It wasn't even close.
In all of recorded history back to the mid-19th century, we haven’t seen a year warmer than 2015. Everywhere scientists looked, from Siberia to northern South America, to all of the world's major ocean basins, they found record to near-record warmth.
This was the announcement the National Oceanic and Atmospheric Administration (NOAA) and NASA jointly made on Wednesday, using their databases of global surface temperatures dating back to 1880. The warmest year news was also echoed by independent findings from the UK’s Hadley Center, which keeps its own global temperature records.
According to NASA, globally averaged surface temperatures in 2015 shattered the previous mark set in 2014 by 0.13 degrees Celsius, or 0.23 degrees Fahrenheit. "Only once before, in 1998, has the new record been greater than the old record by this much," NASA said in a press release.
Taking uncertainties regarding surface temperature data into account, NASA noted that its scientists have 94 percent certainty that 2015 was the warmest year.
“It was much much warmer than 2014, and 2014 itself was a record,” said Gavin Schmidt, the director of NASA’s Goddard Institute for Space Studies, in an interview with Mashable.