NOAA, NASA: 2015 was Earth's hottest by a wide margin

WASHINGTON - Last year wasn't just the Earth's hottest year on record - it left a century of high temperature marks in the dust.

The National Oceanic Atmospheric Administration and NASA announced Wednesday that 2015 was by far the hottest year in 136 years of record keeping. For the most part, scientists at the agencies and elsewhere blamed man-made global warming, with a boost from El Niño.

NOAA said 2015's temperature was 58.62 degrees Fahrenheit (14.79 degrees C), passing 2014 by a record margin of 0.29 degrees. That's 1.62 degrees above the 20th-century average. NASA, which measures differently, said 2015 was 0.23 degrees warmer than the record set in 2014 and 1.6 degrees above 20th century average.

Because of the wide margin over 2014, NASA calculated that 2015 was a record with 94 percent certainty, more than double the certainty it had last year when announcing 2014 as a record. NOAA put the number at above 99 percent - or "virtually certain," said Tom Karl, director of NOAA's National Centers for Environmental Information.

For the first time Earth is 1 degree Celsius (1.8 degrees F) warmer than it was in preindustrial times, NOAA and NASA said. That's a key milestone because world leaders have set a threshold of trying to avoid warming of 1.5 or degrees Celsius above preindustrial times.

Because of the pace of rising temperatures, "we don't have very far to go to reach 1.5," Karl said.

But 1.5 or 2 degrees are not "magic numbers" and "we're already seeing the impacts of global warming," said NASA Goddard Institute of Space Studies director Gavin Schmidt.

"This trend will continue; it will continue because we understand why it's happening," Schmidt said. "It's happening because the dominant force is carbon dioxide" from the burning of fossil fuels.

Although 2015 is now the hottest on record, it was the fourth time in 11 years that Earth broke annual marks for high temperature.

"It's getting to the point where breaking record is the norm," Texas Tech climate scientist Katharine Hayhoe said. "It's almost unusual when we're not breaking a record."

December 2015 was the 10th month last year that set a monthly warmth record, with only January and April not hitting high marks.

"That's the first time we've seen that," said NOAA's Karl.

In December, the globe was 2 degrees Fahrenheit warmer than normal, beating the old record set in 2014 by more than a half a degree, NOAA calculated.