It's Official: 2015 Is the Hottest Year on Record

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In the end, it wasn't even close.

US science agencies confirmed Wednesday that 2015 not only set a second straight record for global average temperatures, it brought the Earth halfway to the point at which scientists warn climate change could become catastrophic.

Worldwide land and sea temperatures for the year averaged 0.9 degrees Celsius (1.62 Fahrenheit) over the 20th-century average, the National Oceanic and Atmospheric Administration reported. NASA figures showed temperatures ran 0.87 C (1.57 F) over the average for the 1951-1980 period. And while the mercury was boosted by the Pacific Ocean warming trend known as El Niño, 2015 would have been the warmest year on record even without it, said Gavin Schmidt, director of NASA's Goddard Institute for Space Studies.

"The reason why this is such a warm record year is because of the long-term underlying trend," Schmidt told reporters. "There is no evidence that that long-term underlying trend has slowed, paused, or hiatused at any point in the last few decades."

Not only did 2015 beat 2014's previous record, it did so in Secretariat-at-the-Belmont style, opening up an insurmountable lead as it neared the finish line. NOAA's figure ended up being .16 C higher than in 2014 — a huge gap in a field where readings normally bounce by a few hundredths of a degree.

"It's not just a record, it's a huge record," said Katharine Hayhoe, an atmospheric scientist at Texas Tech University in Lubbock. "This is like somebody winning the 100-meter dash at the Olympics by 10 meters."

2015 avg global temperature record warm at 1.62°F (0.90°C) above avg: https://t.co/ZVoiHfpHUr #StateOfClimate pic.twitter.com/h3jCaXCg9I

— NOAA NCEI Climate (@NOAANCEIclimate) January 20, 2016

Scientists had said a new record was all but certain by year's end, after several monthly marks set new records.

"It's not just one or two months that were so above the average that it drove the whole year," said Scott Weaver, senior climate scientist at the nonprofit Environmental Defense Fund. "It was really persistent, globally, throughout the year." And while a new high was expected, "The margin was definitely surprising."

Britain's Met Office released similar figures Wednesday morning, while Japan's meteorological agency reached a similar conclusion in December.

Of the 10 warmest years in a record that dates back to 1880, nine have occurred since 2000. In addition, 2015 is the first year that average temperatures were over 1 degree C warmer than the averages for the end of the 19th century, when regular temperature records started being kept, said Thomas Karl, director of NOAA's National Centers for Environmental Information.

That's halfway to the point where more than 190 countries agreed to try to halt warming by 2100, as part of the December agreement reached in Paris. Scientists warn that beyond 2 degrees, warming could have catastrophic consequences. World leaders also agreed to shoot for 1.5 degrees instead of 2, in hopes of minimizing the risks of disaster — but Karl said that figure is approaching fast.

"If we were to have a number of years comparable to this year, we don't have very far to go to reach one and a half," he said.

The Paris talks were aimed at getting United Nations members to cut back their emissions of carbon dioxide and other heat-trapping gases that have been driving the increased temperatures. The record heat and other freakish weather in 2015 definitely gave negotiators a push, said Hayhoe, who attended the conference.

The eastern United States and Canada saw a warm, wet Christmas, with tornadoes pounding the southern US states around the holiday. December temperatures in New York never dropped below freezing, while the unusually warm Atlantic fueled storms that smashed ashore and caused heavy flooding in the United Kingdom. Heat waves and droughts struck in the Middle East and Southeast Asia, where they worsened fires set to clear Indonesian rain forests for paper and palm plantations and shrouded the country in a choking haze. When fall came, the delayed monsoon rains led to flooding that killed hundreds of people in southern India.

"We have seen tropical storms that have ratcheted up overnight from a tropical storm to a Category 5," she said. "When I was coming back from Paris through the UK, the front-page news there was the fact that daffodils and tulips were now Christmas flowers—instead of coming up in March, they were blooming in December. And I come back to Toronto, where I'm from … and there were daffodils coming up in Canada on Christmas Day."

Weaver said the news was a sign that the Paris pact "needs to come out of discussion phase and really into the implementation phase."

"It's not surprising to us given the continued reliance on fossil fuel combustion and the fact that we're releasing more methane than we ever thought," he said.

Related: Republicans Threaten to Shred Historic UN Climate Agreement

Climate is an intensely political issue in the United States, where a presidential election is coming in November. The leading Democratic candidates both endorsed the findings Wednesday.

"Climate change is real. It's hurting our planet and our people. We can't afford a president who ignores the science," former Secretary of State Hillary Clinton's campaign tweeted. Vermont Sen. Bernie Sanders added, "This planet is in trouble."

There was no immediate response from the leading Republican candidates, though current front-runner Donald Trump has called global warming "bullshit" and Sen. Ted Cruz has used his Senate Commerce subcommittee to attack climate science.

Cruz and other opponents of cutting back on carbon emissions point to satellite temperature data that shows readings in the atmosphere, rather than on the surface, didn't set records in 2014 or 2015. Satellite data readings from the mid-troposphere—the layer of air from two to six miles above the surface—recorded only the third-highest readings since those records started being kept in 1979, NASA and NOAA reported.

But Hayhoe said satellite readings don't measure temperatures directly and have more uncertainty associated with them than thermometers on the ground or the ocean surface. And people don't live in the atmosphere; they live on the ground. At this point, the odds that temperatures are rising entirely due to natural causes are "vanishingly small."

"If it were happening due to random chance, you would have to somehow explain how we've wrapped an extra blanket around the planet and it isn't trapping heat," she said.

Follow Matt Smith on Twitter: @mattsmithatl

Image via Flickr