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.