The global average temperature last year was the ninth-warmest in the modern meteorological record, continuing a trend linked to greenhouse gases that saw nine of the 10 hottest years occurring since the year 2000, NASA scientists said on Thursday. A separate report from the U.S. National Oceanic and Atmospheric Administration (NOAA) said the average temperature for the United States in 2011 as the 23rd warmest year on record. The global average surface temperature for 2011 was 0.92 degrees F (0.51 degrees C) warmer than the mid-20th century baseline temperature, researchers at NASA's Goddard Institute for Space Studies said in a statement. The institute's temperature record began in 1880. The first 11 years of the new century were notably hotter than the middle and late 20th century, according to institute director James Hansen. The only year from the 20th century that was among the top 10 warmest years was 1998.