Global warming begins with the greenhouse effect, which is caused by the interaction between Earth's atmosphere and incoming radiation from the sun. "The basic physics of the greenhouse effect were figured out more than a hundred years ago by a smart guy using only pencil and paper (Svante Arrhenius in 1896)," Josef Werne, an associate professor in the department of geology and planetary science at the University of Pittsburgh, told Live Science.
Solar radiation passes through the atmosphere to the surface of Earth, where it is absorbed and then radiated upward as heat. Gases in Earth's atmosphere absorb about 90 percent of this heat and radiate it back to the surface, which is warmed to a life-supporting average of 59 F (15 C). This very helpful process is called the greenhouse effect.