# Carbon module (52_carbon)¶

## Description¶

The carbon module calculates the $CO_2$ emissions before technical mitigation from changing terrestrial carbon stocks. It uses the carbon stocks of the different land modules (30_crop, 31_pasture, 32_forestry, 33_forest, 34_urban, 35_other) to estimate these emissions (yet without any technical mitigation). The emission estimates can then used by the 57_maccs module to calculate the emissions after technical mitigation and impose costs that go into the goal function. The module also provides carbon density information on cellular level for all land pools in the model.

## Interfaces¶

### Input¶

Name Description Unit A B
$sm\_years$ length of current time step years x

The last columns of the table indicate the usage in the different realizations (numbered with capital letters)

### Output¶

Name Description Unit
$vm\_carbon\_stock(j,land,c\_pools)$ carbon in vegetation soil and litter for different land types Mio tC
$vm\_btm\_cell(j,emis\_cell)$ annual emissions by emission source categories Tg N2O-N CH4 and CO2-C per year
$fm\_carbon\_density(t\_all,j,land,c\_pools)$ LPJ carbon density for land and carbon pools tC/ha

### Interface plot¶

Figure 0: Information exchange among modules

## Realizations¶

### (A) off¶

Fixes all carbon stocks for all land types to zero and sets annual $CO_2$ emissions to zero:

$vm\_carbon\_stock.fx(j,land,c\_pools)=0$
$vm\_btm\_cell.fx(j,emis\_co2\_land) = 0$

Carbon density for land and carbon pools is read-in and provided to other modules ($fm\_carbon\_density$). This information is on cellular level and is obtained from the LPJmL model.

Limitations
vm_carbon_stocks set to zero for all carbon pools.
vm_btm_cell set to zero for carbon.

### (B) normal (default)¶

Calculates annual $CO_2$ emissions on cellular level. The calculation is based on the difference in land- and carbon pool specific carbon stocks between the previous and the current time step. To obtain annual $CO_2$ emissions this difference is divided by the time step length.

\begin{align}
vm\_btm\_cell(j,emis\_co2\_land) &= \sum \limits_{emis\_co2\_to\_land(emis\_co2\_land,land,c\_pools)} [pc52\_carbon\_stock(j,land,c\_pools)\\
& - vm\_carbon\_stock(j,land,c\_pools)]/sm\_years
\end{align}

Carbon density for land and carbon pools is read-in and provided to other modules ($fm\_carbon\_density$). This information is on cellular level and is obtained from the LPJmL model.

Limitations
There are currently no known limitations of this realization.

## Definitions¶

Name Description Unit A B
$pc52\_carbon\_stock(j,land,c\_pools)$ Current carbon stock for different land types mio tC x

The last columns of the table indicate the usage in the different realizations (numbered with capital letters)

## Developer(s)¶

Benjamin Leon Bodirsky, Florian Humpenöder