In order to run CMIP7 simulations, HadCM3 must be able to ingest various forcings from greenhouse gases to aerosols and natural changes. These pages document where to get CMIP forcing from and how to process it for use in HadCM3.
CMIP forcing data is kept centrally in an activity called “inputs4mips”.
There is a (long) document here with details from CMIP6: CMIP6 Forcing Datasets Summary and the database itself is here: Inputs4MIPs
It takes a bit of getting used to: you can search for example for a variable under “Classificaitons” tab, then “variable ID”. It’s probably best to know in advance exactly what you want rather than to browse. It’s not very user friendly for random exploring…
As an example, if you want GHG concentrations don’t look for “CH4” but for “mole_fraction_of_CH4_in_air”. Though note for CMIP7 data, some changes are made – they’ve simplified the variable names, e.g., for ‘mole_fraction_of_methane_in_air’, ‘ch4’ is the new variable. A full list variable name mapping could be found here CMIP7 GHG concs.
It is strongly recommended to read the document before accessing any data. Some datasets are also available elsewhere which can provide more friendly download options.
CMIP7 forcings home page, and you can have an overview here.
Currently greenhouse gases are available, guide to use is here.
Forcings availability (last updated: 14th Apr 2025):
[!NOTE] There are two categories of data for CMIP7, the
mip_erametadata value being ‘CMIP7’ and ‘CMIP6Plus’. ‘CMIP6Plus’ is used for testing, while ‘CMIP7’ is used in CMIP7 production simulations.
The following pages provide details of how to access CMIP forcings, process them into the correct format for HadCM3, and use them in a model run.
As mentioned in CMIP7_simulations, there are 3 phases we implement these forcings. Phase 1 (Single Testing Phase), we test the availability to add a single forcing; Phase 2 (Combined Testing Phase), we gradually merge various forcings; Phase 3 (CMIP7 experiments Phase), standard runs for CMIP7.
For Phase 2, we document the processes in CO2 emissions.
As CMIP7 forcing data are provided at monthly resolution, and high spatial resolution (e.g., 0.5 degree for emissions), they are quite large and could be messy. We plan to backup these forcings (rawdata, ready-to-use ancillary files) on our machines. For long-term management, we would like to create a linux user group (i.e., for CMIP7), and everyone in the group have write permission (sometimes this could be dangerous). But this needs to be properly figured out as new machines or new systems are being updated.
Currently, members responsible for forcings are suggested to have a copy of the data in their work directory. If they need to be backup up, please email either Paul, Dan or Alex to make a copy of them. FYI, the directory sits under oligocene:~swsvalde/public_html/CMIP7, which could be accessed on web at www.paleo.bristol.ac.uk/CMIP7.