What are the ramifications for shorelines around the world if predictions?

What are the ramifications for shorelines around the world if predictions about rising sea levels due to global warming actually come true?

—James Florino, Palm Beach, FL

Sea level rise, and the accompanying loss of shoreline, promises to be one of the most devastating results of global warming. A recent report by the Intergovernmental Panel on Climate Change, a group of leading atmospheric scientists, forecasts a global sea level rise of between seven and 23 inches by 2100. This they foresee due to the greenhouse gases we have already pumped into the atmosphere—even if we start cutting back now. Such dire but realistic predictions are based on computer models that factor in the heating and expansion of the ocean, the melting of polar ice sheets, and storm surges that can affect tides by a foot or more.

What does this mean for shorelines around the world? Simply put, existing shorelines, especially in low-lying areas, will become submerged—a sea level rise of less than half an inch can cause shoreline retreat upwards of four feet—forcing inhabitants to relocate their homes, businesses and ways of life. Perhaps the most striking example of this type of upheaval is already underway in Bangladesh, a low-lying country of 140 million people. According to the World Bank, an international lending and development agency, sea level rise will likely inundate as much as 20 percent of the country”s habitable land, affecting as many as 30 million people already living on the edge of survival. As much as a third of the country”s rice crop will be lost, and natural treasures like the Sundarbans mangrove forest will be reduced to just a memory.

With about a third of the world”s people living within 60 miles of a shoreline, and 13 of the world”s 20 largest cities located on coasts, people are bracing for the worst beyond Bangladesh as well. Scientists fear that sea level rise, especially when combined with intense storms, could deliver a knock-out blow to areas already devastated by 2004″s Indian Ocean tsunami. China, India and Egypt are also expected to experience major flooding. One result could be a humanitarian crisis as millions of so-called “climate refugees” could seek higher ground, perhaps across national borders where they are not welcome.

Here in the U.S., scientists fear rising sea levels could put a recovered New Orleans back under water, but this time permanently. In New York, stronger and more frequent hurricanes, also thanks to global warming, could combine with rising sea levels to essentially put most of Manhattan and outlying areas under water, wreaking untold havoc for millions of people in the region. And in the San Francisco Bay Area, according to a report by the Bay Conservation and Development Commission and summarized in an article in the San Francisco Chronicle in February 2007, San Francisco”s sewage-treatment facility on Islais Creek and both San Francisco and Oakland airports could be under water.

With scientists uncertain about the amount of sea level rise to anticipate, municipal officials are working to get their cities ready in a number of ways, including “nourishing” beaches with additional sand and building overlapping layers of levees and sea walls. But engineers warn that already strained municipal budgets have no room for the staggering costs of buttressing entire cities against sea level rise, so planners will be forced to pick and choose to hopefully avert disaster. For the rest of us, it might be a good time to sell that waterfront vacation property that has appreciated so much in value in recent years.

CONTACTS: Intergovernmental Panel on Climate Change; World Bank-Bangladesh