Dear Chris, All,
I think I should start by explaining some context for the benefit of those on this list that are not familiar with CMIP or the CMIP6 Data Request.
Chris is leading an international science team (C4MIP<
http://www.c4mip.net>) that is participating in the CMIP6 model intercomparison project, as one of over 20 science teams. It has been decided, at quite a high level, based on positive experience in previous CMIP projects, that data should be archived in CF compliant netcdf files, and I have the dubious honour of coordinating the effort to specify CF compliant netCDF metadata for all the data which will be archived. The document which specifies this metadata for each variable is the "Data Request" which Chris refers to.
C4MIP deals, among other things, with emissions of greenhouse gasses. In order to minimise the widespread confusion between amounts expressed in terms of (a) mass of carbon in carbon dioxide and (b) mass of carbon dioxide itself, the C4MIP community has taken to expressing quantities in units of "kgC ...." when mass of carbon is intended. Hence Chris's request for this unit to be admissible in the CF Convention (which is a requirement for having it in the Data Request).
I don't support this approach myself, but as I have already shared my views with Chris, it would be interesting now to hear what others on the list think,
regards,
Martin
________________________________
From: CF-metadata <cf-metadata-bounces at cgd.ucar.edu> on behalf of Jones, Chris D <chris.d.jones at metoffice.gov.uk>
Sent: 31 January 2019 09:38
To: cf-metadata at cgd.ucar.edu
Subject: [CF-metadata] CMIP6 Confusion regarding carbon flux units
Dear Martin, dear All,
it is emerging that groups are making errors in implementing the carbon cycle data requests - especially regarding the units of carbon fluxes.
The issue is confusion over whether to report kg of CARBON or kg of CO2.
The intended correct answer is buried deep within the long name, where fluxes are described as, ??. flux of CO2 expressed as carbon ??. But unless you know where to look this is rather hidden and is resulting in groups mixing units of carbon and CO2 across variables.
So this is a request - actually a plea - that we revisit the decision to include the quantity in the units definition. I have heard the arguments that ?kg C? is not an SI unit and we just need to explain it in the long name - but this is really not working and is causing real confusion and errors.
So PLEASE, PLEASE, can we re-define the labels for carbon fluxes and stores in terms of ?kgC m-2 s-1? etc. ?
There has been such a massive effort to both define and implement this data request it would be a huge shame if substantial errors came in at the last minute - this small change will prevent that.
thanks,
Chris
--
Dr Chris Jones
Head, Earth System and Mitigation Science Team
Met Office Hadley Centre, FitzRoy Road, Exeter, EX1 3PB, U.K.
Tel: +44 (0)1392 884514 Fax: +44 (0)1392 885681
E-mail: chris.d.jones at metoffice.gov.uk http://www.metoffice.gov.uk<http://www.metoffice.gov.uk/>
Received on Thu Jan 31 2019 - 05:27:36 GMT
