A child uses a wide brimmed hat and an ice cream to keep cool in Shenyang, Liaoning province, July 7, 2015. [Photo/CFP]

WASHINGTON - Blistering heat blanketed the Earth in 2015 like never before, making it by far the hottest year by the widest margin on record, and reflecting a continued long-term warming trend in global climate change.

Last year was the planet's warmest since modern record keeping began in 1880, boosted by a long-term build-up of greenhouse gases and a

strong El Nino warming the Pacific Ocean, two major U.S. government agencies said Wednesday.

"Climate change is the challenge of our generation," Charles Bolden, head of the U.S. space agency NASA, said in a statement. "It is a key data point that should make policy makers stand up and take notice -- now is the time to act on climate."

LARGEST MARGIN

A report by NASA showed that globally-averaged temperatures in 2015 shattered the previous mark set in 2014 by 0.13 degrees Celsius, noting that only once before, in 1998, has the new record been greater than the old record by this much.

The U.S. National Oceanic and Atmospheric Administration (NOAA), which used much of the same raw temperature data, but different analyzing methods, put 2015's average temperature at 14.80 degrees Celsius, which was 0.90 degrees Celsius above the 20th century average.

"This was the highest among all 136 years in the 1880-2015 record, surpassing the previous record set last year by 0.16 degrees Celsius and marking the fourth time a global temperature record has been set this century," the NOAA report wrote.

"This is also the largest margin by which the annual global temperature record has been broken," it said.

NO SURPRISE

The announcements didn't come as a surprise, with 10 out of the 12 months last year being the warmest for their respective months on record. Only January was the second warmest January on record and April third warmest.

"You can see that we broke the record each month for the warmest month on record, except for two months," Thomas Karl, director of NOAA's National Centers for Environmental Information, told reporters during a media teleconference. "That's the first time we've seen that."

Besides, the five highest monthly departures from average for any month on record all occurred last year.

Overall, record warmth was seen around the world in 2015, including Central America, the northern half of South America, parts of northern, southern, and eastern Europe stretching into western Asia, a large section of east central Siberia and regions of eastern and southern Africa.