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|The Discovery of Global Warming February 2011|
The general circulation of the atmosphere. Hot air rises in the tropics, moves north or south, descends and returns in the equatorial "Hadley cells". Its path along the surface is bent into the trade winds by the Earth's rotation (Coriolis Effect). Two other cells in each hemisphere work similarly. This general pattern was observed in the nineteenth century, but cannot be understood with any simple or mathematical explanation: it can only be calculated with digital computers.