Deep Future: The Next 100,000 Years of Life on Earth - Hardcover

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Stopping the Ice

One can only hope that the expected extremes of the Anthropocene will not lead to conditions that cross the threshold to glaciation.
—Frank Sirocko, paleoclimatologist.


Shockingly long-term climatic changes await us as a result of modern human activity, but examining our effects on the deep future also raises a related question that is well worth considering: what would global climates have been like if we had left our fossil fuels in the ground rather than burning them?
In that alternative reality our descendants would still fret about climate, sea levels, and ice caps but the news would read quite differently from that of today. “There’s a massive, destructive climatic change coming, but scientists say that we can stop it if we take appropriate action now. If we go about business as usual, coastal settlements will be destroyed by sea-level shifts and entire nations will be covered with water. Frozen water. But there’s still hope. If we simply burn enough fossil fuels, we’ll warm the atmosphere enough to delay that icy disaster for thousands of years.”
I’m talking about the next ice age. When a paleoecologist like myself thinks about global climate change the exercise is as likely to involve visions of ice-sheet invasions as it is to include greenhouse warming. We still don’t know exactly why continent-sized glaciations come and go as they do, but they clearly have a rhythmic quality to them. Natural cyclic pulses take the long line of temperature history and snap it like a whip, looping it into a series of steep coolings and warmings. When viewed from a long-term perspective, major warmings of the past 2 to 3 million years can seem like brief thermal respites when the world came up for air between long icy dives; that’s why we call them “interglacials” rather than something that sounds more normal or permanent. The cyclic pattern also suggests that more ice ages await us in the future, so strongly in fact that climate scientists routinely refer to our own postglacial warm phase that we live in today as “the present interglacial.” Because of this admittedly unusual perspective, many of the paleoecologists I know balance their concerns about modern climate change with “yes, but it could also be a lot worse.”
Although such views are rare outside of narrow academic circles, I believe that they belong in the mainstream. Time perspectives long enough to include ice age prevention are not just the stuff of mind games but potentially important aspects of rational planning for our climatic future. In order to appreciate why this is so, however, it helps to look more deeply than usual into the nature of ice ages.
The last one began about 117,000 years ago and ended 11,700 years ago. During that long and terrible reign of cold, roughly a fifth of the world’s land surface resembled the icy interiors of Greenland and Antarctica today, especially in the higher northern latitudes. Most of what is now Canada and northern Europe was smothered under immense sheets of slowly creeping ice up to 2 miles (3 km) thick. The sites of today’s Chicago, Boston, and New York were obliterated, and what we now call Long Island is a plowed-up bow wave of detritus that marks the southern limit of the last major ice advance. Entire landscapes sagged under that tremendous weight, pressing down hundreds or even thousands of feet into the planet’s softer innards, and the gritty underbelly of the ice gouged deep scratches and grooves into solid bedrock that still scar the formerly glaciated regions of the world.
When you see glacial deposits and ice-scoured rock formations along a northerly roadside or trail, it’s easy to let your imagination strip away the towns and trees and crush your surroundings under great, grinding slabs of ice. I envision it quite often near my home in the Adirondack Mountains of upstate New York. Recently I was reminded of the frozen past when I stepped off a woodland path near Saint Regis Mountain to take a closer look at one of the largest glacial erratic boulders I’ve ever seen.
The massive chunk of gray anorthosite was broader and taller than my house, and the prying fingers of winter frost had plucked garage-sized flakes away from its lichen-crusted flanks. They lay in low heaps around the central body of rock like cast-off clothing. The base of the giant perched just high enough above the ground to leave shadowed crawl spaces below that made me think of of crouching hermits and cave bears. Peering into one of them I scanned its dusky floor for signs of residents but saw only earth-colored gravel. Clean, well-sorted, smoothly rounded gravel, just like the stuff in the shallow streambed nearby. Gravel that was never buried under forest soils or leaf litter and that still looked as fresh as it did when melting ice dropped this gigantic sheltering rock on top of it.
That primeval scene drew my imagination back to when these mountains were still emerging from their long, lightless imprisonment. The rustling beech, maples, and birches before me faded away, along with the duff and dirt beneath them, exposing a desolate brown wasteland of wet sand and pebbles that glistened under a cold clear sky. Not a tree in sight, not a shrub or flower, not even many lichens on the virgin boulders yet. Cloudy silt-laden streams and molten blue pools sparkled in the low spots, and remnant hill-sized blocks of decomposing ice hunkered down in the deeper hollows, sloughing off layers of dusty surface debris like old dogs shedding winter fur. Far off on the northern horizon lay an unfamiliar range of white, mile-high hills, the sun-scored southern face of the melting ice sheet. The vision lasted only a few moments, but a strong feeling of connection to long-ago times when Big Ice ruled this landscape stayed with me through the rest of my hike that day.
The author examining a glacial boulder near Saint Regis Mountain in the Adirondack Park, upstate New York. Kary Johnson
Let’s continue with this imagination game. What if it happened again?
Here and now in the Adirondacks we worry, with good reason, about the effects of acid rain, invasive species, and global warming on our local ecosystems. But those problems won’t exterminate every last Adirondack fish and fowl, and even the most extreme case of Anthropocene heating would still leave the land covered with some sort of greenery, if not all the kinds we’re currently used to.
A full glacial advance, on the other hand, is a total wipeout. Every lake is bulldozed or smothered under a thick blanket of cobbles, sand, and gravel. Every sugar maple, every golden-tinted trout lily, every tuft of moss heaves up in bow waves of dirt and stones and is crushed to pulp. Every animal with legs or wings flees southward. The Adirondack peaks vanish under a heavy white tide, the iconic ski jumps at Lake Placid topple and are ground to splinters, and every settlement from Saranac Lake to Old Forge is obliterated.
Meanwhile, farther north, most of Canada disappears. That includes Quebec City, Montreal, Ottawa, Toronto, Winnipeg, Calgary, and Vancouver, not to mention every wild area from Hudson Bay to Banff. From a human perspective, there’s no place called Canada for tens of thousands of years except in the same sense that a gigantic frosty slab called Antarctica now squats on the South Pole. And out across the Atlantic, advancing walls of white demolish Dublin, Liverpool, Oslo, Stockholm, Copenhagen, Helsinki, and Saint Petersburg, and every settlement on the rocky coastal rind of Greenland is shoveled into the sea by heavy spatulas of ice.
With much of the world’s freshwater imprisoned in frozen form on the continents, sea level falls by as much as 400 vertical feet...