2012 was among Earth's 10 Warmest Years on Record, Says NASA

The year 2012 was one of the 10 warmest years on record since 1880, NASA scientists announced Tuesday.

According to an analysis made by NASA's Goddard Institute for Space Studies (GISS), all 10 of the warmest years occurred since 1998, showing a continuing trend of temperatures well above the mid-20th century average.

The new analysis showed that the average global temperature has risen about 1.4 degrees F (0.8 C) since 1880. Last year's average temperature was about 58.3 degrees Fahrenheit, which is 1.0 F (0.6 C) warmer than the mid-20th century average.

According to scientists, the increase in greenhouse gas levels in the Earth's atmosphere has triggered a significant long-term rise in global temperatures.

With the increase in greenhouse gases, each successive year will not necessarily be warmer than the year before, but each successive decade will likely be hotter than the previous decade, said the scientists.

"One more year of numbers isn't in itself significant," GISS climatologist Gavin Schmidt said in a statement. "What matters is this decade is warmer than the last decade, and that decade was warmer than the decade before. The planet is warming. The reason it's warming is because we are pumping increasing amounts of carbon dioxide into the atmosphere."

Carbon dioxide is one of the primary greenhouse gases responsible for the increase in global temperatures. The gas is present naturally in the atmosphere, but emission levels have increased due to human activities such as burning of fossil fuels.

The level of carbon dioxide in the atmosphere was 315 parts per million in 1960, but the measurements have exceeded 390 parts per million recently.

While the globe experienced a warm year in 2012, it was the hottest year on record in the contiguous United States. The average temperature last year in the lower 48 states (excluding Alaska and Hawaii) was 55.3°F, which was 3.2°F above the average temperatures in the 20th century and 1.0°F above the previous record set in 1998, according to a report by the National Oceanic and Atmospheric Administration (NOAA).