To show CO₂ emissions under the "Variable" tab in LEAP, you first need to make sure that CO₂ is added as an effect. Go to the "Effects" section on the left panel, and check if CO₂ is listed under Greenhouse Gases. If not, right-click and add it. Name it CO₂, set the type as Emission, and choose the category Greenhouse Gas.

Next, go to the "Fuels" section and link CO₂ to the fuels used in your model. For each fuel (like Natural Gas or Diesel), right-click, go to Properties, then open the Environmental Loadings tab. Click Add, choose CO₂, and enter an emission factor (e.g., 56,100 kg/TJ for Natural Gas). This allows LEAP to automatically calculate emissions when that fuel is used.

After this, go to your demand branches (e.g., Residential → Cooking). Under the "Environmental Loadings" tab, you can now add CO₂ if needed, especially for technologies that don’t use standard fuels or have direct process emissions.

Once this setup is complete, LEAP will include CO₂ emissions in the results, and you’ll see CO₂ under the "Variable" tabs and in the Results > Environmental Loadings section.