Global surface temperatures last year were tied with 2003 as the fourth-warmest on record, the National Oceanic and Atmospheric Administration reported Tuesday.
Nine of the 10 warmest years since records began in 1880 have occurred this century, according to NOAA.
The latest annual data arrives as the Obama administration is crafting new rules to curb carbon emissions from power plants and liberal Senate Democrats are trying to play political offense on climate change.
According to NOAA's data, 2010 was the warmest year on record globally, followed by 2005 and 1998.
NASA, which provides rankings based on slightly different calculations, said Tuesday that 2013 was tied with 2009 and 2006 as the seventh-warmest on record (check out these slides for more on that).
The trend, a top NASA scientist said, is unmistakable.
"Long-term trends in surface temperatures are unusual and 2013 adds to the evidence for ongoing climate change," said climatologist Gavin Schmidt of NASA's Goddard Institute for Space Studies.
Global-warming skeptics have seized on the relative lack of surface warming since 1998 when battling federal regulations, and challenging the overwhelming majority of scientists who say human-induced climate change is a reality.
But NASA, echoing a 2013 report by the World Meteorological Organization, noted the decade-over-decade averages continue to show warming.
"Each successive year will not necessarily be warmer than the year before, but with the current level of greenhouse gas emissions, scientists expect each successive decade to be warmer than the previous," NASA said in a statement alongside its latest data.