In the context of this article the Arctic is defined as the area of the globe with latitudes north of 66° 33’ 39’’, the present polar circle with an obliquity of 23° 26’ (that can vary from 22° to 24° 30' during a 40 000 years cycle). The Arctic can be also defined as the isotherm of <50°F any month of the year. Both definitions mean that Arctic area is changing slowly with time.