Retreat of glaciers since 1850 doing so due to transient local weather conditions, which have brought more precipitation and cloudier, cooler summers since 2002. Tropical glaciers are located between the Tropic of Cancer and the Tropic of Capricorn, in the region that lies 23° 26′ 22″ north or south of the equator. Strictly, a tropical glacier is located within the astronomical tropics; the area where the annual temperature variation is less than the daily variation, and is within the oscillation area of the Intertropical Convergence Zone. Tropical glaciers are the most uncommon of all glaciers for a variety of reasons. Firstly, the regions are the
Regio Patalis the habitability of lands under the Torrid Zone and Tropic of Capricorn, D'Ailly drew on the "Opus Majus", written around the year 1267 English monk and scholar Roger Bacon. With regard to the "Regio Patalis," Bacon said: “the southern frontier of India reaches the Tropic of Capricorn near the Region of Patale and the neighbouring lands which are washed by a great arm of the sea flowing from the Ocean”. Patala was on or just south of the Tropic of Cancer, not south of the Equator, but somehow Roger Bacon had confused the Tropic of Capricorn with the Tropic of