WASHINGTON (AP) -
Earth last year wasn’t quite as hot as 2016’s record-shattering mark, but it
ranked second or third, depending on who was counting.
Either way,
scientists say it showed a clear signal of man-made global warming because
it was the hottest year they’ve seen without an El Nino boosting
temperatures naturally.
The National
Oceanic and Atmospheric Administration and the United Kingdom’s
meteorological office on Thursday announced that 2017 was the third hottest
year on record. At the same time, NASA and researchers from a nonprofit in
Berkeley, California, called it the second.
The agencies
slightly differ because of how much they count an overheating Arctic, where
there are gaps in the data.
The global average
temperature in 2017 was 58.51 degrees (14.7 degrees Celsius), which is 1.51
degrees (0.84 Celsius) above the 20th century average and just behind 2016
and 2015, NOAA said. Other agencies’ figures were close but not quite the
same.
Earlier, European
forecasters called 2017 the second hottest year, while the Japanese
Meteorological Agency called it the third hottest. Two other scientific
groups that use satellite, not ground, measurements split on 2017 being
second or third hottest. With four teams calling it the second hottest year
and four teams calling it third, the United Nations’ World Meteorological
Organization termed 2017 a tie for second with 2015.
“This is
human-caused climate change in action,” said Nobel Prize winning chemist
Mario Molina of the University of California San Diego, who wasn’t part of
any of the measuring teams. “Climate is not weather, (which) can go up and
down from year to year. What counts is the longer-term change, which is
clearly upwards.”
Which year is
first, second or third doesn’t really matter much, said Princeton University
climate scientist Gabriel Vecchi. What really matters is the clear warming
trend, he said.
NOAA’s five hottest
years have been from 2010 on.
During an El Nino
year - when a warming of the central Pacific changes weather worldwide - the
globe’s annual temperature can spike, naturally, by a tenth or two of a
degree, scientists said. There was a strong El Nino during 2015 and 2016.
But 2017 finished
with a La Nina, the cousin of El Nino that lowers temperatures. Had there
been no man-made warming, 2017 would have been average or slightly cooler
than normal, said National Center for Atmospheric Research climate scientist
Ben Sanderson.
On the other hand,
NASA calculated if the temperature contributions of El Nino and El Nina were
removed from the global data through the years, 2017 would go down as the
hottest year on record, NASA chief climate scientist Gavin Schmidt said.
Carbon pollution is
like putting the Earth on an escalator of rising temperatures, with natural
variation such as El Nino or the cooling effect of volcanoes like hopping up
or down a step or two on that escalator, scientists said. Not every year
will be warmer than the last because of natural variations, but the trend
over years will be rising temperatures, they said.
The observed
warming has been predicted within a few tenths of a degree in computer
simulations going back to the 1970s and 1980s, several scientists said.
It has been 33
years since the last month that the globe was cooler than normal, according
to NOAA.
Northern Illinois
University climate scientist Victor Gensini has never lived through a month
or year that wasn’t hotter than normal.
“I look at pictures
of the great winters of the late ‘70s from my parents and wonder if I’ll
ever experience anything like that in my lifetime,” said Gebsini, who’s 31.
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