# Model Documentation

### | Version 4.0

created with goxygen 0.21.1

# 52_carbon

# Carbon (52_carbon)

## Description

The carbon module provides annual land-related CO2 emissions for the 56_ghg_policy module. The carbon module provides carbon density information on cellular level to all land modules (30_crop, 31_past, 32_forestry, 34_urban and 35_natveg), and in return it gets the current carbon stock levels from respective land pools. The module also accounts for changes in terrestrial carbon stocks cause by climate change effects on biosphere 45_climate.

## Interfaces

Interfaces to other modules

### Input

module inputs (A: normal_dec17 | B: off)
| Description | Unit | A | B
--- | --- | --- | --- | ---
pcm_land (j, land) | Land area in previous time step | \(10^6 ha\) | x |
pm_climate_class (j, clcl) | Koeppen-Geiger climate classification on the simulation cluster level | \(1\) | x |
vm_btm_cell (j, emis_source, pollutants) | Cellular emissions before technical mitigation | \(Tg/yr\) | x | x

### Output

module outputs
| Description | Unit
--- | --- | ---
fm_carbon_density (t_all, j, land, c_pools) | LPJmL carbon density for land and carbon pools | \(tC/ha\)
pm_carbon_density_ac (t, j, ac, c_pools) | Carbon density for age classes and carbon pools | \(tC/ha\)
vm_carbon_stock (j, land, c_pools) | Carbon stock in vegetation soil and litter for different land types | \(10^6 tC\)
vm_carbon_stock_reduction (j, land, c_pools) | Reduction in carbon stocks compared to previous time step | \(10^6 tC/time step\)

## Realizations

### (A) normal_dec17

This realization calculates annual land-related CO2 emissions as difference of carbon stocks between the current and the previous time step. Land-related CO2 emissions include CO2 emissions from land-use change as well as changes in carbon stocks in the terrestrial biosphere due to climate change (the later is only included if `c52_carbon_scenario = "cc"`). The realization provides carbon density information on cellular level to all land modules (30_crop, 31_past, 32_forestry, 34_urban and 35_natveg), which return land type specific carbon stocks to the carbon module. The realization also provides carbon density for different age-classes, based on a chapman-richards volume growth model, to the land modules 32_forestry and 35_natveg (Humpenöder et al. 2014).

Change of carbon stocks is calculated as a difference between the current and the previous time step.

\[\begin{multline*} v52\_carbon\_stock\_diff(j2,land,c\_pools) = pc52\_carbon\_stock(j2,land,c\_pools) - vm\_carbon\_stock(j2,land,c\_pools) \end{multline*}\] \[\begin{multline*} vm\_carbon\_stock\_reduction(j2,land,c\_pools) \geq pc52\_carbon\_stock(j2,land,c\_pools) - vm\_carbon\_stock(j2,land,c\_pools) \end{multline*}\]

Annual CO2 emissions are obtained by dividing `v52_carbon_stock_diff` by time step length (e.g. 5 or 10 years).

\[\begin{multline*} vm\_btm\_cell(j2,emis\_co2,"co2\_c") = \sum_{emis\_land(emis\_co2,land,c\_pools)}\left(\frac{ v52\_carbon\_stock\_diff(j2,land,c\_pools)}{m\_timestep\_length}\right) \end{multline*}\]

> Limitations CO2 emissions in the 1st time step (1995) are not meaningful because carbon stock information prior to 1995 is not available

### (B) off

In this realization annual land-related CO2 emissions are assumed zero.

> Limitations CO2 emissions are assumed zero

## Definitions

### Objects

module-internal objects (A: normal_dec17 | B: off)
| Description | Unit | A | B
--- | --- | --- | --- | ---
f52_growth_par (clcl, chap_par) | Parameters for chapman-richards equation | \(1\) | x |
pc52_carbon_density_start (t, j, c_pools) | Carbon density for new land in other land pool | \(tC/ha\) | x |
pc52_carbon_stock (j, land, c_pools) | Current carbon in vegetation soil and litter for different land types | \(10^6 tC\) | x | x
q52_carbon_stock_diff (j, land, c_pools) | Calculation net carbon stock change | \(10^6 tC/time step\) | x |
q52_carbon_stock_reduction (j, land, c_pools) | Calculation carbon stock reduction | \(10^6 tC/time step\) | x |
q52_co2c_emis (j, emis_co2) | Calculation of annual CO2 emissions | \(10^6 tC/yr\) | x |
v52_carbon_stock_diff (j, land, c_pools) | Change in carbon stocks compared to previous time step | \(10^6 tC/time step\) | x |

### Sets

sets in use
| description
--- | ---
chap_par | Chapman-richards parameters
clcl | climate classification types
c_pools | Carbon pools
emis_co2(emis_source_cell) | Land pool CO2 emission sources
emis_source | Emission sources
land | Land pools
pollutants(pollutants_all) | subset of pollutants_all that can be taxed
t_all | 5-year time periods
t(t_all) | Simulated time periods

## Authors

Benjamin Leon Bodirsky, Florian Humpenoeder

## See Also

10_land, 30_crop, 31_past, 32_forestry, 34_urban, 35_natveg, 39_landconversion, 45_climate, 56_ghg_policy

## References

Humpenöder, Florian, Alexander Popp, Jan Philip Dietrich, David Klein, Hermann Lotze-Campen, Markus Bonsch, Benjamin Leon Bodirsky, Isabelle Weindl, Miodrag Stevanovic, and Christoph Müller. 2014. “Investigating Afforestation and Bioenergy CCS as Climate Change Mitigation Strategies.” Environmental Research Letters 9 (6): 064029. doi:10.1088/1748-9326/9/6/064029.