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A28 SCIENCE
Thursday 12 december 2019

This Jan. 18, 2019 file photo shows a cyclist amidst morning
smog in New Delhi, India.
Associated Press

Study finds

climate simulations

are mostly accurate

In this Aug. 16, 2019, file photo, large icebergs float away as the sun rises near Kulusuk, Greenland. By SETH BORENSTEIN
Associated Press AP Science Writer
WASHINGTON (AP) — The computer models used to
simulate what heat-trapping gases will do to global
Arctic habitats and cultures temperatures have been pretty spot-on in their pre-
dictions, a new study found.
on thin ice as region warms After years of hearing critics blast the models’ accu-
racy, climate scientist Zeke Hausfather decided to see
just how good they have been. He tracked down 17
By CHRISTINA LARSON The past two years saw re- “We look for the return of models used between 1970 and 2007 and found that
AP Science Writer cord low levels of sea ice — the sea ice every fall sea- the majority of them predicted results that were “indis-
WASHINGTON (AP) — Rising frozen seawater — floating son,” wrote 10 representa- tinguishable from what actually occurred.”
temperatures and shrink- on the Bering Sea during tives of the region’s more “By and large our models have gotten it right, plus or
ing snow and ice cover in winter, the report found. than 70 indigenous com- minus a little bit,” said Hausfather, a University of Cali-
the Arctic are endanger- And the habitats of fish on munities. “The ice provides fornia, Berkeley scientist who is climate and energy
ing habitats, fisheries and which commercial fisheries access to seals, whales, director at the Breakthrough Institute. “If they get it
local cultures, according and indigenous groups de- walrus, fish, crabs and wrong, it’s slightly on the warm side, but I wouldn’t
to a report issued Tuesday pend have shifted north- other marine life for our read too much into that.”
by the National Oceanic ward, according to the subsistence harvests.”The Ten of the 17 were close to the temperatures that ac-
and Atmospheric Adminis- report released at the an- communities once saw the tually happened, said Hausfather, lead author of a
tration. nual meeting of the Ameri- ice in the northern Bering study in Wednesday’s journal Geophysical Research
“A lot of people think of can Geophysical Union. Sea during eight months Letters.
the Arctic as being a far- “Fishing industries are built of the year, but now they But scientists actually got the physics right even more
away place, but the loss of around the assumption only see it for three or four than that, Hausfather said. That’s because they make
ice is affecting people now that fish will be in a certain months, the report found. two main assumptions when they model what will
— it’s changing peoples’ place at a certain time, Meanwhile, a new scien- happen in the future. One is the physics of the atmo-
lives,” said Don Perovich, but that’s changing in re- tific paper published Tues- sphere and how it reacts to heat-trapping gases. The
a Dartmouth College geo- sponse to a rapidly chang- day in the journal Nature other is the amount of greenhouse gases put into the
physicist who contributed ing Arctic,” said Waleed found that the melting of air.
to the report. “It isn’t just a Abdalati, an environmen- Greenland’s ice sheet has A few times, scientists were wrong in their predictions
bunch of cold statistics.” tal scientist at the University accelerated. The melting about the growth of carbon pollution, saying there
The Bering Sea, which lies of Colorado-Boulder who is now seven times faster would be more of the gases than there actually were,
between Alaska and Rus- was not part of the report. than in the 1990s. Hausfather said. If they got the amount of heat-trap-
sia, is one of the world’s For the first time, the U.S. Less ice means feeding ping gases wrong, they then got the temperatures
two most productive fisher- agency’s annual “Arctic disruptions for many Arctic wrong.
ies. But the Arctic region is Report Card” includes ob- species. Polar bears stalk So Hausfather and colleagues, including NASA cli-
warming more than twice servations from indigenous their prey, including seals, mate scientist Gavin Schmidt, looked at how well the
as fast as the rest of the groups who hunt and fish in on ice. Ivory gulls scav- models did on just the pure science, taking out the
planet, the report found. the region. enge on ice for scraps of emissions factor. On that count, 14 of the 17 computer
those hunts, as well as for models accurately predicted the future.
small fish and other crea- The scientists also gave each computer simulation a
tures. “skill score” that essentially gave a percentage grade
“Birds are migrating to to each one. The average grade was a 69%.
the Arctic and not finding One of the earliest computer models, made in 1970,
the food they need,” said got a 91%. What’s so impressive about that is that at
Matthew Druckenmiller, a the time, climate change wasn’t noticeable in the
scientist at the University yearly temperature records like it is now, Hausfather
of Colorado Boulder’s Na- said.
tional Snow and Ice Data Stanford University climate scientist Noah Diffen-
Center and one of the baugh, who wasn’t part of the study, called the work
NOAA report editors. q creative and the results striking.q