Twenty-First Century New York Forecast: Floods, Heat, Bugs

Even Noah would have been impressed.

For two days this week, New York City endured the lashings of one of the worst storms in recent history, a northeaster that flooded streets, downed power lines and dumped nearly eight inches of rain on Central Park. With its olive-sized raindrops, it had the feel of some Biblical melodrama, re-enacted for our environmental, if not spiritual, edification.

In Brooklyn, the Gowanus Canal topped its banks, sending cold, dark water pouring into apartments. In Queens, some residents were forced to paddle the streets in boats. Every borough had its stories, and with them came the nagging suspicion that some god of global warming had finally spoken.

Michael Oppenheimer, a geosciences professor at Princeton University and a leading thinker on climate change, saw the storm as a clear portent.

“You can really never tie one particular event directly to global warming in a cause-and-effect sense,” he said. “On the other hand, this is exactly the type of event that we’d expect to see more of in the future—this kind of gully-washing, incredibly intense downpour.”

“The storm was kind of a preview of things to come,” he concluded.

Though this preview might have been enough to scare a skeptic, it may not have been necessary: Even before the deluge, global warming had become a hot local topic, as if some invisible, earth-friendly virus had struck, simultaneously, the cerebella of movie stars, millionaires, average citizens and Michael Bloomberg.

This Sunday, Earth Day, the Mayor will announce the details of his 2030 sustainability plan—the 10-goal effort he outlined in December to prepare the city for its bigger, braver, environmentally challenged future. The plan’s goals include everything from reducing global-warming emissions by more than 30 percent to cleaning up all the contaminated land in the city.

According to a source close to the Mayor’s office, the plan will include steps toward both “mitigation” and “adaptation”—that is, reducing greenhouse-gas emissions that cause a rise in air temperatures and taking steps to deal with the inevitable consequences of them.

But however ambitious the plan, there will certainly be bureaucratic and financial challenges. It may not go far enough. Or the city may simply have gone past the point of no return. All of this would mean that New York is facing a wet, hot, stormy future.

“We think climate change is going to threaten New Yorkers’ health and wealth through a cocktail of higher temperatures, higher seas and possibly changes in precipitation patterns,” said Radley Horton, a climatologist with Columbia University’s Center for Climate Systems Research. “Those are the three main variables.”

Dr. Horton and his colleagues have been studying the fate of a climate-changed New York for about seven years, pouring over elaborate climate models in the West 112th Street building that once housed John Dewey and now sits above Tom’s Restaurant (of Seinfeld fame). Their predictions paint a milder future for New York than for many developing parts of the world, like South Africa, which is expected to endure serious droughts, or parts of Bangladesh, which will quite simply be submerged. But even so, while day-to-day city life might go on with little added drama, the extreme events—the heat waves, the droughts, the northeasters—are expected to become both more intense and more frequent.

“The analogy I like to use is that it’s sort of loaded dice,” said Dr. Horton. “You always have the dice roll, which is the natural variability, which is always present—but climate change loads the dice.”

A Rising Tide

By most accounts, the climate-change scenario that scientists fear most—the one that really loads the city’s dice—is a sea-level rise. As global warming heats the earth, the waters of the seas and oceans expand, elevating water levels across the planet. In New York, this means that by 2020—just 13 years from now—rising sea levels will have raised the waters around the city by three to four inches; by 2050, the waters will have crept up a total of eight to 10 inches; by 2080, 14 to 19 inches.

Those numbers may be conservative, because they ignore the whole troubling and uncertain issue of the polar ice caps.

And it gets creepier. Part of the rise in water levels will be due to the fact that New York is actually sinking—sinking—on the order of five to six inches a century as the result of subsidence (a complex dynamic related to this region’s recovery from the last ice age) and various other geologic goings-on. The result is that, with or without the ice caps, the city’s sea level is expected by scientists like Dr. Horton to climb one and a half to two feet by 2080.

If that happens, marshlands, beaches and the 14 sewage-treatment facilities that currently lie at the water’s edge could find themselves under water or seriously compromised.

In many ways, however, full-on inundation will pose only a minimal threat to the city—at least until the ice caps melt, should that happen. For most of New York, the real problem will be storm surge, the swollen crests of waves that could flood the boroughs if a powerful northeaster—or, as the seas rise, even a not-so-powerful one—struck the city.

Battery Park City is particularly vulnerable in such a scenario. So too are the financial district, the F.D.R. Drive, the Rockaways, Coney Island, certain subway lines, and a host of other neighborhoods and transportation hubs that lie low and close to the coast. These are areas that already flood from time to time, and a sea-level rise simply ups the ante.

