NASA’s analysis of Earth’s surface temperature found that 2012 ranked
as the ninth-warmest year since 1880. NASA scientists at the Goddard
Institute for Space Studies (GISS) compare the average global
temperature each year to the average from 1951 to 1980. This 30-year
period provides a baseline from which to measure the warming Earth has
experienced due to increasing atmospheric levels of heat-trapping
greenhouse gases. While 2012 was the ninth-warmest year on record, all
10 of the warmest years in the GISS analysis have occurred since 1998,
continuing a trend of temperatures well above the mid-20th century
average. The record dates back to 1880 because that is when there were
enough meteorological stations around the world to provide global
temperature data.
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