The annual State of the Climate report 2013 is a review of scientific data and weather events over the past year, compiled by 425 scientists from 57 countries.
"These findings reinforce what scientists for decades have observed: that our planet is becoming a warmer place," said National Oceanic and Atmospheric Administration administrator Kathryn Sullivan.
Global temperatures were among the warmest on record worldwide, with four major datasets showing 2013 ranked between second and sixth for all-time heat.
"Australia observed its warmest year on record, while Argentina had its second warmest and New Zealand its third warmest," said the report.
Sea surface temperatures also rose, making last year among the 10 warmest on record.
The Arctic marked its seventh warmest year since records began in the early 1900s.
Arctic sea ice cover was the sixth lowest since satellite observations began in 1979.
On average, global sea levels also rose, keeping pace with a trend of adding about three millimeters per year over the past two decades, it said.
Methane, carbon dioxide and other greenhouse gases that come from burning fossils fuels "continued to rise during 2013, once again reaching historic high values," said the report.
For the first time, the daily concentration of C02 in the atmosphere exceeded 400 parts per million (ppm), as measured by the Mauna Loa Observatory in Hawaii, a year after observational sites in the Arctic observed C02 at 400 ppm in spring 2012.
The report, published in the peer-reviewed Bulletin of the American Meterological Society, offers a "detailed scientific snapshot of what's happening in our world," said the group's executive director Keith Seifer.