Clime


The climes in classical Greco-Roman geography and astronomy were the divisions of the inhabited portion of the spherical Earth by geographic latitude.
Starting with Aristotle, the Earth was divided into five zones, assuming two frigid climes 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 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 are derived from the historical concept of climata.

Ptolemy

gives a list of parallels, starting with the equator, and proceeding north at intervals, chosen so that the longest day 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 to 48°32' N.
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, 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 of the full system of climes; the reduced system of seven climes is indicated by additional numbers in brackets :
parallelclimalatitudelongest daylightlocation
1.0°12 hours
2.4°4' N12:15Taprobana
3.8°25' N12:30Avalites
4.12°00' N12:45bay of Adulis
5.I16°27' N13:00Meroe island
6.20°14' N13:15Napaton
7.II23°51' N13:30Syene
8.27°12' N13:45Thebes
9.III30°22' N14:00Lower Egypt
10.33°18' N14:15Phoenicia
11.IV36°00' N14:30Rhodes
12.38°35' N14:45Smyrna
13.V40°56' N15:00Hellespont
14.43°04' N15:15Massalia
15.VI45°01' N15:30the middle of the Euxine Sea
16.46°51' N15:45Istros
17.VII48°32' N16:00the mouths of Borysthenes
18.50°04' N16:15Maeotian Lake
19.51°06' N16:30the southern shore of Britannia
20.52°50' N16:45mouths of the Rhine
21.54°1'17:00mouths of the Tanais river
22.55° N17:15Brigantion in Britannia
23.56° N17:30the middle of Great Britain
24.57° N17:45Katouraktonion in Britannia
25.58° N18:00the southern part of Britannia Minor
26.59° N18:30the middle part of Britannia Minor
27.61° N19:00the northern part of Britannia Minor
28.62° N19:30Ebudes island
29.63° N20 hoursThule
30.64°30' N21 hoursunknown Scythians
31.65°30' N22 hours
32.66° N23 hours
33.66°8'40"N24 hourspolar circle
69°30' N2 months
78°20' N4 months
39.90° N6 months