Putting the life back in science fiction

Our Carbonated Future–the next 400,000 to one milion years
May 31, 2012, 9:56 pm
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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?


16 Comments so far
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A lot to think about here. I’m really not too concerned about the next ice age; the ice age cycle is so slow, compared to human technology change. The problem with CO2 is not the absolute level but the pace of change. The biosphere’s rate of evolution cannot adapt that fast.

Does the analysis you read include methane? Methane is a wild card. There could be enough escaping from the deep to turn us into Venus.

Comment by Joan S.

Hi Joan,

I can’t answer the question without spending a fair amount of money going into the primary literature. My take on methane is that it degrades in sunlight, so that, while it can cause a short term spike (being a more potent greenhouse gas), I’m not sure what happens long term. Presumably it adds to the CO2. I’m also not sure how much methane there is in permafrost and clathrates, and I’m not sure anyone really knows, either.

The Earth has been through apparent methane outgassings before, most recently in the Paleocene-Eocene Thermal Maximum, so I don’t think it’s a biosphere buster. It might accelerate the mass extinction, though.

While the pace of change is important (and I agree here), the models do say that the biggest effects lag by centuries after we hit maximum CO2 release. Since we respond better to crises than slow problems, this is, ironically, a big problem. For example, port cities will have to be rebuilt inland every few decades-centuries for centuries to come. That’s a messy proposition, because it gets political.

Comment by heteromeles

[…] great links on carbon and climate change: Methane seeps in the Arctic, and Our Carbonated Future from […]

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Does this book discuss nuclear material?

A book about the planet 100,000 years from now must not ignore the question of where all the nuclear waste has been, or has not been stored (ex: released in a meltdown,… or worse).

If we don’t solve the nuclear problem, there won’t be any life to worry about CO2… much sooner than 100k years from now. But radioactive isotopes from our times will still be in a process of decay by then.

Comment by TransAlchemy

I agree it’s an issue, but since the book is primarily about climate, he didn’t touch on nuclear wastes. My personal take is that life will survive, as witnessed by Chernobyl. Note that I’m not saying it will be untouched by nuclear contamination. Rather, I’m saying that currently nuclear reactors are a minor global problem, albeit a really long term problem, and life seems to tolerate a fair amount of contamination, albeit not without problems. Neither Chernobyl nor Bikini Atoll are lifeless (nor is the Fukushima area), although I wouldn’t want to spend time in any of them if I had a choice.

There are a couple of ironic issues with nuclear reactors. One the one hand, if we decide to get off carbon by getting serious about nuclear power (perhaps with thorium reactors or some such), we have bigger problems with nuclear waste, but we get the CO2 out of the atmosphere faster. This insures we run into another ice age 130,000 years from now, and then we have to worry about all the waste stockpiles getting ground down by glaciers, or mobilized if places like Nevada suddenly become wet again and water floods previously dry storage caverns..

If you’re strongly anti-nuclear, you may want to hope for a coming crash. The thing is, nuclear plants currently take a lot of fossil fuel to build (for moving things, processing fuel, piling on all that concrete, etc), and if we wait too long, fuel may get so expensive that we won’t be able to build another nuclear power plant. At that point, we’re stuck with renewable sources, whether they’re a workable solution or not.

Comment by heteromeles

Venter clearly does not see algal diesel as sufficient to replace all fossil oil consumption. You have complained about putting in solar power plants in desert areas (fresh water requirements) but I gave to wonder at the impact of large areas of algal farms in those same areas. Would we not be better off running these things in the open ocean?

Comment by alexandertolley

You’re right, that “what’s not to like” comment was ironic. Still, salty water is the bane of many arid agriculture areas, so if there’s a choice between a farm abandoned because it’s too salty, and an algae plant, the algae plant’s probably worth having. Replacing undisturbed desert with an algae plant is probably a bad idea.

As for coastal algal fuel plants, my understanding is they’re already planning or building them, in places like the Red Sea. Whether they’ll work is another matter, and given how coastal plants and animals tend to be unique and confined to coastal areas, the potential for environmental damage is quite high. Sea levels rising for another century or millennium is another problem that any coastal facility will have to deal with.

