Philip Conkling et al.
The Fate of Greenland

Prepared by Michael Marien

argaiv1254


October 2012

Greenland Ice Melt: How Much? How Soon?


the-fate-of-greenland

The Fate of Greenland: Lessons from Abrupt Climate ChangePhilip Conkling (President, Island Institute in Maine),

Richard Alley (Prof of Geosciences, Penn State U), Wallace Broecker (Prof of Geology, Columbia U), and George Denton (Prof of Geosciences, U of Maine). Photographs by Gary Comer (deceased, 2006; founder, Land’s End direct mail).  Cambridge MA: The MIT Press, April 2011, 216p, $29.95 (with 72 color photos).


 

PERSONAL PROLOGUE: SUPERSTORM SANDY AND FEEDBACK LOOPS 

When this unusual, important, and somewhat non-technical book was first published in 2011, it was almost chosen as the GFB Book of the Month.  Instead, as a close runner-up, it went to the Recommended List, with several hundred other competing titles.  Yet, literally, the book would not go away.  Rather than retiring it to my bookshelf, it remained in my burgeoning pile of incoming books.  I cited it several times, recommended it to several people, and returned several times to look again at the haunting and strikingly beautiful photos of melting icebergs, shrinking glaciers, and increasingly bare earth of the world’s largest island.

Since then, I have considered promoting the Greenland book to “BOM” status, despite now being more than a year and a half old (which hardly matters, regarding this long-term and accelerating development).  Two “tipping points” have pushed this book to the fore.

In late October, the devastation of “Superstorm Sandy” to the coastal areas of New Jersey, New York, and Connecticut resulted from a  storm surge of up to 14 feet in some areas.  The New York Times (31 Oct 2012, A18) reported that scientists had warned about the perils of flooding for years.  Moreover, “after rising roughly an inch per decade in the last century, coastal waters in New York are expected to climb as fast as six inches per decade, or two feet by midcentury, according to a city-appointed scientific panel.”  Even before Hurricane Sandy, an eerily prescient 9/11-timed feature in the Times (“New York Is Lagging as Seas and Risks Rise, Critics Warn,” 11 Sept 2012, p1) noted the “accelerating” rate of sea level rise and more “frequent flooding” as an uncomfortable reality: “were sea levels to rise four feet by the 2080s, for example, 34% of the city’s streets could lie in the flood-risk zone, compared with just 11% now.” But reading the neglected Greenland book, which suggests a possible sea level rise of 24 feet if the Greenland ice sheet melts, the illustrative four-foot forecast for NYC may be severely understated by a factor of six—and this does not consider a melt of the West Antarctic ice sheet, which would add another 16-foot sea-level rise!

Obviously there are huge uncertainties ahead, but scenarios of a possible 24-40 foot rise in sea level in the next century—and perhaps even in a matter of decades—should not be ignored, despite being far beyond the conventional wisdom of today’s climate science.

The second “tipping point” is an article by John Carey in the Nov 2012 Scientific American (“Global Warming: Faster Than Expected?” pp. 50-55), which belies the question mark in the sub-title by stating that the latest data “show that the planet is changing faster than expected.”  Carey summarizes six “long-hypothesized feedback loops that may be starting to kick in… (and) may be pushing the earth into an era of rapid change.”  In brief, they are: 1) loss of sea ice, which allows the sun to warm ocean water more, which melts even more sea ice; 2) greater permafrost melting that puts more CO and methane in the atmosphere, in turn causing more permafrost melting; 3) expanded wetlands from increasing rainfall in the tropics, which potentially “could release as much, or more, additional methane as that from Arctic warming”; 4) vegetation changes that turn forests from CO2-absorbing carbon sinks into carbon sources from decomposing dead trees; 5) a very warm summer leading to massive fires pouring carbon into the atmosphere; 6) warmer ocean currents that could slow or stop the system driving global ocean currents: “that change could turn Greenland from cool to warm within a decade.” Imagine two or more of these feedback loops working together to accelerate climate change! [See Epilogue on the Arctic “Death Spiral.”]   A 24-40-foot rise in sea level seems inconceivable today, yet it increasingly becomes not a “wild card” but a “not-so-wild” card of, say, 10-40% probability by 2050.  And even this could be an understatement!

The prospects for increasingly rapid climate change require careful monitoring and frequent adjustment.  And thus The Fate of Greenland is given prominence here, with an expanded abstract and highlighted statements of significance.

