<Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (October 2010) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (October 2010) (Learn how and when to remove this template message) </Td> </Tr> <P> The stratosphere (/ ˈstrætəˌsfɪər, - toʊ - /) is the second major layer of Earth's atmosphere, just above the troposphere, and below the mesosphere . About 20% of the atmosphere's mass is contained in the stratosphere . The stratosphere is stratified in temperature, with warmer layers higher and cooler layers closer to the Earth . The increase of temperature with altitude is a result of the absorption of the Sun's ultraviolet radiation by the ozone layer . This is in contrast to the troposphere, near the Earth's surface, where temperature decreases with altitude . The border between the troposphere and stratosphere, the tropopause, marks where this temperature inversion begins . Near the equator, the stratosphere starts at 18 km (59,000 ft; 11 mi); at mid latitudes, it starts at 10--13 km (33,000--43,000 ft; 6.2--8.1 mi) and ends at 50 km (160,000 ft; 31 mi); at the poles, it starts at about 8 km (26,000 ft; 5.0 mi). Temperatures vary within the stratosphere with the seasons, in particular with the polar night (winter). The greatest variation of temperature takes place over the poles in the lower stratosphere; variations at lower latitudes and higher altitudes are smaller . </P>

What is the height of the atmosphere in miles