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The climes (singular clime; also clima, plural climata, from Greek κλίμα klima, plural κλίματα klimata, meaning "inclination" or "slope") in classical Greco-Roman geography and astronomy were the divisions of the inhabited portion of the spherical Earth by geographic latitude.
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Starting with Aristotle (Meteorology 2.5,362a32), the Earth was divided into five zones, assuming two frigid climes (the arctic and antarctic) around the poles, an uninhabitable torrid clime near the equator, and two temperate climes between the frigid and the torrid ones. Different lists of climata were in use in Hellenistic and Roman time. Claudius Ptolemy was the first ancient scientist known to have devised the so-called system of seven climes (Almagest 2.12) which, due to his authority, became one of the canonical elements of late antique, medieval European and Arab geography. In Medieval Europe, the climes for 15 and 18 hours were used to calculate the changing length of daylight through the year.
The modern concept of climate and the related term clime are derived from the historical concept of climata.
Ptolemy
Ptolemy gives a list of parallels, starting with the equator, and proceeding north at intervals, chosen so that the longest day (summer solstice) increases in steps of a quarter of an hour from 12 hours at the equator to 18 hours at 58° N, and then, in larger steps, to 24 hours at the arctic circle.
But for the purposes of his geographical tables, Ptolemy reduces this list to eleven parallels, dividing the area between the equator and 54°1' N into ten segments, at half-hour intervals reaching from 12 hours to 17 hours. Even later in his work, he reduces this to seven parallels, reaching from 16°27' N (13 hours) to 48°32' N (16 hours).
Ptolemy's system of seven climes was primarily adopted in Arabo-Persian astronomy, by authors such as al-Biruni and al-Idrisi, and eventually by al-Razi, the author of the 16th-century haft iqlīm ("seven climes"), while in Europe, Aristotle's system of five climes was more successful. This view dominated in medieval Europe, and existence and inhabitability of the Southern temperate zone, the antipodes, was a matter of dispute.
Thirty-nine parallels
To identify the parallels delineating his climes, Ptolemy gives a geographical location through which they pass. The following is a list of the 33 parallels between the equator and the polar circle (39 parallels between the equator and the pole: ) of the full system of climes; the reduced system of seven climes is indicated by additional numbers in brackets (note that the latitudes are the ones given by Ptolemy, not the modern exact values):