 

GREENLAND THEN AND NOW

Greenland is the world’s largest island, 90% of which is covered by ice.  Its ice sheet—the largest outside of Antarctica—stretches almost 1,000 miles from north to south and is 600 miles from east to west.  “Historical research has clearly documented that Greenland has twice experienced dramatic and rapid shifts in climate during the last 1000 years of its history.” (p.1) The dates of the Norse settlement and occupation of Greenland, from the late 980s to 1410, neatly circumscribe most of the era that climatologists call the Medieval Warm Period.  As documented in Greenland’s ice core records, there is also evidence of scores of abrupt climatic changes in recent geologic history.  “A couple of dozen times over the last 100,000 years, a sudden warming occurred over Greenland, often 10°C (18°F) or even more, in roughly a decade or less.  Then gradual cooling was followed by fast cooling, a few centuries of really cold conditions, before another warming jump.” (p69)

Several research voyages sponsored by Gary Comer since 2001, all around Greenland’s coast and over its ice sheet, have documented a rapidly changing climate at every location visited.  “Greenland appears to be poised at the edge of another rapid climate change, which in the past has propagated climate change across both hemispheres.  Therefore, it is in all our interests to pay attention to Greenland, because in the fate of Greenland lie clues to the fate of the world. Greenland, in other words, matters.” (p.23; GFB emphasis)

Humans have become the biggest force in the climate system.  Most scientists believe that if we’re on the verge of a change in climate models from one of relative stability to instability, then continued loading of greenhouse gases into the atmosphere only increases the uncertainty and instability.   “We do not yet have the scientific sophistication to know the likelihood that an abrupt climate change will occur at any specific time in the future, but we now know that abrupt climate changes have repeatedly occurred in the past and that we are taking an enormous risk.” (p23)

 

THE FATE OF THE ICE SHEET

Scientists have calculated that if the Greenland ice sheet melts, sea level would rise seven meters—or about 24 feet—worldwide. In contrast, if the West Antarctic ice sheet melted, it would cause a five-meter—16-foot—sea level rise.  The huge East Antarctic ice sheet is believed to be too cold to change dramatically.” (p22)

“If the Greenland ice sheet melts, most all [sic.] of lower Manhattan would either need to be protected by dikes or would be underwater, and Florida’s coast would recede nearly to Orlando.  If warming also destroys the East Antarctic ice sheet and causes an additional 15-foot sea level rise worldwide, most of the state would disappear.” (p22)

“The big news is that worldwide temperature spikes occur when the global climate is changing modes.  At such times climates change with such stunning speed that adjustments, even by the rich and technologically sophisticated nations of the world, may barely mitigate the effects.  And for poor countries, the losses will likely be catastrophic.” (p22)  Climate change research has “elegantly demonstrated that the best we can hope for is gradual warming in response to rising carbon dioxide from our burning of fossil fuels.  Too often in the past, however, the climate has staggered drunkenly, a phenomenon that is deeply worrisome because faster and unexpected changes are harder to deal with and responding to them is much more costly.  The research described in this volume has established unequivocally that these sudden stumbles are real.” (p23)

The Greenland ice sheet now is high and cold in the middle, lower and warmer on the edges.  If too much ice leaves, the center will be lowered, getting warmer.  At some point, thinning from warming will cause enough more warming so that the ice sheet won’t survive.  Competition between thinning from warming and thickening from more snowfall makes a difficult tipping point to predict.  But the history of the ice sheet suggests that there is such a tipping point.  “We don’t believe that the ice sheet could fully disintegrate faster than many centuries, but we might cause enough warming within a few decades to cross the threshold leading to ice sheet loss.” (p182)  Because different positive feedbacks amplify each other, “the slight chance of a really big change cannot be excluded.” (p170)  A two-sided view of things getting better or worse is overly simplistic because there are many sides, especially the possibility that things might end up a lot worse due to the lop-sidedness of the uncertainties.  “The future could be better than mainstream scientific projections, but ‘a little better’ is balanced against ‘a little worse’ or ‘a lot worse’.” (p183)

 

CAUTIOUS FORECASTS

 As ocean models become better, they indicate less possibility that Greenland’s melt water will arrive fast enough to truly disrupt the ocean conveyor.  The most recent assessment by the IPCC gave a >90% chance that “nothing drastic would happen to the conveyor over at least the next century.  That is good news.  But 90% is not 100%...and the North Atlantic is not the only place where abrupt changes might be possible.”(p191)

“Methane locked in seabed sediments will probably behave itself, leaking out slowly if at all, but we cannot absolutely guarantee that there will not be large and rapid releases.” (p192)

