The continental United States experienced the warmest spring on record this year, with temperatures far above the average over the past century, government scientists said Thursday.

The United States, excluding Alaska, Hawaii and overseas territories, had an average temperature of 57.1 degrees Fahrenheit (13.9 Celsius) from March through May, 5.2 degrees (2.9 Celsius) above the average from 1901 to 2000, the data showed.

"Spring 2012 marked the largest temperature departure from average of any season on record for the contiguous United States," the National Oceanic and Atmospheric Administration said in a statement.

This year's spring was up 2.0 degrees (1.1 Celsius) from the previous warmest spring in the United States which was recorded in 1910, the agency said.

The year from June 2011 through May also marked the warmest 12-month period on record after a hot summer and warmer winter. The average temperature was 3.2 degrees (1.8 Celsius) above average, the agency said.

In terms of monthly figures, the United States experienced the warmest March, the third warmest April and the second warmest May, the agency said.

Scientists have repeatedly warned that emissions of greenhouse gases, largely through industrial activity, are heating up the planet and could spell serious long-term problems, including the extinction of plant and animal species and the flooding of low-lying islands.

UN-led efforts for a new global climate agreement have moved slowly. Climate change remains a controversial topic in the United States, with many prominent members of the Republican Party casting doubt on the science.

Proposals backed by President Barack Obama and his Democratic allies to mandate cuts in emissions have died in Congress. Critics say the measures would be too costly to a fragile economy.

US emissions of greenhouse gases rose in 2010 after a brief downward turn, according to official data.

China has surpassed the United States as the largest emitter. The Asian power has pledged to reduce the intensity of its emissions per unit of economic growth, but not in absolute terms.