"It's hard to read the report and not be led to the conclusion that the task of reducing carbon emissions is now more urgent than ever," said Michael Mann, a leading US climatologist at Pennsylvania State University who was not involved in the research.
Globally, according to four independent analyses cited by the study "2012 ranked as the eighth or ninth warmest year since records began in the mid-to-late 1800s.
"The year was 0.14°C-0.17°C above the 1981-2010 average, depending on the dataset considered," said the report published in the Bulletin of the American Meteorological Society.
When it comes to Arctic sea ice, a new record low was observed in September and another all-time low for snow cover was recorded in the Northern Hemisphere, it said.
"Surface temperatures in the Arctic are increasing at a rate about two times faster than the rest of the world," said Jackie Richter-Menge, research civil engineer with the US Army Corps of Engineers.
"In the Arctic, the records or near records being reported from year to year are no longer anomalies or exceptions," she added.