The United States saw its second-hottest year on record in 2015, federal scientists announced on Thursday.
The annual average temperature in 2015 in the U.S. was 54.4 degrees Fahrenheit, or 2.4 degrees above the 20th century average, the National Oceanic and Atmospheric Administration (NOAA) announced Thursday.
The announcement came after a record-breaking December. Last month was 6 degrees above the 20th century average, NOAA said, smashing a record set in 1939.
The record heat in the U.S. comes as NOAA and its international counterparts are expected to name 2015 the hottest year on record around the world.
Though that announcement has yet to be made, it has long been expected that the year will top the charts internationally. In December, NOAA said the average surface temperature that month would need to be 1.46 degrees Celsius below average in order to avoid topping the charts.
Last year was also the third-wettest on record, NOAA said. December was both record hot and wet, the first time that has happened in a single month in 121 years of record keeping.
The year featured 10 severe weather disasters that caused at least $1 billion in damage. Those events covered five separate disaster types — wildfires, floods, winter storms, drought and severe weather — when most other years feature only three or four, officials said.
Thursday's report also comes as environmentalists and policy-makers renew their focus on climate change and begin aggressively pushing policies to keep the Earth from warming by more than 2 degrees Celsius this century, a figure scientists warn will bring about the worst of global warming.
International negotiators last month reached an agreement on a climate accord designed to cut warming-causing carbon emissions around the globe. President Obama has made climate change a major focus of his second term, and he’s promised to put the U.S. on the path of cutting emissions by 26 to 28 percent from 2005 levels by 2025.
NOAA scientists blamed the year’s records on a confluence of events, including the burgeoning El Nino in the Pacific Ocean, climate change and unique temperature patterns that developed throughout the year.
“I wouldn’t pin all of this on El Nino or overall large-scale global warming,” Deke Arndt, the chief of NOAA’s Climate Monitoring Branch, told reporters Thursday.
“Climate is an outcome of many ingredients and many factors working together to give us the outcome that they do, and they all came together to give us the year that we had.”
—This post was updated at 11:42 a.m.