Last year shattered 2014’s record to become the hottest year since reliable record-keeping began, two government science agencies announced Wednesday.

2015’s sharp spike in temperatures was aided by a strong El Niño weather pattern late in the year that caused ocean waters in the central Pacific to heat up. But the unusual warming started early and steadily gained strength in a year in which 10 of 12 months set records, scientists said.

The new figures, based on separate sets of records kept by NASA and the National Oceanic and Atmospheric Administration, could fuel debate over climate change in an election year in which the two main political parties remain divided over what to do about global warming and, indeed, whether it exists.

“2015 was by far the record year in all of the temperature data sets that are based on the instrumental and surface data,” said Gavin Schmidt, director of the Goddard Institute for Space Studies at NASA, which made the announcement jointly with NOAA.

“It really underlines the fact that the planet really is still warming, there is no change in the long-term global warming rate, and we know why that is,” he said.

NASA reported that 2015 was officially 0.23 degrees Fahrenheit (0.13 degrees Celsius) hotter than 2014, the previous record year, a sharp increase for a global temperature record in which annual variation is normally measured in hundredths of a degree. NOAA’s figures showed slightly greater warming, of about 0.29 degrees Fahrenheit (0.16 degrees Celsius).

“This record, we literally smashed,” said Thomas Karl, director of NOAA’s National Centers for Environmental Information. “It was over a quarter of a degree Fahrenheit, and that’s a lot for the global temperature.”

The record can’t be entirely attributed to the warming of the globe by human greenhouse-gas emissions. The year’s powerful El Niño unlocked immense heat from the Pacific Ocean that drove up the global temperature.

But at the same time, 2015 was also considerably hotter than 1998, another major El Niño year that was, at the time, the hottest year on record. Now, in contrast, it’s fifth or sixth on the list.

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