Information about cH4 concentrations in NorESM2-LM

[oyvindseland]

From noresm-ncc

I'm a postdoc at McGill University trying to develop statistical tools for modelling how gas and aerosol concentrations impact sea-surface temperatures.

For different scenarios (ssp126, ssp245, ssp370), I found on ESGF the variables representing the concentration maps of different gases and aerosols (CO2, BC, SO2) at the different atmospheric levels.

However, for CH4, I'm only finding two variables (ch4global and wetlandCH4). The first one represents the global mean of CH4, and not the CH4 concentration map (i.e. CH4 at all locations + levels).

I was wondering if NorESM only represents CH4 as a global mean, or if some variables might be missing or labelled differently?

Thank you very much,

Julien Boussard

[oyvindseland]

The CH4 surface concentration is a global mean. In addition there is an assumed vertical profile taken. I think the latter is from a explicit methane concentration wih WACCM at NCAR. Pinging Dirk Olivie for more details. @DirkOlivie

[julienboussard]

Thank you, I will use the global mean then. By "there is an assumed vertical profile taken", do you mean that there should be a vertical profile for the global mean, or that the mean is taken with respect to a given vertical profile?

@DirkOlivie if there's a way to access the explicit methane concentration wih WACCM at NCAR, I would be very interested to do that.

[JorgSchwinger]

Regarding CO2, this is also represented as a global mean value in the concentration-driven SPP scenarios in NorESM2. If you have found a spatially resolved atmospheric CO2 concentration for these scenarios on ESGF, these should not been used (didn't we retract them?). Please use the global mean CO2 concentrations as given by the scenario specifications.

[julienboussard]

Thank you very much for your reply!

For CO2, I found multiple variables, including co2 which is a map of co2 concentrations (not a global mean), and co2mass which is the Total Atmospheric Mass of CO2. Given what you've told me I should use co2mass for the concentration-driven SPP scenarios in NorESM2?

Also, following up on that, how do I distinguish emission-driven from concentration-driven scenarios?
ssp245 will be emissions driven? what about esm-ssp245? Additionally, in the emission-driven scenarios, is it correct that the variable co2 reflect the concentration of co2 in the atmosphere?

[JorgSchwinger]

Simulations starting with esm-ssp are emission-driven, otherwise, they are concentration-driven. For the latter the variable co2 is incorrect (and I think we should have retracted it). co2mass should be okay for the concentration-driven simulations, but please double check that it looks reasonable.

And yes, in the emission-driven simulations co2 is the 3d-distribution of CO2 in the atmosphere.