United States scientists say the upper reaches of Earth's atmosphere are unexpectedly shrinking and cooling due to lower ultraviolet radiation from the sun.
The sun's energy output dropped to unusually low levels from 2007 - 2009, a significantly long spell with virtually no sunspots or solar storms.
During that period, the thermosphere, the altitude of which ranges from about 90km - to 500km, shrank and contracted from a sharp drop in ultraviolet radiation.
The thermosphere cooled by 41 degrees Celsius in 2008 compared to 1996, and shrank by 30%.
