Leveling on Sea Level

Take "maybe" out of concern about rising sea level. Forecasts of how high manmade global warming could raise the ocean by the year 2100 are iffy. But for many coastal dwellers the challenge of a rising sea is already upon them. They need to respond now rather than wonder about an uncertain future threat.

That's the perspective from which to view the recent National Environmental Trust video showing how much of Cape Cod, Mass., and neighboring islands could be inundated over the next century. Many a beach and beachside dwelling could disappear as global warming melts glaciers and expands sea water. It's a worst case scenario using the upper range of computer-generated climate forecasts to make the point that people should take global warming seriously.

There's no need for hype. Sea level has been rising 1 to 2 millimeters a year for centuries. A University of Maryland study published last year documents this long-term trend along North America's east coast.

Surges of storm-driven water and waves that ride on top of the surges reach higher on vulnerable cliffs and farther inland than they did a century ago. Areas that seemed safe back then now are vulnerable. Average sea level sets the base line height on which storm surges ride. Local tides raise or lower that base line depending on the set of the tide when a storm hits. Storm frequency and intensities haven't changed over this century. Neither have tidal ranges. But base line sea level has risen inexorably.

In many parts of the world local land subsidence adds to the problem. Some of the sinking is natural. Some is due to excessive tapping of ground water. Damming or diverting rivers can deprive their deltas of sediment that once had offset the sinking land.

We don't need theoretical projections to spur present action. While global warming could escalate the problem, the current danger from existing ocean rise is significant enough to merit far more attention than it's getting. New land and water management strategies are needed now. Development of vulnerable coastal areas should be tightly managed. In some cases, such as barrier islands, it should be banned as being vastly too expensive for individuals and society.