31 August 2019 | New Scientist | 39>CHRISTOPHER
MI
CHELIn 40 years, about 2.4 million
square kilometres of Arctic
sea ice has disappearedartificially brightening the surface of the ice to
reflect more sunlight; and cooling the Arctic air
by brightening the clouds to deflect sunlight.
All three ideas are forms of geoengineering:
intervention in the environment on a scale big
enough to counteract climate change. The
concept bothers many scientists because they
fear that the idea of a technological fix will
undermine efforts to cut carbon dioxide
emissions. “Well, we’re not making them
anyway,” says Cecilia Bitz, a sea ice physicist
at the University of Washington in Seattle.
“Maybe intervention would be positive,
showing that we have the capacity to improve
the environment.”
For those advocating such action, a big
concern is the methane already streaming out
of the seabed as microbes break down thawed
organic matter. “The fear is that this will grow
from being a set of methane plumes to an
outbreak,” says Wadhams. “So we need to bring
back the ice around the coastal seas, and that
might save us from a catastrophic methane
burst.” As well as this methane trapped under
the sea, an estimated 1 trillion tonnes of carbon
are in the top 3 metres of Arctic soils. If only a
small fraction of this reaches the atmosphere,
it will overwhelm any cuts in emissions we
have made. “It seems that nature offers us a
choice: instant methane from the seabed
giving us a huge immediate burst of warming,
or longer, slower warming from complex
chemical processes as terrestrial permafrost
thaws. Except that it’s not an ‘or’, it’s an ‘and’.”
The first potential solution comes from
Steve Desch, an astrophysicist at Arizona State
University. His plan is to build windmills that
pump seawater onto surface ice during the
winter, where it will freeze, thickening the sea
ice and extending its coverage. This method
was recently proposed to prevent the collapse
of the Antarctic ice sheet too.
Sea ice moves around, so Desch’s idea is to
locate the windmill-pumps on sea ice in the
north of the Arctic. This would help thicken
chunks of ice that are then protected from
melting when they move south. “While that
may seem like an impossible task, since the
Arctic is a very large place, we outlined a
mechanism, using simple, brute-force,
steampunk technology that is not impossible,
but enormous in scope,” he says. “It’s not like a
space mirror larger than the Earth or
something. It’s pretty simple, but just a big job.”
Desch has calculated that we would need“ It is no good
declaring a
climate
emergency
without
summoning
help. So here it
is: let’s refreeze
the Arctic”
hemisphere, resulting in more“blocked”
weather patterns, and corresponding
droughts, floods and heatwaves.
The global risks are huge. “Allowing the
Arctic to change in unrecoverable ways poses
an enormous safety risk to communities
around the world and could move the climate
system beyond our ability to recover,” says
Kelly Wanser, director of SilverLining, a
geoengineering NGO based in Washington DC.
Of course, we could have prevented the
Arctic from warming as much as it has if we
had cut global greenhouse gas emissions
when scientists first started advising us to
do so, decades ago. But we didn’t, and nor
are we now. “It’s a pious hope and anyway it
would take a while,” says Peter Wadhams,
head of the Polar Ocean Physics Group at
the University of Cambridge.
This is why a growing number of scientists
argue that, if we want to save the Arctic, we
need to intervene directly by manipulating its
climate system. There are three main proposals
for doing this: increasing the extent of sea ice;