Globally, average temperatures in 2015 shattered the previous mark set in 2014 by 0.23 degrees F. (0.13 C.). Only once before, in 1998, has the new record been greater than the old record by this much, reports NASA and the National Oceanic and Atmospheric Administration (NOAA).
The 2015 temperatures continue a long-term warming trend.
Earth’s average surface temperature has risen about 1.8 degrees F since the late 19th century, says NASA. Most of the warming occurred in the past 35 years, with 15 of the 16 warmest years on record occurring since 2001.
NASA’s analyses incorporate surface temperature measurements from 6,300 weather stations, ship- and buoy-based observations of sea surface temperatures and temperature measurements from Antarctic research stations. NASA monitors Earth’s vital signs from land, air and space with a fleet of satellites, as well as airborne and ground-based observation campaigns.
The record-warm 2015 coincided with the largest-ever recorded annual growth of atmospheric carbon dioxide (CO2) at the Mauna Loa Observatory in Hawaii. The annual increase of 3 parts per million (ppm) was larger than 2 ppm for each of the last four years, another first, reported NOAA.
Climate researchers blamed the rise in atmospheric CO2 primarily on the rate of emissions from the burning of coal, oil and natural gas.
“Carbon dioxide levels are increasing faster than they have in hundreds of thousands of years,” says Pieter Tans, leader of NOAA’s Global Greenhouse Gas Reference Network. “It’s explosive compared to natural processes.”