Last year was Earth's hottest on record in a new sign that people are disrupting the climate by burning fossil fuels that release greenhouse gases to the air, two U.S. government agencies said on Friday.
The White House said the studies, by the U.S. space agency NASA and the National Oceanic and Atmospheric Administration (NOAA), showed a need for action to reduce rising world emissions of greenhouse gases.
The data showed that the 10 warmest years since records began in the 19th century had occurred since 1997. Last year was warmest, ahead of 2010, 2005 and 1998. The records undercut arguments by climate skeptics that global warming has stopped in recent years.
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.
'The data shows quite clearly that it's the greenhouse gas trends that are responsible for the majority of the trends,' he told reporters. Emissions were still rising 'so we may anticipate further record highs in the years to come.'
U.N. studies show there already are more extremes of heat and rainfall and project more disruptions to food and water supplies and rising sea levels as ice melts from Greenland to Antarctica.
In December, about 200 governments will meet in Paris to try to reach a deal to limit global warming, shifting to renewable energies. China and the United States, the top emitters of greenhouse gases, say they are cooperating more to achieve an U.N. accord.
'We can't wait to take action,' a White House official said in a statement.
Opponents of the proposed Keystone XL pipeline that would take Canadian crude across the United States said the new data made it all the more pressing to prevent the construction of the pipeline.
But U.S. Senator James Inhofe, the Senate's leading climate change skeptic, said the difference between 2014 and 2010 was so insignificant as to prove there was no need for more stringent EPA regulations.
'Human activity is clearly not the driving cause for global warming, and is not leading our planet to the brink of devastation that many alarmists want us to believe,' he said.
In Britain, Energy and Climate Change Secretary Ed Davey said the records were 'yet more evidence that we need to act urgently to prevent dangerous climate change.'
The U.N.'s Intergovernmental Panel on Climate Change (IPCC) says it is at least 95 percent probable that human activities, rather than natural variations in the climate caused by factors such as sunspots, are to blame for rising temperatures.
Rowan Sutton, director of Climate Research at the National Centre for Atmospheric Science at the University of Reading, said a single year did not mean much because it might be a freak hot year.
'But the fact that now 14 of the 15 warmest years on record have occurred since the turn of the century shows just how clear global warming has become,' he said.
Even so, temperatures since 1998, a warm year, have not risen as fast as they did in the 1980s or 1990s. The IPCC has described it as a hiatus in warming.
Since 1880, Earth's average surface temperature has warmed by about 1.4 degrees Fahrenheit (0.8 degrees Celsius), 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 Niño that can heat up the atmosphere and has been a factor in many past record-setting years.
The United Nations says it is already clear that promises for emissions curbs at the Paris summit will be too weak to get on track for a U.N. goal of limiting global warming to 3.6 degrees F (2 degrees C) above pre-industrial times.