Significantly, these and other possible tipping points all slant in the directions that would cause harm to economies and ecosystems, with losers substantially outnumbering winners. And we do not see any evidence for tipping points to the other side that would suddenly jump us into a wonderful climate with winners greatly outnumbering losers.” (p192)

“We have high scientific confidence that the world will warm, the dry zones will become drier and expand, the ice will melt, and millions and millions of people will be affected.  Although warming some very cold regions may create new winners…warming and drying appear poised to bring many more losers.”  (p195)

With the possibility of abrupt climate changes…we must recognize the possibility that we have greatly underestimated the coming damages of climate change. However, we do not find evidence that we have greatly overestimated the damages.”  (p196)

“Recent assessments of abrupt climate changes have concluded that no single type of abrupt change is considered likely.  We don’t expect a North Atlantic conveyor shutdown, or a belching of methane, or a sudden collapse of a big ecosystem, or a sudden ice-sheet collapse, but all appear possible.” We cannot predict with current information that Earth will soon jump far to the bad side.  But “it is also true that the uncertainties are dominantly on the bad side.” (p200)

 

COMMENT

The authoritative assessment of Greenland ice by four leading climate scientists who have visited the region many times in the past decade.   They skillfully and quite properly deal with the many uncertainties.  It does not yet seem likely that Greenland ice melt will rapidly proceed in the decades ahead.  But, especially considering the feedback loops that now seem to be underway, the possibility of substantial ice melt—and sea level rise well beyond current expectations—appears to be more than that of a classic “wild card” (2%, from a joker in a deck of cards), and more in the “not-so-wild card” range of 10-40%.  The outlook deserves careful monitoring, with annually updated scenarios, and perhaps a Delphi-like process where a panel of climate scientists assign rough probabilities.  If  current trends continue, or accelerate, the “not-so-wild card” assessment of Greenland’s ice could become a “probable” development, if not “near certain.”

Co-author Richard Alley of Penn State U is also author of Earth: The Operator’s Manual (W.W. Norton, April 2011, 479p), the book companion to a PBS documentary.  Co-author Wallace Broecker is the author of numerous books and articles on climate such as The Great Ocean Conveyor: Discovering the Trigger for Abrupt Climate Change (Princeton, Feb 2010, 154p), and issued an early warning in  “Climate Change: Are We on the Brink of a Pronounced Global Warming” (Science, 8 Aug 1975).

ALSO SEE The Flooded Earth: Our Future in a World Without Ice Caps by U of Washington geologist Peter D. Ward (Basic Books, July 2010, 272p), who shows what our world will look like in 2050, 2100, and 2300, warning that a 4oF increase in global temperature could raise sea levels by 30 feet by 2100, and that, even if we stop all CO emissions, seas will rise one meter by 2050 and 3 meters by 2100.

 

EPILOGUE: ARCTIC “DEATH SPIRAL”?

Shortly after completing the above review, the Dec 2012 issue of Scientific American arrived, with a one-page essay by Peter Wadhams (Prof of Ocean Physics, U of Cambridge) on the likely Arctic “death spiral” and the “urgent” need for geoengineering to save the sea ice by lowering surface temperatures (p12).  Read closely what Wadhams writes (emphasis added):

* * *

“From space the top of the world now looks blue instead of white.  Things are worse than appearances would suggest, however. What ice is still left is thin—average thickness dropped 43% between 1976 and 1999, sonar measurements show.  By 2015, at this rate, summer melting will outstrip the accumulation of new ice in winter, and the entire ice cover will collapse.

Once summer ice goes away entirely, the physics of latent heat will make it very difficult, if not impossible, to get it back.  We will have entered what Mark C. Serreze, director of the National Snow and Ice Center at the University of Colorado at Boulder, calls the Arctic “death spiral”  Once ice yields to open water, the albedo—the fraction of solar radiation reflected back into space—drops from 0.6 to 0.1, which will accelerate warming of the Arctic.  According to my calculations, the loss of the remaining summer ice will have the same warming effect on the earth as the past 25 years of carbon dioxide emissions. Because a third of the Arctic Ocean is composed of shallow shelf seas, surface warming will extend to the seabed, melt offshore permafrost and trigger the release of methane, which has a much greater warming effect than CO2. A Russian-U.S. expedition led by Igor Semiletov has recently observed more than 200 sites off the coast of Siberia where methane is welling up from the seabed.”

The Wadhams essay nicely complements the Nov 2012 article by John Carey  in Scientific American on global warming feedback loops from melting sea ice and release of methane, mentioned in the Prologue to this review.   Obviously, the time has arrived to seriously think about scenarios and the probable fate of Greenland’s ice sheet.

 
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