Natural climate variability explains almost half of Arctic sea ice loss
Manmade climate change alone doesn't explain the dramatic loss of sea
ice in the Arctic. According to new analysis by scientists at Lawrence
Livermore National Laboratory, natural climate variability has
accelerated Arctic sea ice loss over the last several decades.
Researchers used a variety of climate models and an analytical method
known as "fingerprinting" to determine which factors best explain
changes in Arctic sea ice.
The new analysis -- detailed this week in the journal Nature Geoscience
-- suggests natural climate fluctuations, including El Niños and La
Niñas patterns, account for 40 to 50 percent of sea ice loss in the
Arctic.
"Internal variability can enhance or mute changes in climate due to
greenhouse gas emissions. In this case, internal variability has tended
to enhance Arctic sea ice loss," said Stephen Po-Chedley, an LLNL
climate scientist, said in a news release.
Most climate models predict less sea ice loss than has been observed in
recent years. The latest analysis suggests natural atmospheric patterns
help explain the accelerated melting.
"It is important to note that individual runs do show large changes in
sea ice that are comparable to observed sea ice changes," Po-Chedley
said. "In these simulations, like in the real world, Arctic sea ice loss
was enhanced by natural climate variability. When natural variability
is taken into account, Arctic sea ice loss is quite similar across
models and observations."
Over the last decade, Arctic sea ice maximum and minimum extents have
routinely set new record lows. The latest research suggests those losses
are the result of both human-caused global warming and natural climate
variability.
But natural atmospheric patterns can also be influenced by greenhouse
gas emissions. Previous research has shown increases in climate
change-caused marine heat waves can encourage prolonged El Niño
patterns.
"Climate change is influencing the traditional dynamics of El Niño and
La Niña events as well as their impacts," WMO Secretary-General Petteri
Taalas said in a statement earlier this year.
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