NASA announced this week that 2012 was the ninth warmest year since 1880, the earliest date to which global temperatures can be tracked. 2005 and 2010 rank as the hottest years on record, while all 10 of the warmest years have occurred since 1998.
The news comes from an analysis by NASA's Goddard Institute for Space Studies (GISS), which monitors global surface temperatures. The average global temperature in 2012 was 14.6 degrees Celsius (58.3 degrees Fahrenheit), which is .6 degrees C (1.0 degrees F) warmer than the mid-20th century baseline average.
The researchers emphasized that, though weather patterns cause fluctuations in average temperature from one year to the next, long-term trends show a warming planet.
"One more year of numbers isn't in itself significant," said Gavin Schmidt, a GISS climatologist. "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."
Scientists have also shown that carbon dioxide levels in the Earth's atmosphere have been rising for decades. In 1880 the levels of carbon dioxide in the atmosphere was 285 parts per million. The levels now sit at over 390 parts per million.
While the worldwide temperature was only the ninth hottest on record, the continental U.S. had its warmest year on record during 2012.
"The U.S. temperatures in the summer of 2012 are an example of a new trend of outlying seasonal extremes that are warmer than the hottest seasonal temperatures of the mid-20th century," said James E. Hansen, GISS director. "The climate dice are now loaded. Some seasons still will be cooler than the long-term average, but the perceptive person should notice that the frequency of unusually warm extremes is increasing. It is the extremes that have the most impact on people and other life on the planet."
The visualization seen in the video below depicts the Earth's yearly temperatures when compared to the baseline averages from 1951 to 1980.
(Image courtesy NASA Goddard's Scientific Visualization Studio)