The Physical Science of Climate Change

The greenhouse effect is a natural physical process by which certain atmospheric gases absorb and re-emit infrared radiation, trapping heat that would otherwise escape to space and keeping the planet roughly 33°C warmer than it would be without an atmosphere. The basic mechanism was first outlined by the French mathematician Joseph Fourier in 1824, who recognized that the atmosphere retains heat, and was refined by the Irish physicist John Tyndall in 1859, who experimentally identified water vapor and carbon dioxide as the gases responsible for this absorption. In 1896, the Swedish chemist Svante Arrhenius produced the first quantitative estimate of how much the planet would warm if atmospheric carbon dioxide concentrations doubled, a calculation that remains conceptually close to modern estimates. The key greenhouse gases include carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and water vapor, each differing in atmospheric lifetime and in its capacity to trap heat, commonly expressed as radiative forcing measured in watts per square meter.