Global warming refers to the increase in the planet’s overall average temperature in recent decades. Natural processes have always affected Earth’s temperature and climate, but more recently, the planet’s temperature and climate have changed at a higher pace than nature alone can explain. These rapid changes are due to human activities and the widespread use of fossil fuels for energy.

Fossil fuels include coal, oil and natural gas. Burning fossil fuels causes what is known as the “greenhouse effect” in Earth’s atmosphere. The greenhouse effect happens when the sun’s rays penetrate the atmosphere, and the Earth’s surface reflects that heat. Some of the gasses in the atmosphere then trap heat over Earth. Gasses emitted by the burning of fossil fuels are very good at trapping heat and preventing it from leaving the atmosphere. These greenhouse gasses are carbon dioxide, methane, nitrous oxide, chlorofluorocarbons and water vapor. The excess heat in the atmosphere has caused the planet’s average global temperature to rise over time, otherwise known as global warming.