NorESM3.0 emission driven : incorrect CO2 in radiation call

[DirkOlivie]

What happened?

The recent CO2 emission-driven simulation still use prescribed CO2 concentrations in the radiation calculation. This was the case for the simulations :

• nHISTesm.ne16pg3_tn14.noresm3_0_beta03b.2025-11-04
• nhistesm.ne16pg3_tn14.noresm3_0_beta19.Base_i446F.Olivia.2026-06-09
• n1850esm.ne16pg3_tn14.pr-noresm3_0_beta19.Base_i446F.Olivia.2026-06-07

The first one can be found on Betzy in the directory :

• /cluster/projects/nn9560k/tjiputra/NorESM/NorESM3_dev_cases/nHISTesm.ne16pg3_tn14.noresm3_0_beta03b.2025-11-04

The last two can both be found on Olivia in the directories :

• /cluster/projects/nn9560k/adagj/NorESM/cases-noresm3dev/nhistesm.ne16pg3_tn14.noresm3_0_beta19.Base_i446F.Olivia.2026-06-09
• /cluster/projects/nn9560k/adagj/NorESM/cases-noresm3dev/n1850esm.ne16pg3_tn14.pr-noresm3_0_beta19.Base_i446F.Olivia.2026-06-07

Prescribed CO2 concentrations are still read by the model (this is in principle not a problem). This can be seen in atm_in :

flbc_list              = 'CO2','CH4','N2O','CFC11','CFC12','CFC11eq'

The problem is that these prescribed CO2 concentrations are used in the radiation calculation. This can be seen in atm_in :

rad_climate            = 'A:Q:H2O', 'N:O2:O2', 'N:CO2:CO2', 'N:ozone:O3', 'N:N2O:N2O', 'N:CH4:CH4', 'N:CFC11:CFC11', 'N:CFC12:CFC12'

N means that prescribed values are used, A means that a 3D field is used. This should have contained instead :

'A:CO2:CO2'

What are the steps to reproduce the bug?

See the 3 experiments mentioned above. The corresponding simulation issue numbers are 266, 453 and 451.

What CAM-Nor tag were you using?

noresm3_0_039_cam6_4_121

What machine were you running CAM (or NorESM) on?

Olivia

What compiler were you using?

Intel

Path to a case directory, if applicable

The first one can be found on Betzy in the directory : - /cluster/projects/nn9560k/tjiputra/NorESM/NorESM3_dev_cases/nHISTesm.ne16pg3_tn14.noresm3_0_beta03b.2025-11-04 The last two can both be found on Olivia in the directories : - /cluster/projects/nn9560k/adagj/NorESM/cases-noresm3dev/nhistesm.ne16pg3_tn14.noresm3_0_beta19.Base_i446F.Olivia.2026-06-09 - /cluster/projects/nn9560k/adagj/NorESM/cases-noresm3dev/n1850esm.ne16pg3_tn14.pr-noresm3_0_beta19.Base_i446F.Olivia.2026-06-07

Will you be addressing this bug yourself?

No

Extra info

I intend to run two short simulations where I output the CO2 concentration seen by the radiation code (m_CO2_c and cb_CO2_c variables). That should confirm which CO2 field (the prescribed or the interactively calculated one) is taken into account for the radiation calculation.

[DirkOlivie]

Hi @gold2718

I assume it is related to the lines in buildnamelist :

elsif (($co2_cycle and !$co2_cycle_rad_passive) or ($chem =~ /ghg_mam4/) or ($chem =~ /ghg_mam_oslo/)) {
    $radval .= ",'N:O2:O2','A:CO2:CO2'";
}   
else { 
    $radval .= ",'N:O2:O2','N:CO2:CO2'";

Maybe co2_cycle and co2_cycle_rad_passive are different from what we expect.

[DirkOlivie]

Hi @gold2718 possibly build-namelist is working well. However in all NorESM use-cases (1850_camnor_lt_osloaero.xml, hist_camnor_lt_osloaero.xml, ...) we have hardcoded a line

<rad_climate>'A:Q:H2O','N:O2:O2','N:CO2:CO2','N:ozone:O3','N:N2O:N2O','N:CH4:CH4','N:CFC11:CFC11','N:CFC12:CFC12'</rad_climate>

Maybe we should remove that line from the use-cases, test whether build-namelist works well, and see whether we obtain the correct atm_in.

[gold2718]

@DirkOlivie, Is this resolved by #291?