As for open ocean, I know there’s a big kick right now floating city-states, and I agree, there’s some appeal to it as a solution. The two big issues (as I see them) are surface area and contamination. I’ve worked with an algae scientist, and keeping the cultures free of contamination was always a major issue. Insuring your prized diesel algae is the only thing growing in your setup will always be a huge issue, and surrounding that setup with wild algae that live in saltwater is not a good way to keep the culture pure. As for surface area, this is basically another form of solar cell, and these work best when they cover a large area. I’m not sure how feasible this is on the ocean, especially during storms.

Still, there’s no reason for a SF writer not to write about it.

I’m comfortable with the bigger point, which is that (absent a technological revolution in batteries or power generation), industry will start pulling carbon out of the air, fixing into hydrocarbon-based fuels, and burning it back into the air. After all, the major problem with gasoline is a fuel is its environmental effects, not its engineering qualities. We might get there through algae or other biomass conversion, or we might get there through some sort of trash-to-diesel plant, but petroleum-type products are just too useful, and it’s not clear that we can substitute for everything they do (yes, the Romans undoubtedly said the same thing about lead, which is why we use plastic and copper pipes now instead of lead ones). The amount of fuel and feedstock produced this way will be substantially lower than what we’re hauling out of the ground at present, but I don’t think that’s going to stop industry from doing it.

For SF writers, there’s a couple of interesting points here. One is the lag times and the apparent inevitability of a return to present day conditions, followed eventually by another ice age. The question is when, not if, with the next ice age. The other is that if we look at aerial carbon dioxide as a feedstock for both the oil and agricultural industries, there’s political ecology here. This isn’t just about fiddling with Earth’s HVAC, there’s money to be made and lost here, and potential fights about how to use sunlight and carbon, set against a world with less energy to go around.

Comment by Heteromeles

I don’t think that algae farms and CO2 abatement efforts will ever be in serious competition. The process bottleneck for turning CO2 into fuel via solar energy (mediated by organisms or machines) is not going to be supplying CO2, whether the atmosphere is at 350 PPM or 700 PPM.

I think that after the real consequences of climate change become obvious there’s going to be a mad dash to reverse it, perhaps as fervent and well funded as the denial and delay tactics that currently prevent efforts to forestall it.


I’m not going to provide links for everything because it would take a long time to re-gather all my sources, but there are some relatively low tech efforts that can draw down atmospheric CO2. Note that they can draw down atmospheric CO2 in absolute terms only after anthropogenic emissions have been sharply curtailed; if we keep burning coal like we do today, or even faster, these mitigation efforts will only slightly retard the rate of atmospheric CO2 increase.

1. Biochar has the potential to sequester up to about 1.8 gigatonnes of CO2 annually. Biochar is simply waste plant matter that is heated with limited oxygen access, so it converts to charcoal-rich material. The char material is more kinetically stable to metabolism in soil than unaltered plant waste, so carbon can be locked up for centuries or longer. Note that the kinetics depend on particle size; fine char dust may be rapidly metabolized in soil, while walnut size char lumps may persist for thousands of years. Apart from locking up carbon, biochar soil amendments can also improve soil water retention, reduce nitrous oxide byproducts on fertilized land, improve plant nutrient uptake, and bind hydrophobic pollutants.

2. Amending acidic soils with finely ground magnesium and calcium silicates, particularly in the tropics, has the potential to sequester about 1 gigatonne of CO2 annually. Again this improves soil productivity at the same time it offsets carbon directly. It just accelerates the natural silicate weathering cycle.

3. Reforestation efforts have the potential to lock up perhaps another 8 gigatonnes of CO2 annually. The forests actually have to stay around or be turned into durable products, not paper or biofuels, in order to make an enduring contribution.


This is stuff that might make an interesting element of SF stories. It may be part of our real future too, but it’s more speculative.

1. Active afforestation efforts in the world’s large deserts. It seems that it may be possible to turn deserts into forests with large scale efforts to deliver water, build soils, and plant trees until the forest is large and hardy enough to make a self-sustaining climate pump. If you want to dream big, imagine the long effort to turn the Sahara into forest, starting at the west coast of north Africa and working eastward.

