Goodbye Doggerland

Climate changes, and even geological changes, can continue long after temperatures stop rising.

Cabins by the Lake

10,000 years ago the Black Sea was a freshwater lake. The ice age thousands of years before had frozen so much of the earth’s water into glaciers and arctic ice sheets that sea levels dropped dramatically. The shallower channel that connects the Black Sea to the Mediterranean—called the Bosphorus—became a dry valley. Then temperatures rose as the ice age waned, and sea levels started to rise too—but not evenly.

Inland bodies like the Black Sea were fed first by the melting glaciers, augmented by the higher rainfall of the warming atmosphere. Finally the Black Sea rose enough to breach the Bosophorus again. Now the freshwater lake drained into the lower saltwater Mediterranean. But all that flowing water carried sediment and eventually it built up into a silt dam that blocked the Bosophorus altogether.

The glaciers continued to retreat, but eventually they were so far from the Black Sea that their meltwater began to flow into rivers that emptied into the closer North Sea. Rivers into the Black Sea no longer brought enough water to keep up with evaporation. The level of the Black Sea began to fall even as the Mediterranean Sea had never stopped rising. By 9000 years ago the Mediterranean was higher than the Black Sea and only that silt dam held it back.

Two very different human modes of living thrived around the Black Sea at the time. Where millennia before big game hunters had stalked mammoths and reindeer across the tundra, now foraging bands with dogs and bows and arrows hunted deer and small game and gathered roots and berries in oak forests. Where those forests had been cleared a new people, farmers who generation by generation had migrated north from the Middle East, grew wheat and barley in the rich alluvial soils, and raised cattle and goats in the foothills. Both groups fished the freshwater lake with wicker traps, nets, and spears.

Suddenly 9000 years ago—or perhaps 7500 years ago according to some scientists—the silt dam gave way and the Bosphorus again became an open channel.

A cascade of salty water crashed with the force of two hundred Niagara Falls into the placid waters of the lake—and continued to do so for many months. The roar would have been heard 100 kilometers away—echoing in the ears of those hunting within the hills of Turkey and those who fished around the Mediterranean shores. Fifty cubic kilometres of water thundered into the lake each day until the Black Sea and the Mediterranean were one again… ¹

Scientists disagree whether there would have been high crashing waves like a disaster movie, a steady brackish flood, or something in between—maybe gradual rises with flash floods during rainstorms—but however it happened, lakeside woods, marshes, and those arable fields disappeared—an area nearly the size of Virginia fell below the waters. The peoples along the shores—those who didn’t die outright—were uprooted as radically as the refugees of war and genocide today.

The people of Doggerland might have considered their Black Sea neighbors lucky. Doggerland is what scientists call the former plain that once connected England, Denmark, Belgium, Holland, and Northern France.² This was an area larger than Virginia raised above the ocean by the reduced sea levels of the ice age. By 10,000 years ago with the world warming and sea levels rising a tidal basin had formed in the center. By 9000 years ago melting arctic ice and glacial runoff from what is now Britain was supplemented by that runoff redirected from glaciers that had once fed the Black Sea. The tidal basin became a deep inlet. Then about 8200 years ago a tsunami caused by a landslide in Norway seems to have rolled over the entire plain, covering thousands of miles in a day—an event truly reminiscent of disaster movies.³ The waters then may have receeded enough for a brackish, marshland to reappear, we don’t know, but sea levels were still rising, so by 7500 years ago—if not before—all that was left of Doggerland was an island, and by 7000 years ago that too was gone. Neolithic farmers don’t seem to have reached Doggerland by the time of its destruction, but Mesolithic human-and-dog groups of Doggerland like those of the Black Sea region had fished the streams and hunted the same woodlands and plains where their ice age ancestors had hunted big game. Now all were gone.

The sloshing goes on even after the bucket stops swinging.

Both of the geological cataclysms I described above happened because of rising temperatures. That much is certain, but both of these staggering ecological changes happened a thousand years after temperatures had stopped rising—had in fact stabilized at modern levels. The temperature, after a period spikes and plunges, found a stasis that has continued into our own time, but the ecological zones and geological form of the modern world didn’t stablize until long after the temperature stablized, because once certain climate processes begin they became self-perpetuating.

This fact is why so much of contemporary discourse on global warming is functionally insane. The planetary warming humans began through widespread fossil fuel use is now self-perpetuating. It will absolutely continue even if we stopped widespread fossil fuel use today. That red line was crossed in our lifetime (At least in mine). Forty years ago during the Arab Oil Embargo if the U.S. had stopped fossil fuel use things could have been different. (I’m not arguing the U.S. could have done this; that’s a discussion for another time.) Instead the U.S. doubled down on the fossil fuel economy. Twenty years ago after the 2008 economic meltdown could Obama have taken us in a different direction and would it have made a difference? Probably not, but maybe. What we can say for certain is it’s too late now. Innumerable feedback loops are already in play that can’t be stopped, and can barely be altered.⁴

Understand that the exposure of polar ice sheets to warming waters, warming air, and increased rainfall causes portions to sheer off, which exposes new portions of polar ice to warming waters, warming air, and increased rainfall. The same is true for glaciers. Rain, wind, and evaporation melt a layer of the glacier exposing the next layer. If the climate was warm enough to melt one layer it will be warm enough to melt the next and the next. Once melting starts it keeps going.

Likewise, the thawing of tundra releases methane that further increases the atmosphere’s temperature—faster than carbon dioxide.⁵ This thaws more tundra and so on.

