Global warming is commonly referred to as an increase in the temperature of the lowest layers of Earth 's atmosphere. Global warming has occurred in the distant past as the result of natural influences, but the term is most often used to refer to the warming predicted to occur as a result of increased emissions of greenhouse gases. Primary greenhouse gases include water vapor, carbon dioxide, methane, nitrous oxide, and ozone. Carbon dioxide, as well as other greenhouse gases, is a very important factor in the vital cycles which sustain life on this planet. Plants use carbon dioxide in photosynthesis and release the oxygen necessary to maintain the lives of animal species, who through exhaling return carbon dioxide in atmosphere, completing the cycle. This is known as the greenhouse effect which is a natural process that made life on Earth
References: Baird, S. (2005). Global Warming: If You Can 't Stand the Heat. Technology Teacher, 65(3), 13-167. Easterbrook, G. (2007). GLOBAL WARMING: Who Loses--and Who Wins? (Cover story). Atlantic Monthly (1072-7825), 299(3), 52-64. Leiserowitz, A. (2004). Before and After The Day After Tomorrow. (Cover story). Environment, 46(9), 22-37. Miller, Jr., G.T. (2007). Climate Change and Ozone Depletion. In Living in the Environment. (pp. 464-491). Toronto, Canada: Thomson Learning, Inc. Sarewitz, D., & Pielke Jr., R. (2000). Breaking the Global-Warming GRIDLOCK. Atlantic Monthly (1072-7825), 286(1), 54. Schweiger, L. (2007). Global Warming Endangers Wildlife. National Wildlife, 45(3), 9-9.