at the earth's surface. 19% simply warms the atmosphere so that actually only 47% reaches the earth's surface. Of the 66% that reaches the earth's surface or is retained in its atmosphere, all becomes converted to long wavelength (terrestrial) radiation. It becomes distributed as follows: 101 units are absorbed by water vapor in the atmosphere as this radiation attempts to leave the earth. 18 units escapes to space through a narrow band of wave lengths for which water is transparent. 23 units escapes to the atmosphere as heat (evaporation, transpiration) 10 units escapes to heat the atmosphere by convection (turbulence). 105 units is retransmitted by the atmosphere back to the earth's surface as infra-red rays. 48 units escapes to space as infra-red rays. The greatest heat source at the earth's surface is the long wavelength radiation that is returned from the atmosphere. The greatest loss of heat is through the long wavelength radiation to the atmosphere from the earth's surface. The transfer of heat on the earth from an area of net heat gain (0-40° latitude) to the area of net heat loss (40°-90° latitude) occurs through air movement. Some occurs by water movement, but this is rather slight. Temperature Distribution There is decreasing temp. with increasing latitude. There are greater temp. differences in the northern hemisphere because there are greater land masses present in this hemisphere. The general circulation