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Solar radiation has a lower intensity in polar regions because it travels a longer distance through the atmosphere, and is spread across a larger surface area.

Regions with a polar climate are characterized by a lack of warm summers (specifically, no month having an average temperature of 10 °C or higher).

There are two distinct types of polar climate. The less severe of the two is the tundra climate, where at least one month has an average temperature of above freezing, while the colder one — known by various names including the "ice cap climate" and the "perpetual frost climate" — features sub-freezing average temperatures year-round.

Polar climates result in the absence of trees in such places, which may also be covered with glaciers or a permanent or semi-permanent layer of ice.

On Earth, the only continent where the extreme (EF -- ice cap) polar climate is predominant is Antarctica. All but a few isolated coastal areas on the island of Greenland also have the extreme EF polar climate. Such coastal regions of Antarctica and Greenland that do not have permanent ice sheets have "only" the less extreme tundra (ET) climates.

The northernmost part of the Eurasian land mass, from the extreme northeastern coast of Scandinavia and eastwards to the Bering Strait, large areas of northern Siberia and Northern Iceland have tundra climate as well. Large areas in northern Canada and northern Alaska have tundra climate, changing to ice cap climate in the most northern parts of Canada. Southernmost South America (Tierra del Fuego where it abuts the Drake Passage and such subantarctic islands such as the South Shetland Islands and the Falkland Islands have ET, or tundra climates of slight thermal range in which no month is as warm as 10°C. These subantarctic lowlands are to be found more equatorward than the coastal tundras of the Arctic basin.

In other parts of the world, many mountains have a climate where no month having an average temperature of 10 °C or higher, but as this is due to elevation, this climate is referred to as Alpine climate. Polar climates have also been observed on other planets, such as Mars, which has noticeable ice caps on both poles.

• Arctic
• Climate of Antarctica

• NOAA State of the Arctic Report 2006