Ehrlich and Holdren first proposed global warming as an environmental threat in 1971, but the issue did not gain much attention by the scientific community until the mid-1980s. Satellite data became available at the same time that computing advances permitted mathematical models to be used to study the earth's climate. The leader in this new branch of science is Dr. Stephen Schneider from the National Center for Atmospheric Research in Boulder Colorado. The basic idea behind global warming goes back to the energy balance of incoming solar radiation. Remember that the earth exists in a state of thermal equilibrium with space, where the energy of incoming radiation equals the energy re-radiated back into space.
Incoming radiation is primarily short wavelength, ultraviolet light.
Absorption, scattering, and emission processes change the wavelength of the incoming light to photons with less energy, and therefore a longer wavelength. The energy re-radiated back into space contains fewer short wavelength photons and a greater number of longer wavelength photons. These longer wavelength photons come from the visible and infrared portions of the electromagnetic spectrum. Any substance that would absorb these longer wavelength photons would have the effect of decreasing the energy released to space, leading to higher temperatures at the earth's surface. Nitrogen oxides, CFCs and HCFCs are also important greenhouse gases.