2. More aggressive efforts to accelerate silicate weathering. The most audacious approach I’ve ever seen is the 2007 paper “Electrochemical Acceleration of Chemical Weathering as an Energetically Feasible Approach to Mitigating Anthropogenic Climate Change.” It uses a lot of electricity to accelerate silicate weathering by several orders of magnitude and can attack just about any rock, though the best candidates are calcium and magnesium rich silicates.

A process with lower technical and energy intensity is proposed in the recent “Rolling stones; fast weathering of olivine in shallow seas for cost effective CO2 capture and mitigation of global warming and ocean acidification.” The proposal is to place crushed magnesium silicates or similar minerals in near-shore ocean areas so that the action of surf grinds the particles against each other and greatly accelerates silicate weathering without huge human effort. Crushing huge rocks to gravel and transporting them is relatively cheap in energy terms; it is reducing the rocks to dust that is energetically expensive, and in this proposal the sea does that work without more human-supplied energy or machinery. I suspect that even common basalt could be usefully employed this way, with somewhat slower kinetics, if there is insufficient olivine nearby.


1. Fossil fuel power plants with integrated carbon capture and storage. It’s expensive even on paper, it’s never been properly demonstrated, and the only time it seems to come up is when the coal industry wants to justify why it could theoretically, sometime far in the future, with enormous subsidies, become a responsible source of energy.

2. Giant mirrors, sulfate aerosols, and other mega-scale efforts to increase the Earth’s albedo. There’s a lot of uncertainty about side effects, costs would be high, and it does nothing to fix the atmospheric or oceanic CO2 concentrations.

3. Iron ocean fertilization. It seemed like a possible avenue at one time, but it appears that in field conditions you don’t get big enough blooms and the blooms don’t send much carbon to the deep ocean.

Comment by Matt

Thanks for the summary Matt. While I somewhat disagree about the levels of human use of CO2, I think we agree that the bottleneck is getting the energy (especially solar energy) to make into gasoline. This is another potential future, actually, for anyone thinking about deep future issues.

As for carbon sequestration, I love the summary, although I have some quibbles.
–biochar: I love the stuff, and anyone writing about a future small farm where they don’t have biochar-producing stoves is missing two major tech developments: efficient cookstove technology (which is a hot field in the development community) and biochar production. These two can go together, with efficient stoves producing biochar. My quibble is that I’m hearing rumbles that the soil scientists have less of a handle on soil carbon than they thought they did, and that includes the lifespan of biochar in the soil. I’m not going to complain about the big lumps of charcoal–they’re good for archeological time spans–but small bits may decay faster under some circumstances, and it’s not clear that it’s just size related.
–Soil amendments in the tropics? The idea for biochar came from terra preta in the Amazon, and it’s really low powered. Getting carbon into tropical soils gives them the nutrient holding capacity they need, and wastes can provide the nutrients themselves. Grinding and shipping rock is an industrial solution. We can do it now, but what a lower energy future? Barges of rock powder in going down the Amazon from the Andes? That sounds expensive.
–Reforestation: yep, and especially if you can get the wood into duff in the forest floor, or into buildings that stay around for centuries. Agroforestry (gardening with trees crops as well as annuals) is another great way to do this.

The issue with the science fictional approaches is that they all require a lot of energy to transport stuff, and energy shortages look to be an enduring problem in the future. Not a good combination. Additionally, the global climate models suggest that climatological deserts are going to spread as the Earth warms. Afforestation and revegetation can help keep manmade deserts from spreading (say on the southern edge of the Sahel, or in China), and this is a GOOD thing. But from here, it doesn’t look like turning the Sahara green will work until the Ice starts growing again.

As for the laughable distractions: right on, and thanks.

Comment by Heteromeles

Hi Heteromoles,

Thanks for the thoughtful responses. As for applying ground silicates to agricultural soil, the idea is that they would replace more conventional soil amendments like agricultural lime, so the overall energy consumption doesn’t go up much (both materials need mining, crushing, and transport) but the soil pH management also grabs some carbon as a side effect.

I know that I have a somewhat more optimistic view of future energy supplies than you do. I believe that we’re facing a liquid fuels crisis more than a general energy crisis, but it’s compounded by the threat of global warming. In the early 1970s “use lots of coal” looked like a reasonable response to the drastic oil price rise; not so much today.

