Climate is made by the general circulation of the atmosphere and the global pattern of air movements. Many meteorologists believed that shifts in this pattern were the main cause of climate change.
Early in the 20th century, Vilhelm Bjerknes developed a set of seven “primitive equations” describing the behavior of heat, moisture and air motion. Lewis Richardson published a numerical system for weather prediction, using simplified versions of Bjerknes’s equations. His idea was to divide up a territory into a grid of cells, each with its own set of numbers describing air pressure, temperature and other metrics, as measured at a given hour. He would then solve equations for how air behaved. He could calculate wind speed and direction, from the difference in pressure between two adjacent cells.
In 1958, Joseph Smagorinsky and Syukuro Manabe put into their model the way rain fell on the surface and evaporated, they put in how radiation passing through the atmosphere interacted not only with water vapor but also with ozone and carbon dioxide gas (CO2), they put in how the air exchanged water and heat with simplified ocean, land, and ice surfaces, and much more.
By 1965 the group had a somewhat complete three-dimensional global model that solved the basic equations for an atmosphere divided into nine levels. It was still highly simplified, with no geography – land and ocean – were blended into a single damp surface, which exchanged moisture with the air but could not take up heat. However, the way the model moved water vapur around the planet looked very realistic. Their printouts showed a stratosphere, a zone of rising air near the equator, a subtropical band of deserts, and so on.