"The 12 hottest years on record have all come in the last 15."
President Barack Obama, in his State of the Union address
In 2012, the country experienced severe weather threats including drought, a devastating Hurricane Sandy and severe thunderstorms. We decided to fact-check whether the 12 hottest years on record have all come since 1998.
The White House directed us to NASA's Goddard Institute for Space Studies, which tracks global surface temperatures. The institute concluded that 2012 was the ninth-warmest year on record, with 2010 and 2005 being the all-time highs.
For the contiguous United States, 2012 was the country's warmest year yet. It beat the previous record by one degree Fahrenheit.
Reto Ruedy, a program manager at the Goddard Institute, told PolitiFact that the institute's data produce the following ranking of hottest years. Items on the same line are statistically tied.
1-2: 2010, 2005
3-8: 2007, 1998, 2002, 2003, 2006, 2009
9-12: 2012, 2011, 2001, 2004
This analysis shows that 13 of the warmest years have occurred in the past 15 years. Alternately, one could say that 12 of the warmest years came in the last 13.
We see a few other issues to note.
• The NASA data set isn't the only one available. The National Oceanic and Atmospheric Administration also analyzes global surface temperatures using its own methodology. The two measurements diverge somewhat — NOAA considers 2012 the 10th-warmest year on record since records began in 1880, rather than the ninth. However, NOAA's data for land and ocean temperature anomalies show that 14 of the past 15 years were the hottest on record.
• There are other ways one could measure "hottest years." Kevin Trenberth, a scientist with the National Center for Atmospheric Research, agreed with the 13-of-15 calculation. But he added that the NASA and NOAA values refer to global mean surface temperature. "One could define 'hottest' in other ways, such as by how much Arctic sea ice there is," he said.
Obama said, "The 12 hottest years on record have all come in the last 15." Obama was actually over-cautious in his statement, so we rate his statement True.
This report has been edited for print. Read the full version at PolitiFact.com.