I think that in the near future wind and solar power will be cheaper in many places than the grid delivered output from a state of the art coal plant. There are already regions where renewable electricity is cheaper than the retail prices from incumbent fossil fuel generators. India, Kenya, Malaysia, Indonesia, Egypt… they and many other less developed nations are investing in renewable energy not because they are playing sleight-of-hand with government money, or because Greenpeace is bossing them around, but because it makes sense on environmental, economic, and security grounds. But renewable energy is most affordable if you can use it immediately, without storage, and nearby, without long distance transmission.

Possible audacious future projects like accelerated weathering of vast ultramafic bodies are pretty good fits to intermittent renewables. As long as your long term average progress is predictable it doesn’t really matter whether the work is fastest at noon on Wednesday or 2:00 AM on Saturday. Instead of doing a lot of transport, identify appropriate mineral deposits near the coasts and build the generating equipment there along with the processing equipment.

Comment by Matt

Wee! There are a couple of little issues here.
One is that I’m learning that wind turbines near houses aren’t exactly pleasant, at least with current designs. The problems include aircraft-level noise (>80 decibels a few hundred feet away), constant flickering (especially if the sun sets behind the turbine–apparently it’s really annoying), the possibility of fire (if the turbine transmission blows) and/or turbine “jump.” In the last, if the blades stop suddenly, perhaps because one flexes so much in the wind that it hits a guide wire or the pylon, then the whole giant propeller jumps off and goes somewhere, probably in a few large pieces. Considering that, where I live, a turbine 80′ tall with 40′ blades is considered “small,” I’m rapidly coming to the conclusion that we don’t want these things near houses.

The good news is that designs are changing so fast that we may find safer, more liveable wind generators. Still, they seem to work best when they’re large, and there’s a lot of energy involved. When something large that contains a lot of kinetic energy breaks, it’s going to be dangerous in some degree.

Solar has its own issues. While I like the idea of paving roofs with solar panels, that puts cities in the interesting place of coordinating among a lot of different homeowners to collectively power the city. Given how people feel about owning their homes (at least in the US), the idea that their roof partly belongs to their city is going to cause political problems. Still, some cities are experimenting with it, and we’ll see how it works out. Perhaps it will bring people together in empowered community building.

As for building on ultramafic deposits near the ocean, that has some serious problems. Aside from the small issue that ultramafics tend to be hotspots for rare plants, they have two other issues. One is that they often support mines (ultramafic means high in iron and/or magnesium, and can have everything from soapstone to jade). The bigger problem is that ultramafic rocks are soft. They tend to support really crumbly sea cliffs. They’re not great places for major installations.

Comment by Heteromeles

Note that those problems with wind turbines are less when put into large open areas (like large farm fields).

Comment by Barry

[…] see the end of the fossil fuel age (in the geologic near term), the end of global warming (as I posted on a while back), at least one more ice age, multiple Carrington Events, asteroid strikes, devastating earthquakes […]

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[…] release of carbon into the atmosphere over the next 200 years (this is the IPCC extreme scenario discussed here. This is the path we’re currently on. Temperatures (and extreme weather) peak between 2500 […]

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“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. ”

The time scales are key to everything here. If the effects are only noticeable on a scale of a century, it’s not as critical as if they are measurable over a decade.

Comment by Barry

It’s probably going to be a bit uglier than that. The simplest way to capture all that carbon, especially in a hot, fairly primitive world, is to plant sugar cane and use it to make ethanol. It’s a mature technology that’s actually pretty efficient. Problem is, of course, that working in the cane fields is one of the more miserable jobs in the world. One can easily predict a rather nasty Mad Max-type world set, not in a desert, but in sugar cane plantations worked by slaves, so that the overlords can drive. This would be, perhaps, in southern Canada or perhaps southern Alaska.

On the more mathematical side, it actually looks like the amount of carbon that farmers can move into or out of the air is relatively small, compared to the amount that goes in and out of the oceans. Yes, I agree that farmers and ranchers will want to capture carbon in the soil, primarily because it improves soil fertility, but our farming practices are, very unfortunately, going to play a fairly minor role in getting the carbon out of the air, especially if we really do blow all available fossil fuels and get the methane out of the permafrost to boot.

Comment by Heteromeles

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