Earth’s global surface temperatures in 2017 ranked as the second warmest since 1880, according to an analysis by scientists at NASA’s Goddard Institute for Space Studies (GISS). Continuing the planet’s long-term warming trend, globally averaged temperatures in 2017 were 0.90 degrees Celsius (1.62 degrees Fahrenheit) warmer than the 1951 to 1980 mean. That is second only to global temperatures in 2016.
In a separate independent analysis, scientists at the National Oceanic and Atmospheric Administration (NOAA) concluded that 2017 was the third-warmest year in their record. The minor difference in rankings is due to slightly different methods used by the two agencies to analyze global temperatures. The long-term records of the two agencies remain in strong agreement, and both analyses show that the five warmest years on record have all taken place since 2010.
Because the locations and measurement practices of weather stations change over time, there are uncertainties in the interpretation of specific year-to-year global mean temperature differences. Taking this into account, NASA estimates that the 2017 global mean change is accurate to within 0.1 degree Fahrenheit, with a 95 percent certainty level.
”Despite colder than average weather in any one part of the world,” said GISS Director Gavin Schmidt, “temperatures over the planet as a whole continue the rapid warming trend we have seen over the last 40 years.”
Earth’s average surface temperature has risen a little more than 1 degree Celsius (about 2 degrees Fahrenheit) during the past century or so, a change driven largely by increased carbon dioxide and other human-made emissions into the atmosphere. 2017 was the third consecutive year in which global temperatures were more than 1 degree Celsius (1.8 degrees Fahrenheit) above late 19th-century levels.
Phenomena such as El Niño and La Niña—which warm and cool the tropical Pacific Ocean and cause corresponding variations in global wind and weather patterns—contribute to short-term variations in global temperatures. Also, weather dynamics affect regional temperatures, so not every region on Earth experienced similar amounts of warming last year. Warming trends are strongest in the Arctic regions.
The NASA GISS team assembles its analysis from publicly available data acquired by roughly 6,300 meteorological stations around the world; from ship- and buoy-based instruments measuring sea surface temperature; and from Antarctic research stations. This raw data is analyzed using methods that account for the distribution of temperature stations around the globe and for urban heating effects that could skew the calculations.