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I’ve been having a lot of fun reading Curt Stager’s book Deep Future: The Next 100,000 Years of Life on Earth, (Amazon Link), and I highly recommend it, especially for anyone interested in science fiction. I linked Dr. Stager’s webpage to his name up there, but for anyone who doesn’t want to follow the link, he’s a PhD paleoecologist, as well as a science writer. In other words, he knows what he’s talking about.
The reason for highlighting his book here is what he lays out for the future of atmospheric carbon on this planet. I think the people who glance at this blog get the idea that I’m not a typical science fiction geek. I’m getting increasingly less fond of the miracle fix, which in this case would be something like fusion (“safe,” “cheap” energy), plus a miraculous gadget to turn CO2 back into a coal that doesn’t involve burying a swamp under rock for a few dozen million years. Also, I’m a SFF maverick who doesn’t really believe that humans will a) go extinct in the near future, or b) transcend through some singularity to the point we are no longer human. That was me ten years ago. Now? Not so much.
The question is, what does the next 100,000 years hold in store for us? Oddly enough, it does depend on how much carbon we burn in the next century or so, whether we go for the conservative 1000 gigaton release of CO2, or the “use up all the coal and to hell with it” 5000 gigaton release of CO2. These are the “moderate” and “extreme” scenarios used by the International Panel on Climate Change, incidentally. To put it into perspective, we’ve released something like 300 gigtons of CO2 since the start of the Industrial Revolution, so the IPCC’s idea of moderation is pretty grimly realistic, compared with the 350 ppm goals of climate activists (the idea is that 1000 gigatons is what we get when we try for 350 ppm and miss).
The good news: If one follows the Milankovitch cycles, the next probable ice age would have been around 50,000 years from now, assuming atmospheric [CO2] was no higher than 250 ppm. Under both the moderate and extreme gas release scenarios, atmospheric CO2 will be above 250 ppm, so we can breathe easy, there won’t be an ice age in 50,000 years. Compared with global warming, an ice age is a serious problem.
The bad news: the carbon will take a very long time to leave our atmosphere. Most of it will go into acidifying our rocks and oceans, but fortunately we’ve got a lot of calcium bicarbonate lying around in the ocean (and in limestone on land) to help sequester about 750 gigatons of carbon. This will take a while, and since much of the soluble calcium occurs in things like coral reefs and mollusk shells, we’re going to mess up the oceans. A lot.
Under the moderate scenario, mean temperatures peak a few degrees higher than they are now, and average sea levels 6 to 7 meters higher than they are now, and these maxima will occur perhaps a century after we reach peak carbon concentrations. The reason for the lag is that the oceans will take a long time to respond, because they are so very large.
As we’re finding out, though, the averages don’t tell the story. Some climate scientists prefer “global weirding” to “global warming,” and class the unusual weather we’re having under climate change. And we’ve only experienced about a degree of average temperature increase so far. I’m not sure what saying that global weather will get four times weirder means in real terms, but it probably won’t be pleasant for most people.
The interesting part is how the carbon leaves the atmosphere. Under the moderate scenario, the limestone scrubbers will take about 7000 years to get their 750 gigatons of carbon out. At that point, silicate minerals (granite, basalt, etc) take over. Over the next 50,000 years, they will get [CO2] down to where it is today, and it will probably take them another 100,000 years to get it down to baseline. There’s another Milankovitch-induced ice age lurking out around 130,000 years in the future, and it’s possible that one will happen, if we stick to our moderate carbon release scenario (or rather, if do everything we can to get off fossil fuels now, and fail).
Then there’s the extreme scenario, 5000 gigatons of carbon, all of our oil and coal up in smoke. Temperatures would peak somewhere between 2500 and 3500 AD, at 5 to 9 degrees C above today’s mean temperatures (read weather 5 to 10 times more weird than we have today). Sea level rises up around 80 meters over the next few millennia, with most of that (not all of it) in the first thousand years (that’s right, continual sea level rise for centuries). Ultimately, it takes over 100,000 years for the rocks to sequester carbon to today’s level (and for the sea to drop back 80 meters), and 400,000-500,000 years for a full recovery.
In the moderate scenario, most of the changes take place in the first 1000 years, followed by a long, slow rebound, while in the extreme scenario, the heat and water keep rising for thousands of years, followed by an enormous, even slower rebound.
In both cases, though, the Earth will eventually equilibrate, the carbon will get scrubbed out of the air, and humans will face another ice age. If people are smart today and don’t use up all the coal, our distant descendents may decide to burp another gigaton of CO2 into the air 130,000 years from now, to prevent the next ice age. If we’ve burned through it all, too bad, they’re screwed, and all the polar high civilizations they’ve developed will be ground into forgotten dust by the resurgent glaciers. Since the Earth will have gone through an Eocene-style global hothouse, there won’t, of course, be any polar species left to take advantage of the advancing ice, so the next ice age might be a rather barren place, unlike the last one. But heck, when have any extremists worried about the distant future?
The other fun part of this scenario is how we’re going to live during the coming hot times, which is the ultimate reason I’m blogging here. One technology I’d like to focus on is biodiesel, Craig Venter style. In a recent Wired interview, Dr. Venter talked about the great idea of using algae to make diesel or gasoline. The algae would make diesel precursors, rather than the starches or oils they store now. Nothing too farfetched here, there are companies working on the same idea now, using unicellular marine algae. In the future, it’s quite likely we’ll see huge algae farms springing up in deserts and along desert seascoasts all over the world, where they make diesel using algae and saltwater. It uses non-potable water and barren land. What’s not to like?
The fun part that Dr. Venter didn’t talk about is the carbon cycle. The algae scheme only works if there’s a lot of CO2 in the air. The CO2 will get fixed into fuel by the algae, then burned off to power motors. This isn’t as stupid as it sounds, because diesel and gasoline really are great energy sources. The only limitation will be the amount of sun each algae farm gets. In general, the future gas industry will be solar powered, and there will be rich investors who want to keep a lot of carbon in the air. They may not want to deal with continually increasing sea levels and progressively radically unpredictable weather, but we’ll have to wait and see whether such predictions make them wiser, or not. Regardless, this will be a limited solar age, using gas as a storage medium, not the cheap, plentiful fossil gas we have even now.
Ultimately though, unless people do something drastic about limiting weathering, all that atmospheric carbon will disappear, and the hydrocarbon age will end. This end might happen even faster, if farmers try to sequester carbon into their trees or into their soil (soil carbon helps soils hold nutrients). Personally, I foresee a continual conflict between the fuel industry, on the one hand, who wants to keep CO2 in the air for recycling as long as possible, and nature and farmers on the other hand, who want to sequester carbon in the soil and the rock. A war between air and darkness, as it were? In the end, the world will sequester all the surplus atmospheric CO2 into forms we can’t burn, and if we haven’t weaned ourselves off gas by then, we will be ultimately screwed. Of course, if we have gone post hydrocarbon, humans will be dealing with another ice age.
This gives SFF writers a lot of future to play in, does it not? Anyone want to try playing with it?
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