Chilling Look at Greenhouse Effect’s Power to Alter Life

The single most-talked-about consequence of the greenhouse effect is probably the expected rise in global sea level as a result of polar melting. For the last few thousand years, the sea level “has risen so slowly that for most practical purposes it has been constant,” says James Titus, of the Environmental Protection Agency.

As a result, people have developed the coastlines extensively. Not just the beaches in Rio or the canals in Venice, but also the infrastructure of all major ports, around which have grown up most of the world’s great cities. And not just people: Marine plants and animals have taken the opportunity provided by sea-level stability to build huge communities such as the one in Chesapeake Bay. But, despite all this confidence, the sea level is not a given.

A hundred thousand years, ago, during the last interglacial period, it was 20 feet above current levels; at the height of the last Ice Age, when much of the world’s water was frozen at the poles, the sea level fell 300 feet.

Scientists estimate that the world’s remaining ice cover contains enough water so that, if it should all melt, the seas would rise about 75 meters, or nearly 250 feet.

This potential inundation is stored in the Greenland Ice Sheet (if it melts, it will raise the world’s oceans 20 feet), the West Antarctic Ice Sheet (another 20 feet), and East Antarctica (nearly 200 feet), with a smaller amount, perhaps 1.5 feet, in all the planet’s alpine glaciers combined.

The alpine glaciers, while small compared with the ice caps, are not small. Glaciers bordering the Gulf of Alaska, for instance, have been melting for decades and constitute a source of fresh water about the size of the entire Mississippi River system.

And even if the growing greenhouse effect melted nothing at all, the increased heat alone would raise the sea level considerably. Warm water takes up more space than cold water--this thermal expansion, given a global temperature increase of 1.5 to 4.5 degrees Celsius, should raise the seas a foot.

The immediate effects of this swollen sea would be seen in a place like the Maldive Islands. Most of this happy nation rises only 2 meters above the Indian Ocean. If the sea level were to rise 1 meter, storm surges would become an enormous, crippling danger; were it to rise 2 meters, a rise well within the range of possibilities predicted by many studies, the country would simply disappear.

Other nations, though not extinguished, would be horribly hurt. A two-meter rise in the sea level would flood 20% of the land in Bangladesh. In Egypt, such a rise would inundate only about 1% of the land, but that 1% includes much of the Nile delta, where most of the people live. All across Asia, farmers grow rice on low river deltas and flood plains. Because those farmers lack the resources to build dikes and seawalls (and in some places, such as Bangladesh, such defenses are practically impossible), harvests would almost certainly fall.

But it is not just the Third World that would suffer.

A couple of years ago, the United States Environmental Protection Agency issued a work sheet by which local governments could calculate their future position vis-a-vis the salt water. (In Sandy Hook, N.J., for instance, add 13 inches to account for local geological subsidence to the projected increase in sea level, for a net ocean rise of 4 feet 1 inch.) Direct inundation of land would cause a certain number of problems; in Massachusetts, for instance, between 3,000 and 10,000 acres of ocean-front land worth between $3 billion and $10 billion might disappear by 2025, and that figure that does not include land lost to growing ponds and bogs as the rising sea lifts the water table.

But storm surges would do the most dramatic damage. In Galveston, Texas, 98% of the land is within the plain that would be flooded by the worst storms.

There are other reasons, too, to fear a sea-level rise.

A few years ago, I spent a happy day with William Harkness, the rivermaster of the Delaware River. He has an office in Milford, Pa., and a little tower a few miles away on the river, right at a prime shad-fishing bend.

Essentially, his job is to watch the Delaware to see how much water flows past each day. If the flow drops below a certain level, he orders the City of New York, which maintains several great reservoirs on the upper reaches of the river, to release water downstream instead of piping it east to the city.

The rivermaster’s job results from several decades of litigation between New York City and the communities, especially Philadelphia, near the mouth of the Delaware. Under the agreement, New York must release enough water to keep the “salt front”--the ocean--from advancing up the river.

In normal times, the water pouring out of a river pushes the ocean back, but in a drought the reduced flow creates a vacuum, which the sea oozes in to fill. During the drought of the 1960s, said Harkness, the salt front nearly reached Philadelphia’s water intakes.

“It didn’t, but that’s something you worry about,” he said. “Everyone in Philly turning on a tap and getting salt water.”

The only problem with the present arrangement is that during a drought, when New York must release vast quantities of water down the Delaware to hold the salt front back, New Yorkers continue to take showers and wash their hands.

During the last severe Northeastern drought, in the summer of 1985, city officials made up for the diminished flow from the Delaware by pumping water straight from the Hudson. This worked well--the water turned out to be considerably cleaner than many had feared--but as the flow of the Hudson was reduced, the salt front began to creep up that river, and the town fathers of Poughkeepsie became very worried about their supply getting salty.

As the greenhouse warming kicks in, increased evaporation could steal 10%-24% of the water in New York’s reservoirs, the EPA concluded; in addition, a 1-meter sea-level rise could push the salt front up past the city’s water intakes on the Hudson. In all, says the government, “doubled carbon dioxide could produce a shortfall equal to 28%-42% of planned supply in the Hudson River Basin.”

The expected effects of a sea-level rise typify the many consequences of a global warming.

On the one hand, they are so big we literally can’t understand them. If there is a significant polar melting, the Earth’s center of gravity will shift, tipping the globe in such a way that the sea level might actually drop at Cape Horn and along the coast of Iceland--I read this in a recent EPA report and found that I didn’t really understand what it meant to tip the Earth, through I was awed by the idea.

On the other hand, the changes ultimately acquire a quite personal dimension: Should I put in a wall in front of my house? Does this taste salty to you? And, most telling of all, the human response to the problems, the utterly natural human attempt to preserve the old natural way of life in this post-natural world, creates entirely new consequences. The ocean rises; I build a wall; the marsh dies, and, with it, the fish.

What’s more, many of the various effects of the warming compound one another. If the weather grows hotter and I take more showers, more water must be diverted from the river, and the salt front moves upstream, and so on.

The contradictions multiply almost endlessly (more air conditioning means more power generated means more water sucked from the rivers to cool the generators means less water flowing downstream, et cetera ad infinitum).

These aren’t the simple complications of, say, last summer when the hot weather drove everyone on the East Coast to the beaches, only to discover the tide of syringes.

These contradictions are the result of throwing every single system into an uproar at the same time, so that none of nature’s reliable compensations can be counted on.

From “The End of Nature,” by Bill McKibben. Copyright, 1989, by William McKibben. Reprinted with the permission of Random House Inc. COMING UP

FRIDAY: How will the “greenhouse effect” affect the dinner table? As the planet heats up, the world’s food supply will become more and more uncertain.

SUNDAY: Can the consequences of the “greenhouse effect” be ameliorated? Unfortunately, there are no quick fixes.