Last year was among the top 10 warmest for the globe on record, while polar sea ice coverage reached record lows in the Arctic and record highs in the Antarctic, according to an annual "State of the Climate" report published Tuesday.
Depending on what data set 2012 temperatures are compared to, global temperatures ranked 8th or 9th, according to the National Climatic Data Center. It was the warmest year on record for the United States and for Argentina.
The report also showed that the Arctic is warming at a rate twice as fast as in lower latitudes, with minimum Arctic sea ice extent at 1.32 million square miles in September and Northern Hemisphere snow cover extent in June both reaching new record lows.
In Antarctica, meanwhile, ice coverage reached a record maximum of 7.51 million square miles.
Sea surface temperatures were among the 11th warmest on record, the first significant rise since the turn of the 21st century.
Average sea level reached a record high, both because of increasing volume from melting ice and from expansion due to warmer water temperatures. Sea level rise is estimated to be rising at a rate of about 3 millimeters each year.
Scientists pointed to the various data points as evidence of changing climate.
"Many of the events that made 2012 such an interesting year are part of the long-term trends we see in a changing and varying climate-carbon levels are climbing, sea levels are rising, Arctic sea ice is melting, and our planet as a whole is becoming a warmer place," NOAA Administrator Kathryn D. Sullivan said on a conference call.
But the scientists stopped short of exploring the cause of the changes.
"This report is focused on what are the observations telling us, and, is it telling us a story that we think makes sense in a holistic picture of a changing planet?" said Thomas Karl, director of the climatic data center.
The report was published online Tuesday in the Bulletin of the American Meteorological Society.