What are fossil fuels?

Fossil fuels are materials formed naturally in the Earth's crust from the remains of dead plants and animals over millennia. They are extracted and used chiefly for fuelling purposes.

According to the United Nations, over 80% of the CO₂ generated by humans comes from burning fossil fuels. Their extraction, combustion and consequent emissions-to-air negatively affect the carbon cycle, which in balanced states allows for climate stability and a functioning biosphere. Fossil fuels include but are not limited to petroleum, coal, and natural gas.