This winter in the northern hemisphere was the warmest on record, the US government said in the latest report focusing on changing climate.
The Washington report comes just over a month after the Intergovernmental Panel on Climate Change said global warming was very likely caused by human actions and is so severe it will continue for centuries.
The National Oceanic and Atmospheric Administration said the combined land and ocean temperatures from December to February were 1.3 degrees Fahrenheit above average for the period since record keeping began in 1880.
During the past century, global temperatures had increased at about 0.11 degrees Fahrenheit per decade. But that increase has been three times larger since 1976, NOAA's National Climatic Data Centre reported.
Most scientists attribute the rising temperatures to so-called greenhouse gases which are produced by industrial activities, transport emissions and other processes. These gases build up in the atmosphere and trap heat from the sun somewhat like a greenhouse.
Also contributing to this winter's record warmth was an El Nino, a periodic warming of the tropical Pacific Ocean. It was particularly strong in January - the warmest January ever - but the ocean surface had since begun to cool.
The report noted that in the Northern Hemisphere the combined land and water temperature was the warmest ever at 1.64 degrees Fahrenheit above average. In the Southern Hemisphere, where it was summer, the temperature was 0.88 Fahrenheit above average and the fourth warmest.
The late March date of the vernal equinox noted on most calendars notwithstanding, for weather and climate purposes northern winter is December, January and February.
For the United States, meanwhile, the winter temperature was near average.
The season got off to a late start and spring-like temperatures covered most of the eastern half of the country in January, but cold conditions set in in February, which was the third coldest on record.
AP