We can take up the various tech bro fantasies of geoengineering at a future time, but for now realize that all of these notions contain the same arrogance and impracticality that got us into this mess to begin with. We’re not going to terraform Mars, we’re not going to geoengineer the atmosphere, we’re not going to stop global warming.

It’s too late. It’s meltwater under the bridge.

Good News Bad News

Bad News. So that’s a bit of bad news, isn’t it? Climate will continue to change even if the temperatures that started it stop rising, and temperatures will continue to rise, even if we stopped fossil fuel use today, and we can’t stop using fossil fuels today. No modern nation has anything close to the political organization, scientific understanding, economic system, or organizational ability to stop fossil fuel use. So although it’s caused by fossil fuel use rather than shifts in the earth’s tilt, at this point our global warming is just as inexorable as the global warming after the last ice age.

Good News. On the other hand one bit of good news is that worse-case projections for our current warming are much less radical than what previous humans have gone through. By 2100 we can expect temperatures on the planet to increase by something like 3-6°C over what will have been three hundred years. That’s a lot. However, humans in the Northern Hemisphere about 14,700 years ago (after the last ice age) had to contend with temperatures that rose by as much as 9-10°C in only fifty years. Then temperatures fell and remained low for several thousand years, but then about 11,600 years ago they spiked again by as much as 9-10°C in only fifty years.

More Good News. Another bit of good news is humans did not die out during these ecological changes. In fact, in many ways we came out the far end better than we went in.

Still More Good News. One claim sometimes made is that global warming will kill all life on the planet. This too is wrong. Even the most extreme projections for temperature increase would not make the earth as hot as it has been in previous periods, such as during the “Age of the Dinosaurs.”

Really Bad News. Unfortunately, the fact that the most recent really hot period is called the “Age of the Dinosaurs” and not the “Age of the Mammals” should clue us in that we’re in for a rocky ride. Even small changes during the last ten thousand years when temperatures have been remarkably stable can produce major effects. Historians debate the impact of a period called the “Little Ice Age” where there were massive famines, brutal wars, and lots of scapegoating, and that was only a change of .5°C. We’re looking at 3-6°C. Better than the 9-10°C roller coaster of the Bølling–Allerød or the early Holocene, but much worse than the Little Ice Age. Our world is built on climate expectations that will be increasingly untenable. The flooding that will damage and destroy so many coastal areas over the next century will not be on the scale of the flooding that destroyed Doggerland, or that as in the Black Sea our freshwater lakes will soon become saltwater seas, but the flooding will be—has already been—bad enough (See North Carolina). We can expect more fires like those in Canada a summer ago and Los Angeles earlier this year. We can expect changes in rainfall and ocean currents. It’s going to be very hard on mist people.

Good News. One final bit of good news is we’re not going into this blind. Our genus Homo has lived through the coming and going of many ice ages, and our own species, Homo sapiens, has survived a few, but while those groups had no concrete knowledge of what had happened before, the period since the most recent ice age is recent enough that we have abundent archaeological and geological evidence about what happened and how humans coped with it.

Wisdom is not about predicting the future like a gambler betting on the correcting roulette number. Wisdom is about preparing for a variety of possible futures, and the experiences of humans who came before us are invaluable to understanding what can happen and what that means for us.

What’s Next

Since January I’ve been trying to share some of what is known about the last 20,000 years in the Northern Hemisphere when the temperature graph was bouncing like an EKG and the climate was shifting as radically generation after generation as technological changes have shifted in more recent centuries. It’s challenging material because it’s so different from the more common knowledge of later periods, like Dynastic Egypt or the city-states of the Fertile Crescent.

You can review the pieces here:

Part I. Part II. Part III. Part IV.

Thanks for reading. Next we’ll be talking more about where and how farming began, and the origin of what many call “civilization.”

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1. P 153 Steven Mithen After the Ice

2. The name comes from the Dogger Bank, named after a sand bar in the North Sea, which was itself named after the Dutch fishing boats that trawled there. There were called doggers after a medieval Dutch word for cod.

3. The tsunami was presumably caused by something called the Storegga landslide in Norway. Though the water may have ebbed enough afterwards to expose land again until the theoretically bursting of North America’s Agassiz Lake would have raised sea levels enough to end Doggerland.

4. Even rising sea level is not a simple process of the water reaching a spot on immutable land. Ice sheets and glaciers literally weigh down the land, so their melting causes the land levels to rise too (Though less than the sea levels). Likewise, the increase in subsurface water—the “water table”—raises land as well. The drying out of an area as rainfall patterns change, literally drops the altitude of the land. (Think of how the drop in the water table in much of California is literally lowering the land.) Moreover, land changes don’t happen evenly, particularly with regard to the impact of glaciers. Think how if you sit on a couch it causes the edge of the cushion to rise slightly while the center sinks under your weight. In this way a glacier pushing down on the area it covers can raise the areas immediately around it. Another complex effect is that changes in air temperature alter levels of humidity which alters weight and density. Colder air tends to be drier; hotter air wetter. Heat rises but hot air is also wetter air and that makes it heavier. All of this affects wind patterns which influence erosion, and are influenced by geographic features like mountains. It’s all fascinating stuff, and very much beyond the hopes of the geoengineers.

5. Methane and other greenhouse gases increase atmospheric temperatures more than carbon dioxide but decay much more quickly than carbon dioxide, so their effects are much more temporary.