ITVCM allows the following functionality:

- Calculation of gas concentration by using input serial data of anthropogenic emissions. The greenhouse gases are: CO2, CH4, N2O, CFC 11, CFC 12, HCFC-22, HFC-1341, SF6

and PFC-14.

- Calculation of radiative forcing from gases listed above together with aerosol emissions.
- Calculation of global mean temperature.
- Calculation of global mean sea level rise.

Figure 2. Implementation diagram.

The black boxes represent the following items:

- CONCi: Concentration of gas i. There is a concentration module for each implemented gas. Gases can be: CO2, CH4, N2O, CFC11, CFC12, HCFC-22, HFC-1341, SF6.
- RFi: Radiative forcing of gas i. There is a radiative forcing for each implemented gas.
- AERO: Radiative forcing of aerosol substance.
- RFTOT: Total radiative forcing.
- TEMP: Global mean temperature.
- SLR: Global mean sea level rise.

The red boxes represent input serial data provided by the user:

- Ei: Gas emission.
- RFi: Radiative forcing of gas
- Ci: Gas concentration.
- RFv: Radiative forcing due to volcano activity.
- RFo: Radiative forcing due to other gases that are not included in the software.
- RFt: Total radiative forcing.
- RFaer: Radiative forcing due to aerosol substances.
- ECO2: Anthropogenic CO2 emission.
- T: Input temperature vector.

Figure 3. 203 gases implementation diagram

There are 203 gases described on gaspar.xls with structure more simplified than CO2, CH4 and N2O gases. For these gases, CONC and RF modules are unified, as we see on figure 3.

Diagrams

The diagrams on figures 2 and 3 show the calculation flow in a specific period. Equation coefficients are calculated together with their state variables, which are resolved with Runge-Kutta method. Other methods which were implemented for ordinary differential equations (ODEs) were Euler method and Runge-Kutta fourth-order method (RK4). The iterationType parameter has 'euler' and 'RK4' options to choose. The order of the iterative Runge-Kutta method indicates the error order (according to its expansion in Taylor's series) and how many evaluations about the function will be done in each step.

Figure 4 represents the difference between the temperatures seen on Euler and RK4 methods. The temperature differences between the years 1750 and 2100 is bigger than 3oC. The values difference between the same methods is always smaller than 0.01oC, which indicates a difference smaller than 0.33% between the methods.

Figure 4. Difference between the temperatures calculated on Euler and RK4 methods.