Influence of CO2 in CESM

[lara]

Hello,
I want to find out more about how CO2 influences for example on the global temperature, and how this is reflected in the model (theoretically).
Therefore, I'm trying to find the underlying equations in the CESM1 or 2 model which depend on values/parameters related to CO2.
I've searched in the documents and descriptions provided on the CESM website, but I haven't found anything yet.
Has someone an idea how or where to find such information?
Thanks a lot for your help!

 

[erik]

We probably need several different people to chime in here because this is a very broad question that spans all model components. CO2 impacts the radiative schemes in the atmosphere model (CAM). @nusbaume could you give Lara some guidance for CAM on this?

@lara are you interested in the complete coupled system of all prognostic components (atmosphere, ocean, sea-ice, and land)? Or are you just interested in some of the components?

For the land model CO2 impacts plant growth. So for example this chapter in the CLM5.0 technical Note is relevant (for CESM2)

2.9. Stomatal Resistance and Photosynthesis — ctsm release-clm5.0 documentation

@altuntas could you comment regarding the ocean model? And @dbailey could you comment regarding sea ice?

 

[dbailey]

We do not have CO2 in the sea ice at this time.

 

[altuntas]

I am mentioning @klindsay and @mlevy who may chime in on the ocean aspect.

 

[lara]

Thank you very much for your help! I'm mostly interested in the component of the atmosphere (and also ocean)

 

[nusbaume]

Hi Lara,

The main influence of CO2 in the atmosphere is with regards to the radiative fluxes (specifically the longwave fluxes). In CAM these calculations are done using the RRTMG radiation model. A short description can be found in the CAM5 technical description (section 4.10) here:

https://www.cesm.ucar.edu/models/cesm2/atmosphere/docs/description/cam5_desc.pdf

A more complete description will likely be found in the journal references therein.

Outside of radiation my understanding is that CO2 is mostly just treated as either well-mixed (so the same values everywhere) or as an advected tracer with associated surface emissions. I imagine @klindsay would be able to provide more information on those particular aspects.

Hope that helps!

Jesse