Last year was Earth's warmest on record, bolstering the argument that people are altering the planet's climate by relentlessly burning fuels that belch greenhouse gases into the air, two major U.S. government agencies said on Friday.
Separate studies by the U.S. space agency NASA and the National Oceanic and Atmospheric Administration showed that the 10 warmest years on record have taken place since 1997.
The scientists said the record temperatures were spread around the globe, including most of Europe stretching into northern Africa, the western United States, far eastern Russia into western Alaska, parts of interior South America, parts of eastern and western coastal Australia and elsewhere.
"While the ranking of individual years can be affected by chaotic weather patterns, the long-term trends are attributable to drivers of climate change that right now are dominated by human emissions of greenhouse gases," said Gavin Schmidt, director of NASA's Goddard Institute of Space Studies in New York.
He told reporters, "the data shows quite clearly that it's the greenhouse gas trends that are responsible for the majority of the trends." The trends in greenhouse gas emissions are continuing, "so we may anticipate further record highs in the years to come," Schmidt added.
Scientists have warned of grave consequences this century if global temperatures keep rising as anticipated, including heavily populated coastal regions being swamped by rising ocean levels, more deadly extreme weather events, droughts that may harm food production and others.
This year representatives of about 200 governments will meet in Paris to try to forge a deal to limit global warming to avoid floods, droughts, heatwaves and rising sea levels blamed on increasing emissions of greenhouse gases, which result from burning of fossil fuels such as coal and oil.
Five times higher
The scientists said computer models show that the change in global temperatures is five times higher than it would be if natural phenomena such as volcanic eruptions and solar heating were acting alone. Including contributions from human activity, such as greenhouse gas emissions, "we get a good match to those long-term trends," Schmidt said.
"Taken together, the warm temperatures of the recent decades demonstrate the impact of greenhouse gases on our climate, and invalidate the sound bite that global warming has somehow 'stopped,'" said Joe Casola, a staff scientist at the Center for Climate and Energy Solutions.
The scientists said the global average temperature over land and ocean surfaces for 2014 was the highest since record keeping began in 1880.
Since 1880, Earth's average surface temperature has warmed by about 1.4 degrees Fahrenheit (0.8 degrees Celsius), a trend that is largely driven by the increase in carbon dioxide and other human emissions into the planet's atmosphere, NASA said.
The NASA and NOAA analyses showed that the world's oceans all warmed last year, offsetting somewhat more moderate temperatures over land.
The average temperature across global land and ocean surfaces was 1.24 degrees F (0.69 degrees C) above the 20th century average, NOAA said. Last year's warmth surpasses the previous records of 2005 and 2010 by 0.07 degree F (0.04 degree C), the scientists said.
The scientists noted that the record was set in a year that did not have the weather pattern known as El Niסo that can heat up the atmosphere.
The findings buttress analysis by the United Kingdom and Japan of a warming planet.
"Multiple data sets from across the globe continue to validate each other and validate the long-term trends that we are seeing," said NOAA chief scientist Richard Spinrad.
Marshall Shepherd, a University of Georgia meteorologist, said, "If you are younger than 29 years old, you haven't lived in a month that was cooler than the 20th century average."
The United Nations says it is already clear that promises for emissions curbs at a Paris summit in December 2015 will be too weak to get on track for a UN goal of limiting global warming to 3.6 degrees F (2 degrees C) above pre-industrial times.
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