According to the latest models, New York neighborhoods that currently flood every 100 or so years—victims of what is known as the 100-year storm, in climatologist-speak—can expect to experience this kind of dousing as frequently as every four years by 2080, in a worst-case scenario.

Wet, But Also Hot

Still, bad as the floods may be, they’re really only part of the global-warming story. Afterward, New York will get heat: the kind of intense, smoggy swelter that will sap energy, strain the power grid and wreak unimaginable havoc on certain types of female hair. It will also kill people.

Already, over the past century, climate change has pushed the city’s average annual temperatures up nearly two degrees Fah
renheit, while a deceptively bland-sounding phenomenon known as the “urban heat-island effect”—a heat-trapping effect that turns cities like New York into giant hot-air bubbles—has boosted it another degree. Along the way, winters have become warmer and the number of 90-degree scorchers has doubled from roughly seven to 14 days a summer—a trend, scientists say, that does not bode well for the future.

“I’m seriously concerned about it,” said Stuart Gaffin, one of Mr. Horton’s colleagues at the Center for Climate Systems Research and an expert on the urban heat-island effect. “I think it’s going to be one of the more problematic impacts we’re going to have.”

Dr. Gaffin and his fellow Columbia scientists have spent the last few years studying this “problematic impact.” Working off a mix of weather models and fieldwork, they have calculated that by 2020, New York temperatures will have climbed roughly two degrees; by 2050, they will have jumped between three and five degrees; and by 2080, the city’s average daily temperature will have leaped a hefty four to seven degrees, making New York feel more like today’s Virginia or North Carolina.

Ecosystems could unravel as native flora and fauna disappear, and thanks to the shorter frost periods, mosquito-born illnesses like malaria could once again rear their parasitic heads.

Then, come summer, New Yorkers can look forward to the kind of serious, body-wilting heat waves that could turn the whole summer into one long dog-day afternoon. By 2090, according to Dr. Gaffin, 90-degree days could be the norm, while as many as 30 days could top 95 degrees.

This is serious business. When heat waves strike, people die, as last summer’s 10-day, 140-death hot spell made clear. Elderly and poor New Yorkers will be the most likely victims, while asthma-sufferers will face all kinds of risks from the higher levels of pollution and ozone. Air conditioners will help, but in 2080—or heck, even 2007—it’s not entirely certain that the city’s aging power grid will be up to the presumably increased strain.

Drought is also a big concern among climate scientists—as, paradoxically, is flooding. Though precipitation is, for the most part, too tricky a phenomenon to predict in any precise, down-to-the-decimal fashion, quite a few models have begun to point toward a trend of droughts punctuated by intense, flood-causing storms—a mixture that could make water supply difficult to manage.

“It’s this idea that the extreme events are what are going to be affected the most,” explained Dr. Horton.

None of this is very pleasant to contemplate. While it certainly beats famine, land loss and some of the other afflictions that poorer nations can expect to face, it’s unnerving whenever you glimpse it—in a climate model, a storm or simply a park.

On a recent chill-nipped Friday, Michael Feller, the chief naturalist for the Parks Department’s Natural Resource Group, hovered at the edge of the Inwood Hill Park salt marsh, shouting into the wind.

“I’d say 90 percent of the marsh that was here is gone in the last 20 years,” he said, scanning the lonely stretch of mud and gulls.

Mr. Feller, a small, compact man, has worked at the Parks Department for nearly 25 years and has been studying the marsh—one of only two wetlands left in Manhattan—for almost as long. Back in the 1980’s, when he was just starting out, the park’s wetlands extended nearly 100 feet, filling the paisley-shaped Spuyten Duyvil lagoon with thick grass. But now, some 20 years later, Inwood’s wetlands have been reduced to little more than a sorry-looking rim of thatch.

The reasons for their retreat are complicated, a mix of known and unknown forces, but the rising sea level is almost certainly a culprit. And if the world’s globally warmed waters continue to rise, as the scientists predict, the city’s wetlands will quite likely continue their sad crawl toward obliteration.

This worries Mr. Feller. Wetlands are exquisitely rich, if pungent, ecosystems—spawning grounds for fish, habitats for birds and storage bins for storm water. As they continue to shrink, Mr. Feller fears that we are not only witnessing a tragedy in action, but a “metaphor” for tragedies to come.

“It’s really the prospect of the unraveling of many things as we know them,” he said. “I don’t think we’re going to know until it happens. But the point of no return is actually way before the actual event.” Twenty-First Century New York Forecast: Floods, Heat, Bugs