SEA LEVEL RISE WILL BE FAR GREATER THAN PREDICTED

By guest blogger, Prof. James R Flynn FRSNZ.*

Jim FLynn2    NPTH cover

As Ben Strauss (Director of Climate Control) says “the 22nd century will become the century from hell.”

 Until very recently, scientific opinion included some who predicted only a very gradual rise in sea level over the remainder of this century: most of them less than a meter.  This was because sea level rise up to now has been caused mainly by thermal expansion.  As oceans get warmer the water expands but not too alarmingly.  The best science is now predicting a huge rise by the year 2100.  This is because of the fragility of the Polar Ice Caps.  It sets into motion a feedback mechanism that takes global warming out of human control. The Polar Ice acts as a gigantic set of mirrors that reflect heat back into space.  As they decline that raises the earth’s temperature, which melts more Polar Ice, which raises temperature further, and so we go.  The carbon emissions we send into the atmosphere become a junior player in global warming to the extent that after 2050, our efforts to cut them become swamped by the Polar Ice factor.  It is much easier to keep a glacier from decline than to restore it once it fragments, if only because that in itself creates temperatures that are too hot.

Polar Ice is not is not like a solid ice cube that comes out of your fridge and slowly melts on your bench. As DeContro and Pollard (2016) point out, in their article in Nature, when a glacier is near the sea, melting ice on top of it fractures it into a series of ‘cliffs’. The ice between them falls into the sea leaving sheer cliffs behind. These cannot support their weight, and suffer from ‘cliff collapse’ that sends them into the sea as well. Moreover, some ice is strategically placed to keep other ice from sliding into the sea. In the West Antarctic, the Thwaites Glacier acts like a cork that holds back other glaciers that rest on a seabed that slopes toward the sea. It is melting fast and when it goes the others will follow it into the ocean. In the Arctic, sea ice plays this role and as it melts, the land ice it encircles will no longer be impeded from drifting toward the ocean.

I have focused on Polar land ice but note that we must take into account the polar ice that presently rests on the sea.  It may seem less significant because when it melts, it does not directly raise sea levels (it is already displacing its volume in the sea).  But when it is gone that is another huge mirror gone.  Notz and Stove (2016) predict that all Arctic sea ice (not land ice) will disappear by the year 2050.

James Hansen and his team have integrated the effect of glacier ice loss into a new and more comprehensive model of sea level rise.  It gives estimates with a median of 3.5 meters (scenarios range from 2 to 5) by the year 2100.  As Ben Strauss (Director of Climate Central) says, even a low estimate promises that the 22nd century will become the century from hell. If sea level is rising exponentially, then after 2100 the rise will be huge for each decade – somewhere between 0.80 and 2.73 meters between 2100 and 2110 alone and nightmarish after that. Planning to move inland will become a panic unless cities are put on roller skates.

To illustrate what sea-level rise implies, a rise of even 2.6 meters would put large percentages of American cities under water:  New Orleans 93, Galveston 82, Atlantic City 80, Miami 46, Norfolk 43, St. Petersburg 40, Jersey City 33, Charleston 30, Savannah 24. New York City would lose ‘only’ 15 per cent, so only about 1.26 million people would be directly affected (really more with population growth).

In sum, unless we abolish coal today, oil in ten years, and national gas in 20, the race to avoid unacceptable temperature and sea level rise has been lost. The only solution is to use a benign form of climate engineering to hold temperatures at their present level and give us 50 years to eliminate emissions.  I will explore alternatives in my next posting.

*  James R. Flynn is Emeritus Professor of Political Studies in New Zealand and author of 16 books including a series on the problems of the modern world, among which he considers climate change to be the most important. His book, No Place To Hide, attracted the following praise:
‘A broad-ranging view of the critical issues facing our planet written in an easy to understand non-technical manner’ — Jay Zwally, Maryland Earth Sciences and NASA Goddard Space Flight Centre.
‘A great read. A massive amount of information well organized and expressed’  — Sir Alan Mark, FRSNZ, Knight of the N. Z. Order of Merit.
‘Wonderful, for the first time I have read an unbiased overview of the science behind global warming’ — Rolf Dobelli, Author of The Art of Thinking Clearly.

 

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