NASA, NOAA data show 2016 warmest year on record globally
Globally-averaged temperatures in 2016 were 1.78 degrees Fahrenheit (0.99 degrees Celsius) warmer than the mid-20th century mean. This makes 2016 the third year in a row to set a new record for global average surface temperatures.
The 2016 temperatures continue a long-term warming trend, according to analyses by scientists at NASA's Goddard Institute for Space Studies (GISS) in New York.
NOAA scientists concur with the finding that 2016 was the warmest year on record based on separate, independent analyses of the data.
Because weather station locations and measurement practices change over time, there are uncertainties in the interpretation of specific year-to-year global mean temperature differences.
However, even taking this into account, NASA estimates 2016 was the warmest year with greater than 95 percent certainty.
The planet's average surface temperature has risen about 2.0 degrees Fahrenheit (1.1 degrees Celsius) since the late 19th century, a change driven largely by increased carbon dioxide and other human-made emissions into the atmosphere.
Most of the warming occurred in the past 35 years, with 16 of the 17 warmest years on record occurring since 2001.
Not only was 2016 the warmest year on record, but eight of the 12 months that make up the year – from January through September, with the exception of June – were the warmest on record for those respective months.
October, November, and December of 2016 were the second warmest of those months on record – in all three cases, behind records set in 2015.
Phenomena such as El Niño or La Niña, which warm or cool the upper tropical Pacific Ocean and cause corresponding variations in global wind and weather patterns, contribute to short-term variations in global average temperature.
A warming El Niño event was in effect for most of 2015 and the first third of 2016. Researchers estimate the direct impact of the natural El Niño warming in the tropical Pacific increased the annual global temperature anomaly for 2016 by 0.2 degrees Fahrenheit (0.12 degrees Celsius).
Weather dynamics often affect regional temperatures, so not every region on Earth experienced record average temperatures last year. For example, both NASA and NOAA found the 2016 annual mean temperature for the contiguous 48 United States was the second warmest on record.
In contrast, the Arctic experienced its warmest year ever, consistent with record low sea ice found in that region for most of the year.
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.
These raw measurements are analyzed using an algorithm that considers the varied spacing of temperature stations around the globe and urban heating effects that could skew the conclusions.
The result of these calculations is an estimate of the global average temperature difference from a baseline period of 1951 to 1980.
NOAA scientists used much of the same raw temperature data, but with a different baseline period, and different methods to analyze Earth's polar regions and global temperatures.
GISS is a laboratory within the Earth Sciences Division of NASA's Goddard Space Flight Center in Greenbelt, Maryland.
The laboratory is affiliated with Columbia University's Earth Institute and School of Engineering and Applied Science in New York. ■