In 2009 the G20 (group of 20 largest economies) agreed to work on eliminate subsides for fossil fuels. However, as noted in 2019 by the IMF, global subsidies remain large. Some subsidies are aimed at consumers - with prices below production costs in many large exporting countries. Others help producers as noted for example by Senator Grassley and Udall (D) here in the US.

You are in charge. Design a policy that gets prices of fossil fuels "right". Start by diagramming the situation that incorporates producer and consumer subsidies and private and social costs. Then articulate your policy proposal.