It's not rare for a year to break record temperatures. But it's now happened two years in a row — and 2015 was "very, very clearly the warmest year by a long chalk," says Gavin Schmidt, director of NASA's Goddard Institute for Space Studies.
NASA is presenting the annual review of global average temperatures in conjunction with NOAA, which says that not only did 2015 finish as the warmest year on record, but it did so by the widest margin ever — nearly a third of 1 degree Fahrenheit warmer than 2014's average.
In 2015, the average temperature on land and ocean surfaces around the world was "1.62° F (0.90° C) above the 20th century average," according to NOAA.
That makes 2015 the hottest since instrument records began being kept in 1880, beating the record set in 2014 by 0.29° F (0.16° C).