request can be fulfilled during the next month or two. When we have a sufficient representation of 20th century data in the archive at PCMDI, we will send out a new subproject announcement soliciting analyses of the database as we have done for the other phases of CMIP. Our target for sending out this announcement is early February, 2002. If you anticipate delays in fulfilling this request, please let me know as soon as possible.

If you have any questions or problems, please contact Curt Covey at PCMDI (covey1@llnl.gov). He will be handling the archival of the model data. Please contact him when you are ready to start transferring your model data.

On behalf of the CMIP Panel (Jerry Meehl, chair; Curt Covey, Mojib Latif, Bryant McAvaney, and Ron Stouffer), and Gabi Hegerl who has helped put the 20C3M announcement together, I thank you for your support of CMIP so far, and look forward to your participation in 20C3M!

Best regards,

Jerry Meehl (for the CMIP Panel)