The carbon tax is a proposed tax on carbon dioxide emission, a pollutant that contributes to global warming. Carbon taxes would indirectly tax fossil fuels and other energy sources which emit carbon dioxide.

Increasing levels of carbon dioxide cause energy from the sun that would normally be reflected back into space to remain in the Earth's atmosphere. This can contribute to the gradual increase in the planet's temperature that is known as global warming. Because of the widespread burning of fuels that emit carbon dioxide, the carbon tax has been proposed as a possible solution.