As catastrophes go, sea level rise is probably fairly low on everybody's list. The most dire effects will be felt over many decades or centuries, whereas the jobless are wondering what's going to happen to them next month or next year. Still, expanding oceans provide a longer term perspective on where humanity stands with respect to Planet Earth.

Today's title comes from a 2009 book The Rising Sea by Rob Young and Orrin Pilkey. (Parts of the book are available online.) In their last report (AR4, 2007) on global warming, the bureaucrats at the IPCC left out a rather important factor regarding sea level change—

Given the complexities of forecasting how much the melting of the Greenland and West Antarctic ice sheets will contribute to increases in global sea level, the IPCC chose not to include these giant ice masses in their calculations, thus ignoring what is likely to be the most important source of sea level rise in the 21st century. Arguing that too little was understood about ice sheet collapse to construct a mathematical model upon which even a rough estimate could be based, the IPCC came up with sea level predictions using thermal expansion of the oceans and melting of mountain glaciers outside the poles. Its results were predictably conservative — a maximum of a two-foot rise this century — and were even a foot lower than an earlier IPCC report that factored in some melting of Greenland’s ice sheet.

Whoops! Young and Pilkey (and many others) decided to include what the IPCC left out. Their conclusion? Societies should prepare for 7 feet (2.13 meters) of sea level rise by 2100!

... there should be no confusion about the serious threat posed by rising sea levels, especially as evidence has mounted in the past two years of the accelerated pace of melting of the Greenland and West Antarctic ice sheets.

The message for the world’s leaders and decision makers is that sea level rise is real and is only going to get worse. Indeed, we make the case in our recent book, The Rising Sea, that governments and coastal managers should assume the inevitability of a seven-foot rise in sea level. This number is not a prediction. But we believe that seven feet is the most prudent, conservative long-term planning guideline for coastal cities and communities, especially for the siting of major infrastructure; a number of academic studies examining recent ice sheet dynamics have suggested that an increase of seven feet or more is not only possible, but likely. Certainly, no one should be expecting less than a three-foot rise in sea level this century.

We need to put this in perspective. What does a 1 meter (= 3.28 feet) rise in sea level portend?

If shorelines retreat naturally, a one meter rise would inundate 20,000 square kilometers (7,700 square miles) of dry land, an area the size of Massachusetts; rises of 50 and 200cm would result in losses of 13,000 and 31,000 square kilometers (5,000 and 12,000 square miles), respectively. Seventy percent of the losses would occur in the southeast, particularly Florida, Louisiana, and North Carolina; the eastern shores of Chesapeake and Delaware Bays would also lose considerable acreage.

Although I haven't read their book, it seems clear that 7 feet is a planning number based on our large uncertainties regarding ice sheet (West Antarctica, Greenland) dynamics as the world warms. Previous forecasts cited in The Copenhagen Diagnosis are shown below.

100 centimeters = 1 meter. Forecasts for 2100 are anywhere from 0.5 to 1.4 meters, with a projected rise by 2200 of about 3.5 meters in the worst case

What specific areas will be inundated? Coastal cities, obviously—

The world’s major coastal cities will undoubtedly receive most of the attention as sea level rise threatens infrastructure. Miami tops the list of most endangered cities in the world, as measured by the value of property that would be threatened by a three-foot rise. This would flood all of Miami Beach and leave downtown Miami sitting as an island of water, disconnected from the rest of Florida. Other threatened U.S. cities include New York/Newark, New Orleans, Boston, Washington, Philadelphia, Tampa-St Petersburg, and San Francisco. Osaka/Kobe, Tokyo, Rotterdam, Amsterdam, and Nagoya are among the most threatened major cities outside of North America.

What should we go about this? I doubt we'll do much of anything, because human life on Earth is going to be such an unholy mess by 2100 that most people—cunning, well-armed bands of marauders who have managed to stay alive—will be lucky if they can scavenge enough edible food & potable water to get them through the day. And there won't be any bounty of the sea.

Still, Young and Pilkey feel compelled to include the Obligatory Hope—

Despite the dire facts, the next century of rising sea level need not be an economic disaster. Thoughtful planning can lead to a measured retreat from vulnerable coastal lowlands. We recommend the following:

• Immediately prohibit the construction of high-rise buildings and major infrastructure in areas vulnerable to future sea level rise. Buildings placed in future hazardous zones should be small and movable — or disposable.
• Relocation of buildings and infrastructure should be a guiding philosophy.
  Instead of making major repairs on infrastructure such as bridges, water supply, and sewer and drainage systems, when major maintenance is needed, go the extra mile and place them out of reach of the sea.
• Etc.

I've seen this kind of thing many, many times before, so I decided to generalize it—

Despite the dire situation, _______ need not be an economic disaster. Thoughtful planning can lead to happy solution _______. Toward that end, we recommend the following:

• Impossible task 1
• Impossible task 2
• ...
• Impossible task n

How high will sea level rise by 2050? That's a scant 40 years from now, so it's a little easier to envision. My best guess is that 0.5 meters (1 foot, 7.68 inches) is the worst case. Paleontologist Peter Ward, in a burst of fancy in his new book The Flooded Earth, envisions a world where sea level rises a full meter by 2050. Thus we would lose coastal areas the size of Massachusetts. Peter, fear mongering is best left to non-scientists who have no idea what they're talking about. (And I've read most of Ward's books.)

The danger is that ice sheet responses to a warming Earth really are uncertain, and there is indeed evidence that melting & breakup has proceeded faster than was previously thought possible. If you're keeping track, sea level rise should be on your disaster list, even if you have more pressing concerns at the moment.