2017 marks Earth's hottest year on record without El Niño, NASA reports

Earth’s global surface temperatures in 2017 ranked as the second warmest since global estimates became possible in 1880, according to a NASA analysis.

It is second only to global temperatures in 2016, where temperatures were bolstered by El Niño, which is considered the warm phase of El Niño Southern Oscillation. El Niño can cause warming effects around the globe due to the warmer water in the tropical Pacific Ocean.

Thus, 2017 was the warmest year without an El Niño event.

The year continued a decades-long warming trend around the globe, and 17 of the 18 warmest years have now occurred since 2001.

Globally averaged temperatures in 2017 were 1.62 degrees Fahrenheit higher than the 1951 to 1980 mean, according to scientists at NASA’s Goddard Institute for Space Studies (GISS).

While the Earth warmed overall, weather dynamics affect regional weather patterns. Therefore, different locations experience different amounts of warming.

“Despite colder than average temperatures in any one part of the world, temperatures over the planet as a whole continue the rapid warming trend we’ve seen over the last 40 years,” GISS Director Gavin Schmidt said to NASA.

Warming trends are strongest in the Arctic regions, which continued to experience a loss of sea ice in 2017.

Scientists from the National Oceanic and Atmospheric Administration (NOAA) produced a separate, independent analysis that shows strong agreement with NASA's report. However, the report concluded that 2017 was the third warmest year in their record.

The two agencies use different methods to analyze global temperatures, which contributed to the minor difference in rankings. Both reports found that the five warmest years on record have all taken place since 2010.

"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," the NASA report reads.

NASA scientists track global temperatures using measurements from 6,300 weather stations, Antarctic research stations, and ship- and buoy-based observations of sea-surface temperatures.

These raw measurements are analyzed using an algorithm that considers interference that could skew the conclusions. These calculations produce the global average temperature deviations from the baseline period of 1951 to 1980, according to NASA.

There are uncertainties in the interpretation of specific year-to-year global mean temperature differences due to changing weather station locations and measurement practices over time. Therefore, NASA estimates that 2017’s global mean change is accurate within 0.1 F, with a 95 percent certainty level.

The 2017 temperature data set and the complete methodology used to make the temperature calculations is provided by NASA.

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