January 7, 1997
In our announcement for the first phase of the Coupled Model Intercomparison Project (CMIP1) one year ago, we indicated that the second phase of CMIP (CMIP2) would involve a comparison of coupled model climate sensitivity. Therefore, on behalf of the World Climate Research Programme (WCRP) Climate Variability (CLIVAR) Numerical Experimentation Group Two (NEG 2), the CMIP Panel (Jerry Meehl, chair; George Boer, Curt Covey, Mojib Latif, Ron Stouffer) is pleased to invite your group to participate in CMIP2. Details are included in this announcement.
In terms of an update as to the status of CMIP so far, we had a very positive response to the CMIP1 announcement. We now have data from 18 global coupled models representing virtually every group internationally with current functioning global coupled GCMs. The national breakdown is as follows: Australia (2), Canada (1), France (2), Japan (2), Germany (3), U.K. (1), and U.S.A. (7). About half use some form of flux adjustment, and intercomparison calculations are underway. For the status of CMIP, you can check out the web site: http://www-pcmdi.llnl.gov
Thus we are now ready to embark on CMIP2. At the September 1996 meeting of CLIVAR NEG2 in Victoria, Canada, it was decided that CMIP2 will be an intercomparison of 1% per year compound CO2 increase integrations (80 years in length) where CO2 doubles at around year 70.
As in CMIP1, we are soliciting contributions from global coupled general circulation models (GCMs) that operate over the complete global domain and include, at minimum, atmosphere, ocean and sea ice components. Any type of spin-up and/or flux adjustment is allowed. CMIP2 will continue the effort started in CMIP1 to involve the international coupled modelling community in a major effort to assess the state of the art in global coupled modelling in terms of 1) documenting the mean response of the dynamically coupled climate system to a transient increase of CO2 in the models near the time of CO2 doubling, 2) quantifying, where possible, the effects of flux adjustment on climate sensitivity in the coupled simulations, and 3) documenting features of the simulated time-evolving climate system response to gradually increasing CO2. As in CMIP1, part of the motivation of CMIP2 arises from the IPCC process in that many of the global coupled models are relied on for high visibility climate change simulations. Thus it is important for the global coupled climate modelling community to undertake a comprehensive evaluation of the climate sensitivity of current global coupled models.
Initial intercomparison exercises will involve the calculation of inter-model mean and standard deviation from the transient experiments to provide an indication of the spread of coupled model climate sensitivity. Since current global coupled modelling efforts are about evenly split between flux-adjusted and non-flux adjusted simulations, the two sets of models can be compared to provide an indication of the consequences of flux adjustment on the simulation of climate sensitivity.
The fields requested are an elaboration of those from CMIP1. As in CMIP1, we have attempted to constrain the number of requested fields to a subset of all the possible fields that could be intercompared. (though this "constrained" list is fairly comprehensive, as you will note below). Thus, some individual's "favorite" fields may not appear in the list. This is not because we feel that the requested fields are the only ones of interest for comparison. By constraining the number of fields requested, we hope that the level of effort required from participating groups will be acceptable and appropriate to the task of intercomparing key quantities.
Please send your model data to Curt Covey at PCMDI in Livermore, CA (firstname.lastname@example.org; tel: 510-422-1828). For CMIP2, we have decided to recommend the procedure recently adopted for AMIP2 in terms of data submission. Groups are requested to submit their data in a format that PCMDI can readily read. The recommended format (also to be used for AMIP2) is LATS (Library for AMIP Transmission Standards). Many of you will soon (if not already) have some experience with LATS from AMIP. If not, please contact Curt and he can help you with it. If you cannot use LATS for some reason, contact Curt for instructions on what data format to use.
Please note that, as in CMIP1, CMIP2 will include a documentation of participating models, which will be prepared by the PCMDI staff. Please provide Curt with either a brief written description of your model run or a reference that describes it.
Also be aware that, as has recently been adopted for CMIP1, access to coupled model data submitted for CMIP2 will be initially accessible for analysis to members of CLIVAR NEG-2 as well as PCMDI staff. Beyond those individuals, an AMIP-style subproject procedure will be followed for others to have access to the coupled model data. That is, interested investigators will submit brief (1-2 page) summaries of proposed analyses. These summaries will be reviewed by the CMIP Panel for approval. Thus, access to model data will be controlled and all participants will be kept abreast of subproject status. If your group DOES NOT wish to have your model data made available to the subproject process, please stipulate your access requirements to Curt when you submit your data and we will honor your wishes.
(GROUPS SHOULD BE AWARE THAT, AS IN CMIP1, THERE MAY BE A SUBSEQUENT REQUEST FROM CLIVAR NEG1 FOR TIME SERIES OF MONTHLY MEAN SEA LEVEL PRESSURE, PRECIPITATION, WIND STRESS, UPPER OCEAN HEAT CONTENT, AND SST FROM THE CO2 INCREASE EXPERIMENTS SOME TIME THIS YEAR. This exercise will follow the ENSIP intercomparison, and will look at changes in ENSO statistics from the coupled models with increased CO2.)
CMIP2 STANDARD EXPERIMENT (this is required of all CMIP2 participants): 1% per year compound CO2 increase starting from present-day climate state (spin-up, flux adjustment, etc., left up to participants), 80 year experiment where CO2 doubles at about year 70.
CMIP2 ADDITIONAL FEATURES (some form of control run data is required for computing the climate changes from increased CO2; thus groups are strongly encouraged to provide the following to assist in analysis of the transient experiments): a) matching length coupled model control experiment (already submitted in many instances by groups participating in CMIP1), b) comparable equilibrium 2XCO2 mixed layer experiment (only globally averaged numbers needed-- surface air temperature difference and percent change of globally averaged precipitation--to calibrate coupled model results)
CMIP2 OPTIONS (these are not required, but if groups have this output on hand, it would be of great interest
to CMIP2): a) matching coupled model transient experiments run with and without flux adjustment; b) cloud forcing
from the control and transient coupled model experiments (clear and cloudy sky).
FOUR 20-YEAR ANNUAL MEANS of fields requested in CMIP1 plus a few additional fields, as listed below, to facilitate interpretation of the transient response (i.e. years 1-20, 21-40, 41-60, 61-80) ****TIME SERIES of several fields****
This message is being sent out to all of you on the original CMIP mailing list. Since this is an open invitation, please pass along this message to other interested individuals or groups we might have missed on our mailing list. If we don't hear from you we will leave your name on the list for all future mailings regarding CMIP. For those of you who wish to submit model data for CMIP2, please acknowledge this message and give us some indication of your interest in CMIP2 as soon as possible. WE WOULD LIKE TO RECEIVE MODEL DATA BY APRIL 1, 1997. As in CMIP1, we will do the intercomparison with a view to a workshop where results from CMIP2 will be presented, together with the latest results from your global coupled modelling efforts. Please communicate directly with Curt regarding transmission of the data. If you require a hard-copy of this solicitation letter, let me know and I can mail one out to you in conventional mail. We hope that you can participate in the ongoing CMIP exercise of assessing the state-of-the-art in global coupled climate modelling.
Gerald A. Meehl (for the CMIP Panel)