The luck of the Sapiens: the weird fortuitousness of global warming

The Arctic's long-term cooling, and then abrupt warming in 20th Cent.

In all the hullaballoo around global warming, there’s one oft-overlooked tidbit that warrants, at the very least, some philosophical contemplation. And that is the following: Were it not for all the fossil fuels we’ve burned, right about now we’d be headed into another Ice Age.

For 2 million years or so, variations in Earth’s orbit — a wobble in earth’s rotational axis relative to its orbital plane — have ushered in periods of glaciation on roughly a 100,000-year frequency. One recent study in the journal Science found that the Arctic has been slowly cooling for two millennia, advancing toward that “tipping point” beyond which glaciers begin their grinding, crushing sweep southward from the Arctic, but that the cooling abruptly reversed in the 20th Century.

That’s because, some 200 years ago, the Industrial Revolution began. Lots of coal, and then oil, went up in smoke. The rising concentrations of atmospheric CO2 increased the atmosphere’s ability to hold heat. Humanity has quite accidentally warded off another Ice Age — 50 millennia of advancing ice, followed by another 50 of de-icing. What strangely good luck.
It this point, I’ll insert a huge qualifier. The problems posed by global warming are gargantuan, and no laughing matter. Where will the 150 million inhabitants of already flood-prone Bangladesh go when sea levels rise? What about expanding subtropical deserts? How will polar bears, ringed seals and walruses fare as polar ice becomes increasingly scarce. How will earth’s web of life respond to an estimated loss of 20 to 30 percent of all living things? And — one of the most sobering aspects more atmospheric co2 — what will happen to marine ecosystems as the ocean becomes increasingly acidic?

Now that this caveat has been solidly planted in the mud, back to the strange good luck of it all — our accidentally increasing the planet’s greenhouse effect just as another ice age was scheduled to begin.

During the height of the last one about 20,000 years ago, ice sheets a mile thick in places covered much of the northern hemisphere. New York’s 118-mile long Long Island is the rubble that washed off of — and perhaps was pushed in front of — one of these glaciers. So are Nantucket and Cape Cod.

To this day, the upper midwest continues to rebound, free of the tremendous weight of all that ice. So does Scandinavia. By some estimates, Canada’s Hudson Bay has another 100 meters to rise before it will have fully recovered, meaning that this shallow sea, which averages around 100 meters in depth, may one day cease to exist entirely.

The point is, an Ice Age would seriously crimp our style. Everything, New York, London, and Moscow included, would have to shift toward the equator. Last time humanity faced large-scale global cooling about 80,000 years ago, we consisted of ragtag groups of hunter-gatherers. No problem adjusting then. We just did what the animals did and followed them.

This time, however, we’re not nomads. Much of North America and Europe would have to shift southward. And I have a hard time imagining subtropical nations welcoming hundreds of millions of refugees from higher latitude with open arms. (I can’t imagine the converse, either — the course we’re on: higher latitude nations welcoming refugees from lower latitudes.)

So here’s my wager: if somehow civilization had arrived at its current stage of development without burning fossil fuels, and if we were still at 280 parts per million and not the current 387 ppm, I bet that we’d be having a different discussion about climate right now. We’d be arguing over what greenhouse gases were safe to emit — the relative merits and dangers of methane versus CFCs or ozone, say — to keep things nice and warm.

One recent study made this point explicitly. Writing in the journal Geophysical Research Letters, these scientists argued that fossil fuels were so valuable as a source of climate-altering carbon that we should stop burning them now and save them for later when we really needed them. They calculated that by releasing pulses of co2 from fossil fuels at the right time, we could maintain the current balmy interglacial conditions for another 500,000 years.

In another study last year, scientists concluded that not only was earth headed into an Ice Age, the next Ice Age would likely be permanent. The cold-then-hot-and-then-cold-again cycles of the past 1 million years represented the flip-flopping of a complex system, earth’s climate, settling into a new steady state: permanent glaciation. In other words, there would be no warm interglacial after the next ice age.

Commenting on this study, NASA’s James Hansen wrote in to the NY Times’ Dot Earth blog, reminding everyone that global cooling isn’t the problem. “It would take only one CFC factory to avert any natural cooling tendency. Our problem is the opposite: we cannot seem to find a way to keep our GHG forcing at a level that assures a climate resembling that of the past 10,000 years,” he said.

And yet, I can’t help but marvel at the sheer fortuitousness of it all. We accidentally change climate right when our species has built something  — modern civilization — whose continued existence depends to a large degree on climate remaining the same — i.e. glaciers NOT advancing to cover one-third of earth’s surface

More on this seeming serendipity in some later post. But it strikes me that, in the long-term, the real question facing humanity isn’t just “How do we get back to 280 ppm?” It’s “How do we safely engineer climate to keep it where we like it?”

You might call the guiding principle “the Pottery Barn Rule for climate”: If you’ve broken your planet’s climate — or perhaps if you simply have the capacity to break your planet’s climate — and you’re aware that you’ve done so, then you’ve got to buy it. Which is a long way of saying that Homo sapiens now “owns” Earth’s climate.

By Moises Velasquez-Manoff

Graphic from study in Science on the Arctic’s long-term cooling trend, which reversed in the 20th Century.