The fossils are referred to as those plants and animals that were buried on earth millions of years back and the fuels that are obtained from them are known as fossil fuels.
These fossil fuels are mostly comprised of elements such as carbon, nitrogen, and hydrogen. The burning up of these fossils emits a large amount of carbon that is harmful to the atmosphere. These fossils are very widely used in today's world. A small increase in the amount of carbon leads to an increase in the global surface temperature of the earth.
Thus, extensive and continued burning of fossil fuel will lead to the rising temperature of the earth.