(Adds comment, background from NOAA expert, paragraphs 4-10) WASHINGTON, March 15 (Reuters) - This has been the world's warmest winter since record-keeping began more than a century ago, the U.S. government agency that tracks weather reported on Thursday. The National Oceanic and Atmospheric Administration (NOAA) said the combined global land and ocean surface temperature from December through February was at its highest since records began in 1880. A record-warm January was responsible for pushing up the combined winter temperature, according to the agency's Web site, http://www.noaa.gov. "Contributing factors were the long-term trend toward warmer temperatures as well as a moderate El Nino in the Pacific," Jay Lawrimore of NOAA's National Climatic Data Center said in a telephone interview from Asheville, North Carolina. The next-warmest winter on record was in 2004, and the third warmest winter was in 1998, Lawrimore said. The ten warmest years on record have occurred since 1995. "We don't say this winter is evidence of the influence of greenhouse gases," Lawrimore said. However, he noted that his center's work is part of the Intergovernmental Panel on Climate change process, which released a report on global warming last month that found climate change is occurring and that human activities quite likely play a role in the change. "So we know as a part of that, the conclusions have been reached and the warming trend is due in part to rises in greenhouse gas emissions," Lawrimore said. "By looking at long-term trends and long-term changes, we are able to better understand natural and anthropogenic (human-caused) climate change." The combined temperature for the December-February period was 1.3 degrees F (0.72 degree C) above the 20th century mean, the agency said. Lawrimore did not give an absolute temperature for the three-month period, and said the deviation from the mean was what was important. He did not provide the 20th century mean temperature. Temperatures were above average for these months in Europe, Asia, western Africa, southeastern Brazil and the northeast half of the United States, with cooler-than-average conditions in parts of Saudi Arabia and the central United States. Global temperature on land surface during the northern hemisphere winter was also the warmest on record, while the ocean-surface temperature tied for second warmest after the winter of 1997-98. Over the past century, global surface temperatures have increased by about 0.11 degree F (0.06 degree C) per decade, but the rate of increase has been three times larger since 1976 -- around 0.32 degree F (0.18 degree C) per decade, with some of the biggest temperature rises in the high latitudes of the Northern Hemisphere.
