Maps of Earth's outgoing mid-infrared radiation. Average over the period 18:00–21:00 UT of 1987 July 1 (a) and 2001 July 1 (b) together with the subsolar point and the terminator at the mean time. At that time the brighter regions of the Earth correspond to the deserts of Sahara, Arabian Peninsula, Atacama, and Arizona. Average over the months 1987 July (c) and 2001 July (d). Average over the years 1987 (e) and 2001 (f).