The World Without Us

Even if the Statue of Liberty ends up at the bottom of the harbor, Appelbaum says, its form will remain intact indefinitely, albeit somewhat chemically altered and possibly encased in barnacles. That might be the safest place for it, because at some point thousands of years hence, any stone walls still standing—maybe chunks of St. Paul’s Chapel across from the World Trade Center, built in 1766 from Manhattan’s own hard schist—must finally fall. Three times in the past 100,000 years, glaciers have scraped New York clean. Unless humankind’s Faustian affair with carbon fuels ends up tipping the atmosphere past the point of no return, and runaway global warming transfigures Earth into Venus, at some unknown date glaciers will do so again. The mature beech-oak-ash-ailanthus forest will be mowed down. The four giant mounds of entombed garbage at the Fresh Kills landfill on Staten Island will be flattened, their vast accumulation of stubborn PVC plastic and of one of the most durable human creations of all—glass—ground to powder.

After the ice recedes, buried in the moraine and eventually in geologic layers below will be an unnatural concentration of a reddish metal, which briefly had assumed the form of wiring and plumbing. Then it was hauled to the dump and returned to the Earth. The next toolmaker to arrive or evolve on this planet might discover and use it, but by then there would be nothing to indicate that it was us who put it there.

CHAPTER 4 The World Just Before Us

1. An Interglacial Interlude

FOR MORE THAN 1 billion years, sheets of ice have been sliding back and forth from the poles, sometimes actually meeting at the equator. The reasons involve continental drift, the Earth’s mildly eccentric orbit, its wobbly axis, and swings in atmospheric carbon dioxide. For the last few million years, with the continents basically where we find them today, ice ages have recurred fairly regularly and lasted upwards of 100,000 years, with intervening thaws averaging 12,000 to 28,000 years.

The last glacier left New York 11,000 years ago. Under normal conditions, the next to flatten Manhattan would be due any day now, though there’s growing doubt that it will arrive on schedule. Many scientists now guess that the current intermission before the next frigid act will last a lot longer, because we’ve managed to postpone the inevitable by stuffing our atmospheric quilt with extra insulation. Comparisons to ancient bubbles in Antarctic ice cores reveal there’s more CO₂ floating around today than at any time in the past 650,000 years. If people cease to exist tomorrow and we never send another carbon-bearing molecule skyward, what we’ve already set in motion must still play itself out.

That won’t happen quickly by our standards, although our standards are changing, because we Homo sapiens didn’t bother to wait until fossilization to enter geologic time. By becoming a veritable force of nature, we’ve already done so. Among the human-crafted artifacts that will last the longest after we’re gone is our redesigned atmosphere. Thus, Tyler Volk finds nothing strange about being an architect teaching atmospheric physics and marine chemistry on the New York University biology faculty. He finds he must draw on all those disciplines to describe how humans have turned the atmosphere, biosphere, and the briny deep into something that, until now, only volcanoes and colliding continental plates have been able to achieve.

Volk is a lanky man with wavy dark hair and eyes that scrunch into crescents when he ponders. Leaning back in his chair, he studies a poster that nearly fills his office bulletin board. It portrays atmosphere and oceans as a single fluid with layers of deepening density. Until about 200 years ago, carbon dioxide from the gaseous part above dissolved into the liquid part below at a steady rate that kept the world at equilibrium. Now, with atmospheric CO₂ levels so high, the ocean needs to readjust. But because it’s so big, he says, that takes time.

“Say there are no more people burning fuel. At first, the ocean’s surface will absorb CO₂ rapidly. As it saturates, that slows. It loses some CO₂ to photosynthesizing organisms. Slowly, as the seas mix, it sinks, and ancient, unsaturated water rises from the depths to replace it.”

It takes 1,000 years for the ocean to completely turn over, but that doesn’t bring the Earth back to pre-industrial purity. Ocean and atmosphere are more in balance with each other, but both are still supercharged with CO₂. So is the land, where excess carbon will cycle through soil and life-forms that absorb but eventually release it. So where can it go? “Normally,” says Volk, “the biosphere is like an upside-down glass jar: On top, it’s basically closed to any extra matter, except for letting in a few meteors. At the bottom, the lid is slightly open—to volcanoes.”