A New Primer on Sea Level

by |March 7, 2013

The threat of sea-level rise–actually, its ongoing reality–has been on many more minds since New York and surrounding areas were walloped during Hurricane Sandy by a record-high storm surge, abetted by a water level that has risen steadily over the last century. That level will keep rising if climate keeps warming, and so, probably, will the frequency of extreme weather. That is why the new book Rising Seas: Past, Present Future by geologist Vivien Gornitz is a timely and important contribution to helping people understand the issue.

Some basic facts and figures: Around the very warm time of dinosaurs, sea level was by some estimates a staggering 560 feet higher than today. During alternating ice ages and interglacials in the last million years or so, it has ranged from 400 feet lower (when a lot of water was locked up in ice) to 30 feet higher (when things melted). It has remained essentially stable for the last 7,000 years–pretty much the span of modern civilization. Some estimates are a little squishy, because many factors besides ice can influence sea levels, and confound measurements of it over space and time. Among them: tectonic processes and loading or unloading of ice sheets that raise or lower the land itself; expansion and contraction of the oceans as they heat or cool; and currents and winds that pile up more water in some places but push it away in others. We do know that sea level around New York City has climbed 1.4 feet since 1856–probably faster than the average global sea level rise. The global rate from 1993-2012 was about 3.1 millimeters, or 12 hundredths of an inch per year–attributed by most if not all earth scientists to global warming. The big unknown is what to expect in the future.The Intergovernmental Panel on Climate Change has thus far estimated a rise of 7 to 23 inches by 2100–but observations of what is happening now suggest that the slow-moving IPCC consensus already is way behind the curve. Ever better-documented melting of polar ice sheets, which IPCC does not account for, means it may be more like 2.5 feet to as much as 6.2 feet. If the vast Greenland and West Antarctic ice sheets were to melt completely in that time, levels would rise some 33 feet–but few if any scientists think such a thing that could happen so fast.

Such big ranges in the projections may be one reason many ordinary people shrug at climate change. Every week, a new study comes out with a new number, and that is confusing. Most just want to know the definitive answer, and after a while, if they don’t hear it, they figure scientists don’t know what they are talking about. That of course is not true; science almost always is a process of reducing uncertainty in what we think we know–not suddenly declaring that we now know it all. Putting individual pieces of information into context and making clear the amount of uncertainty is key, and the book does this admirably. Furthermore, few are more qualified than Gornitz to carry it off. A special research scientist at Columbia University’s Center for Climate Systems Research, and the NASA Goddard Institute for Space Studies, she has been looking seriously at the subject for decades. In the 1990s, she began to warn that the metro area needed to harden its low-lying subways, roads and airports in places like lower Manhattan, Jersey City and the Rocakaways against the oncoming effects of rising seas and storms that could whip them up. She and colleagues have been proven completely right; no matter what the final number is, it’s a problem that has to be confronted.

The book is marketed as a text, but it is an easily readable, all-around primer for anyone who would like to know as much as anyone knows about this subject. Among other things, it has a fascinating chapter on the visible effects of sea-level rise, from disappearing rural barrier island communities along the U.S. east coast and the Navy town of Norfolk, Va., to a disintegrating Inuit coastal village in Alaska, and on to sinking Pacific island nations, and effects on natural systems such as freshwater aquifers coral reefs. Another chapter explores efforts to keep water out with of big cities like Venice, London and Rotterdam with gigantic engineering undertakings such as sea gates and floating buildings.

Those cities are going with the flow, and places like New York will likely follow suit, or be lost. “We are moving toward an increasingly warmer and, quite a likely, a more acquatic planet,” says Gornitz. “We would do well to take heed and begin preparations to stem the oncoming tide.”


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