Last year was likely the warmest year since 1880, the National Oceanic and Atmospheric Administration confirmed on Thursday in a report written by hundreds of scientists from 58 countries.
The report analyzes four independent datasets of global temperature records, but its authors caution that their conclusion isn't definitive. "We cannot conclusively claim that 2014 was the warmest year in the real world when uncertainty is factored in," they wrote. But 2014 at least was the second-warmest and undoubtedly a record-setting year on a local level for many places on the globe. With very high statistical confidence, the authors reported that the 15 warmest years on record have all occurred since 1997.
NOAA and NASA, which record temperature observations independently, both had reported in January that 2014 was likely the warmest year on record.
Ocean surface temperatures, average sea level and atmospheric greenhouse gas concentrations were also at record high levels in 2014, according to the new "State of the Climate in 2014" report that incorporated data from across the globe.
"The variety of indicators shows us how our climate is changing, not just in temperature but from the depths of the oceans to the outer atmosphere,” Thomas R. Karl, director of NOAA's National Centers for Environmental Information, said in a news release.
The oceans in particular have seen dramatic changes as a result of heat trapped by greenhouses gases from human activity. Oceans absorb about 93 percent of the excess heat in the Earth's system, according to NOAA.
“The heat content is just continuing to pile up,” NOAA oceanographer Greg Johnson said during a press call on Thursday, reported Climate Central.
Deke Arndt, a report co-editor and chief of NOAA's climate monitor program, said the seas "were just ridiculous" last year.
Record ocean heat, at both the surface and in the depths, and record land temperatures are made worse by record-high levels of heat-trapping greenhouse gases, including carbon dioxide, methane and nitrous oxide. The global average CO2 level in 2014 was 397.2 parts per million. Carbon dioxide, which is responsible for about two-thirds of the energy changes caused by greenhouse gases, stood at 354.0 ppm when the first State of the Climate report was released in 1990, and today's levels are more than 40 percent higher than at the start of the Industrial Revolution.
In the lengthy report, the authors also note that the Arctic is warming and sea ice continues a long-term decline. Permafrost and glacial ice are declining, and snow cover in North America and Eurasia is also consistently below average and melting earlier in the year.
Thursday's annual State of the Climate report is the 25th such report, and the 20th to be published in the Bulletin of the American Meteorological Society. Read the full report here.
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