This is the blog post I hate
to write.
Because it’s about worst
nightmares coming true.
About tipping points and
points of no return.
We’re there.
Polar
ice sheet doomed, the headline read. West Antarctic Ice Shelf on a path to
disintegration - 13 more feet of water in the oceans.
Anyone following polar ice
science has seen the trend for years.
Accelerating glacier flow. Ice
shelf break-up. Going on since the 1990s, and intensifying since 2000. Arctic
summer sea ice has been fading at an unexpected rate as well. But sea ice is in the sea so it does not
raise sea levels. Antarctica and Greenland
ice above sea level does.
How far can seas rise? Consider the Eemian, the warm period before
the last ice age. In the must-read “Assessing
‘Dangerous Climate Change’” published in December, climate scientist James
Hansen and his team note that the Eemian saw global warming of at most 3.6˚F above temperatures around
1920. Since then the planet has heated 1.1˚F. On the current trajectory global warming will
exceed 3.6˚F by the
end of this century.
What did Eemian sea levels
look like? At their peak, they were 30
feet higher than today’s. The rise did
not occur gradually. Hansen et al note that
at least 10 feet rapidly piled on in the late Eemian, “suggesting the
possibility that a critical stability threshold was crossed that caused polar
ice sheet collapse.” In other words, high
temperatures eventually crack and rapidly dissolve ice sheets.
That is the greatest danger
posed by the West Antarctic Ice Shelf (WAIS). The study in the news was from a
scientific team led by Eric Rignot of NASA.
They examined retreat of the largest WAIS glaciers. Scientists
found that the process has now become unstoppable. The shelf is in the
ocean’s realm anchored to the seabed. But warm ocean waters and increased winds
are undermining the grounding from the bottom.
“. . . we have witnessed
glacier grounding lines retreat by kilometres every year, glaciers
thinning by meters every year hundreds of kilometres inland, losing
billions of tons of water annually, and speeding up several percent every year
. . . “
Loss of those big glaciers “will likely trigger the collapse of
the rest of the West Antarctic ice sheet, which comes with a sea level rise of
between three and five meters (10-16 feet). Such an event will displace
millions of people worldwide.”
At current rates the big glaciers would be gone in 200
years. But rates are accelerating and
rapid ice sheet collapse is in the cards.
Our children’s generation could well see WAIS go into its death spiral, maybe
even some of the younger members of this generation.
Cry for the melting cryopshere, and for low-lying coastal cities
from Venice to New Orleans.
Ice disintegration doesn’t
stop with West Antarctica, but moves into the big daddy of ice sheets, East
Antarctica. Go a little further back in
time to around three million years ago when temperatures were 5.4˚F above the current geologic
era, a point the Earth could reach in a century. Sea levels were elevated 50-80 feet over those
of today.
Hansen et al write, “Such sea
level rise suggests that parts of East Antarctica must be vulnerable to
eventual melting with global temperature increases of only a few degrees
Celsius. Indeed, satellite gravity data
and radar altimetry reveal that the Totten Glacier of East Antarctica, which
fronts a large ice mass grounded below sea level, is now losing mass.”
Rignot
notes that Totten alone contains the equivalent of 22 feet of sea
level. Our coming generations are facing
radically higher sea levels.
Can we stop this
somewhere?
I caught up with Rignot the
other day to pose a question: Assume a global political-economic miracle spurred by
findings such as that of your group. The world wakes up, finally, and declares
an effort on the scale of World War II. We do what Hansen et al prescribe
in their December article. We begin six percent annual reductions in carbon emissions,
hold total industrial era emissions to 500 billion metric tons, and pull
another 100 billion of the atmosphere into vegetation and soils. Does
this avoid the eventual deterioration of WAIS? Or is this already baked
into the cake?
Eric responded, “We have already blown the fuse but the
dismantling of West Antarctica could go faster if we keep heading this way. A
slow down of warming would likely help get there slower.”
So there it is. We can at
best slow the disintegration of the WAIS.
With a campaign of radical carbon reduction we can give our coming
generations a fighting chance to achieve a managed retreat to higher ground.
But can we stop the disintegration of Greenland and East
Antarctica? A new
study shows that Greenland glaciers are more vulnerable to melting than we
thought. Valleys underlying the glaciers are beneath the level of warming seas
further inland than was previously known.
Greenland ice equals 20 feet of sea level, East Antarctica around 190.
How long before we read the news we’ve “blown the fuse” on
substantial parts of these ice sheets?
We don’t know. But the evidence from the way this planet looked when
temperatures were only a few degrees warmer says we are perilously close.
This all points to an undeniable conclusion that a dramatic carbon
reduction effort is needed on the order of what Hansen et al prescribe in their
article. It may seem completely beyond
the realm of political and economic possibility to move to carbon cuts of six
percent annually. It also seemed wild
when Franklin Delano Roosevelt in 1940 called on the U.S. to build 50,000
planes a year when we were only making a few hundred. By 1942, the nation reached FDR’s
target.
It’s going to take leadership.
To stay relevant in the face of ever worsening climate impacts the
climate movement needs to start advancing climate solutions equal to the
perilous challenges we face. Elected leaders need to step up, honestly address
the desperate climate situation and forward the global carbon reduction
campaign that must be undertaken.
We are already leaving our kids and their coming generations with
some deeply dangerous legacies. If we
are to redeem our memory in the eyes of those who come after us, we need to act
now in proportion to the immensity of the challenge.
I close with the words of Martin Luther King Jr. addressing
Riverside Church in April 1967 when he broke silence and took an active stand
against the Vietnam War. His words could not be more fitting to our generation’s challenge:
“We are now faced with the fact, my friends, that
tomorrow is today. We are confronted with the fierce urgency of now. In this
unfolding conundrum of life and history, there is such a thing as being too
late. Procrastination is still the thief of time. Life often leaves us standing
bare, naked, and dejected with a lost opportunity. The tide in the affairs of
men does not remain at flood -- it ebbs. We may cry out desperately for time to
pause in her passage, but time is adamant to every plea and rushes on. Over the
bleached bones and jumbled residues of numerous civilizations are written the
pathetic words, ‘Too late.’ There is an invisible book of life that faithfully
records our vigilance or our neglect. Omar Khayyam is right: ‘The moving finger
writes, and having writ moves on.’”
p.s. Here’s a great
video explaining why WAIS is on the way out.
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