Disadvantages of fossil fuels include contributions to global warming, environmental pollution and their finite supply. Fossil fuels, which include coal, oil and natural gas, are the primary source of energy in the United States, accounting for 85 percent of the country's fuel usage, as of 2014.
Global warming is one of the most destructive effects of fossil fuels. When fossil fuels are burned, carbon dioxide is released, which traps heat in Earth's atmosphere and contributes to global warming. Fossil fuels have caused carbon dioxide levels in the atmosphere to rise by more than 25 percent over the past 150 years.
Fossil fuels are also a significant source of air pollution, producing pollutants, such as nitrogen oxides, carbon monoxide, hydrocarbons and sulfur oxides. Carbon monoxide is a by-product of the combustion of fossil fuels, which occurs primarily due to the use of automobiles. The extraction, production and transportation of fossil fuels can also cause significant land and water pollution. Oil spills, for example, can wreak havoc on ocean habitats and marine life, while coal mining can contribute to river pollution.
Finally, fossil fuels are non-renewable resources, meaning that their supply is limited and they will eventually cease to exist. Fossil fuel scarcity could cause huge economic and social problems in the future.