We have two direct ways of discouraging or encouraging the use of fossil fuels. They appear to have different final temperature results and they also seem to work independently of each other: if you set a carbon tax, coal oil and gas remain unchanged.
Both make the use of fossil fuels less attractive due to adding the true cost of using them to their respective prices. However if you reduce subsidies to zero for Coal, Oil, and Gas you get a higher ending temperature than setting a very high Carbon Tax.
What were the design decisions the team made in offering a set of specific controls for Coal, Oil, and Gas and which scenarios were they trying to address?
I assume that the designers had CCL in mind when adding a Carbon Tax control, though Cap and Trade are also included there?