Issue #3838 offers to include a diagnostic for the climatology of surface concentrations of trace gases (CH4, CO2, N2O). In order to implement and test the diagnostic, the surface flask observations from NOAA's Global Monitoring Lab need to be cmorized and added to ESMValTool observational datasets (Tier 2).

The work done in this issue will implement a downloader and a formatter for the station surface concentrations of CO2, CH4 and N2O for #3838.

Parts of the cmorization of the datasets rely on code developed in #3227 since the modality and structure of the datasets are similar. A common formatting framework is developed for all three trace gases using an attribute in the dataset recipe to call a general formatting function to maximise the use of common functions.

Branch and pull request
Work ongoing by jlenh (me), current branch state in branch noaa_gml_surface_flask_trace_gases_cmorizer (not pushed yet, problems with access rights as contributor?)