2014 was Earth's warmest year on record, scientists say
Earth's average surface temperature was the warmest since record-keeping began in 1880, according to NASA and the National Oceanic and Atmospheric Administration.
December also was the warmest month ever recorded, and was among five months that set records, the agencies reported Friday.
The combined land and ocean surface temperature was 1.24 degrees above the 20th century average of 57 degrees, according to NOAA. December's average global temperature was 1.39 degrees above that 20th century average. The four other months that set records were May, June, August and September, NOAA said. October tied for warmest, according to the agency's report.
The data add to a two-decade string of record warmth planetwide. Except for 1998, the 10 warmest years on record have occurred since 2002, according to NOAA.
The increase in global average surface temperatures was driven in part by an all-time record year for ocean temperatures, and it came despite a decidedly colder winter driven by a "polar vortex" in much of the U.S., according to the agencies. That cold anomaly was overwhelmed by many other hot anomalies planetwide, agency officials said.
"This was very clearly the record warmest year in the ocean records," said Gavin Schmidt, director of NASA's Goddard Institute for Space Studies in New York. "It wasn’t quite the warmest year in the land records, but combined, this did actually give the warmest year” for the planet surface.
Notable areas of unusual warmth included Alaska, the Pacific Coast of the U.S., Europe, Siberia and Australia, he said.
The scientists said the rising trend can be attributed to the warming effect of human activity, including the burning of fossil fuels that add greenhouse gases to the atmosphere.
“Greenhouse gas trends are responsible for the majority of the trend that we see,” Schmidt said. Because such emissions continue to rise, he added, “we may anticipate further record highs in the years to come.”
Last year's high bested three years that were influenced by the ocean circulation phenomenon known as El Niño, which usually pushes land temperatures upward, according to the agencies. Last year was not considered an El Niño, year, although the Japanese Meteorological Agency has said December appeared to be the beginning of a mild El Niño. U.S. agencies have not agreed.
“It’s unlikely we’ll have anything more than a weak El Niño as the year progresses,” said Tom Karl, head of NASA's National Climatic Data Center in North Carolina.
Snow cover in northern latitudes during season transitions was of particular concern, Karl said.
“We see significant decreases in spring and early summer months," he said. "It’s important because that’s when the sun is high. A lot of additional heat is gained because there’s less snow to reflect the sunlight back to space.”
Sea ice levels were at record lows in the Arctic, but remained high in the Antarctic, Schmidt noted.
“This last year was about the sixth lowest annual anomaly for Arctic sea ice,” said Schmidt. “In the Antarctic, 2014 was actually the highest Antarctic sea ice extent, which is a little surprising given the warmth on the rest of the planet.”
Antarctic sea ice extent is not as closely linked to surface temperature trends, and is influenced by many local factors, including winds linked to the hole in the ozone layer and additional fresh water from melting land ice sheets, Schmidt said.
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Copyright © 2015, Los Angeles TimesUPDATES
10:37 a.m.: This article has been updated with information about El Niño and snow and ice levels.
9:50 a.m.: This article has been updated with additional comments from Gavin Schmidt of NASA.
9:25 a.m.: This article has been updated with additional comments and details.
8:34 a.m: This article has been updated with background information on ocean temperatures.
This article was originally published at 8:14 a.m.
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