I’m attending a workshop this week in which some of the initial results from the Fifth Coupled Model Intercomparison Project (CMIP5) will be presented. CMIP5 will form a key part of the next IPCC assessment report – it’s a coordinated set of experiments on the global climate models built by labs around the world. The experiments include hindcasts to compare model skill on pre-industrial and 20th Century climate, projections into the future for 100 and 300 years, shorter term decadal projections, paleoclimate studies, plus lots of other experiments that probe specific processes in the models. (For more explanation, see the post I wrote on the design of the experiments for CMIP5 back in September).

I’ve been looking at some of the data for the past CMIP exercises. CMIP1 originally consisted of one experiment – a control run with fixed forcings. The idea was to compare how each of the models simulates a stable climate. CMIP2 included two experiments, a control run like CMIP1, and a climate change scenario in which CO2 levels were increased by 1% per year. CMIP3 then built on these projects with a much broader set of experiments, and formed a key input to the IPCC Fourth Assessment Report.

There was no CMIP4, as the numbers were resynchronised to match the IPCC report numbers (also there was a thing called the Coupled Carbon Cycle Climate Model Intercomparison Project, which was nicknamed┬áC4MIP, so it’s probably just as well!), so CMIP5 will feed into the fifth assessment report.

So here’s what I have found so far on the vital statistics of each project. Feel free to correct my numbers and help me to fill in the gaps!

(1996 onwards)
(1997 onwards)
Number of Experiments 1 2 12 110
Centres Participating 16 18 15 24
# of Distinct Models 19 24 21 45
# of Runs (Models X Expts) 19 48 211 841
Total Dataset Size 1 Gigabyte 500 Gigabyte 36 TeraByte 3.3 PetaByte
Total Downloads from archive ?? ?? 1.2 PetaByte
Number of Papers Published 47 595
Users ?? ?? 6700

[Update:] I’ve added a row for number of runs, i.e. the sum of the number of experiments run on each model (in CMIP3 and CMIP5, centres were able to pick a subset of the experiments to run, so you can’t just multiply models and experiments to get the number of runs). Also, I ought to calculate the total number of simulated years that represents (If a centre did all the CMIP5 experiments, I figure it would result in at least 12,000 simulated years).

Oh, one more datapoint from this week. We came up with an estimate that by 2020, each individual experiment will generate an Exabyte of data. I’ll explain how we got this number once we’ve given the calculations a bit more of a thorough checking over.


  1. Very cool! At UVic, I am helping out with the EMIC version of CMIP5 – we have 13 models participating and about 50 experiments. The models are much simpler than GCMs, and have a very wide range of complexity and resolution, but all of them can run for several thousand years without a problem. I will be blogging about this soon.

  2. @Kate
    Actually, that’s 14 models – forgot to count the UVic one ­čÖé
    You can read more about the intercomparison here: http://climate.uvic.ca/EMICAR5/

  3. Hi Steve

    Interesting stuff, cheers.

    Would’ve loved to go to the CMIP5 workshop but was busy elsewhere. I don’t suppose you know if titles/abstracts are online anywhere?

  4. Pingback: What is Climate Informatics? | Serendipity

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