The Greenhouse Effect
The global warming forecast is not new, nor has it changed much over the last century. The basic physics of the greenhouse effect was described in 1827 by Jean Baptiste Joseph Fourier. Fourier was a mathematician in Bonaparte’s army in Egypt. His name is best known for the Fourier transform, a mathematical technique for separating some complicated signal (such as the history of temperature through time, to choose an apropos example) into the sum of simple waves of different frequencies (such as the day/night cycle and the annual cycle), what we call calculating a spectrum.
Fourier’s contribution to Earth science is the idea that gases in the atmosphere that absorb infrared radiation could eventually warm up the surface of the earth. He made the analogy of a greenhouse, but the actual name “greenhouse effect” came later.
The temperature of a planet is set by a natural thermostat, which balances the planet’s energy budget. Energy comes in to the Earth as sunlight and leaves as infrared. The greenhouse effect of a gas changes the outgoing part of the budget, the infrared. All objects warmer than absolute zero shine in the infrared. A hot heating element glows red that we can see; the same object at room temperature glows in the infrared.