esm-historical

The esm-historical configuration simulates the climate from 1850-2022 using a fully interactive carbon cycle and historical CO2 anthropogenic emissions data.

This configuration is used for the CMIP7 esm-historical experiment.

Info

Please note that the settings described below are implemented in the configuration and no further changes are required to run it. The descriptions below are included to aid in understanding of the configuration and to assist with making modifications.

Inputs¶

The same input files as the historical configuration are used to provide the model with time varying aerosol, ozone, nitrogen deposition, volcanic forcing, solar irradiance and land use change data.

Atmosphere¶

An additional input file provides time varying anthropogenic CO2 emissions to the atmosphere model:

CO2_fluxes_1849_2023_cmip7.anc: Gridded anthropogenic CO2 emissions in units kg(CO2) m-2 s-1.

Restart¶

The esm-historical configuration uses the restart from the esm-piControl experiment with calendar year 201. The year in the restart has been changed to 1850 for use in the esm-historical configuration.

Key settings¶

The esm-historical configuration uses the same settings as the historical configuration, with changes for activating the interactive carbon cycle and external emissions file.

The following differences are shown with respect to the historical configuration.

Greenhouse gas emissions and concentrations¶

As with the esm-piControl configuration, the following settings activate the interactive carbon cycle.

atmosphere/um_env.yaml¶

+CO2EMITS: INPUT/CO2_fluxes_1849_2023_cmip7.anc

The above setting points the model to the CO2 emissions ancillary file in the payu work directory.

atmosphere/namelists¶

- L_CO2_INTERACTIVE=.FALSE.,
- L_CO2_MASS=.FALSE.,
+ L_CO2_INTERACTIVE=.TRUE.,
+ L_CO2_MASS=.TRUE.,

To enable an external CO2 emissions file, the following lines are added:

+ L_CO2_EMITS= .TRUE.,
...
+ &UPANCA ANC_REF_NO=78, PERIOD=4, INTERVAL=1 /

The UM linearly interpolates input data supplied at monthly frequencies to higher frequencies for use during the simulation. The line &UPANCA ANC_REF_NO=78, PERIOD=4, INTERVAL=1 / controls this interpolation for the CO2 emissions ancillary file (ANC_REF_NO=78). The PERIOD setting specifies the units for the update frequency (1: years, 2: months, 3: days, 4: hours) and the INTERVAL specifies the update frequency in these units. Here, the CO2 emissions data are updated in the model via linear interpolation every 1 hour.

All other greenhouse gas concentrations are prescribed and use the same values as the historical configuration. For clarity, the specification of the CO2 concentrations is removed:

&CLMCHFCG
...
- CLIM_FCG_NYEARS = 174, 174, 174, 174, 174, 174, 174, 174, 174, 174,...
+ CLIM_FCG_NYEARS = 0, 174, 174, 174, 174, 174, 174, 174, 174, 174,...
...
- CLIM_FCG_YEARS(:,1) = 1850, 1851, 1852, 1853, 1854, 1855, 1856, 1857,...
- CLIM_FCG_LEVLS(:,1) = 4.317926e-04, 4.319855e-04, 4.321797e-04, ...

Configuration scripts¶

The esm-historical configuration uses the same land use change userscript as the historical configuration to update surface type fractions at the end of each year.