The world in 2017 saw some of the hottest surface temperatures even without El Nino, the warming effect in the Pacific Ocean, confirming yet again the long-term trend of global warming

This map shows Earth’s average global temperature from 2013 to 2017 compared with a baseline average from 1951 to 1980, according to an analysis by NASA. Yellows, oranges, and reds show regions warmer than the baseline (Image by NASA’s Scientific Visualisation Studio)

2017 was one of the three hottest years on the planet since reliable recordkeeping started in the 1880s, three top scientific agencies said in separate statements on November 18. Scientists were surprised at the high surface temperatures that occurred last year despite the absence of El Nino, the Pacific Ocean’s warm phase.

The average global temperature was 1.1 degrees Celsius above the level seen during pre-industrial times, the World Meteorological Organization (WMO) said. The highest was in 2016, with 2017 and 2015 equal second, WMO said in a statement.

The earth’s global surface temperatures in 2017 was the second warmest since 1880, the National Aeronautics and Space Administration (NASA) said on January 18, trailing only the higher global average temperatures in 2016. Global average temperatures in 2017 were 0.9 degrees Celsius warmer than the mean between 1951 and 1980, according to scientists at NASA’s Goddard Institute for Space Studies (GISS) in New York.

“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,” said GISS Director Gavin Schmidt.

In another analysis by the National Oceanic and Atmospheric Administration (NOAA), also released on January 18, 2017 was the third-warmest year. The minor difference in rankings is due to the different methods used by the two agencies to analyse global temperatures, particularly how they measure temperatures in the Arctic, although over the long-term, the agencies’ records remain in strong agreement, they said. Both analyses show that the five warmest years on record all have taken place since 2010.

The planet’s average surface temperature has risen more than 1 degree Celsius in the past 100 years, a change driven largely by increased emissions of carbon dioxide and greenhouse gases into the atmosphere. Last year was the third consecutive year in which global temperatures were more than 1 degree Celsius above late nineteenth-century levels.

High carbon era

“Carbon dioxide remains in the atmosphere for centuries and in the ocean, where it acidifies the water, for even longer,” said WMO Secretary-General Petteri Taalas. “It is now above the symbolic and significant level of 400 parts per million concentration in the atmosphere.”

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.

What took scientists by surprise was that even without an El Niño event, and with a La Niña starting in the later months of 2017, last year’s temperatures ranked between 2015 and 2016 in NASA’s records. NOAA found that in 2017, the average temperature across global land and ocean surfaces was 0.84 degrees Celsius above the 20th century average.

Significantly, all the 16 hottest years on record have been in this century, except 1998, when there was a strong El Niño. The year 2017 also marks the 41st consecutive year since 1977 with global land and ocean temperatures above the 20th century average, NOAA said in its statement.


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