I had a short story idea about a fusion-powered machine that made carbon nanotubes for a space elevator out of atmospheric CO[sub]2[/sub]. I think my idea might become reality around the same time as Dyson’s trees.
All because you can find a difference between an analogy and the actual thing does not make the analogy meaningless. That is why it is an analogy. The question is whether it is materially-different and I don’t see how it is because the point is that we don’t want more and more CO2 in the air, which is what we are getting by liberating CO2 long locked away at a rate much faster than the biosphere and hydrosphere can take up this excess.
So, the point still stands that there are negative consequences to emitting this CO2 into the atmosphere and unfortunately these consequences are externalized. As long as we don’t put a cost on CO2 emissions in the marketplace, the necessary technologies to reduce or sequester these emissions are unlikely to be developed and brought to the market. This is all Econ 101 stuff.
Thanks, jshore. All of that would make perfect sense if we had any evidence that there was a negative consequence to changing the atmospheric CO2 level from 0.03% to 0.04% … I keep asking for evidence, and people keep giving me the results of unverified, untested climate models. If someone can’t tell the difference between evidence and climate models, I guess your claim would be perfectly logical to them.
I, however, have written too many computer models of various systems to have any faith in them whatsoever. This is particularly true when we are trying to model the climate, arguably the most complex system to ever be attempted. Climate contains significant processes at spatial scales from the atomic to the planetary, and at temporal scales from microseconds to hundreds of millennia … good luck.
But even ignoring the complexity, the climate models have not been tested, verified, or quality assured as much as the software that runs a high-rise elevator … and people want me to treat their results as evidence?
Not.
The real fun part starts when the tinkertoy models disagree with the evidence … and the modelers say that the evidence must be wrong. There’s a good discussion here (pdf), and a scorecard here.
Best regards,
w.
Not necessarily. Where do you think the oil we’re using now came from? A certain percentage of biomass gets buried, or sinks to the bottom of the ocean and stays there.
But it is a fairly small percentage of biomass that is permanently sequestered. Young forests absorb CO2 and grow, then when they mature they stop absorbing much CO2 relative to their mass. Eventually the dead and rotting material on the floor of the forest releases back the CO2, or the periodic forest fires sweep through and convert it back into CO2 rapidly.
It turns out that tree farms and new growth forests are actually much better from a CO2 absorption standpoint. we grow trees, which absorb CO2. Then we cut them down and turn them into lumber, paper, and pulp. Much of this stays out of the atmosphere for a long, long time. There are still wood products around that was cut down a thousand years ago. A lot of plant material winds up in landfills, and modern landfills are often sealed and buried when they are full and the CO2 remains sequestered.
I don’t think Dyson was saying that you’re storing it in living things. The living things are just an intermediate. It’s not hard to sequester carbon from a forest. Hell, you could set up huge coastal tree farms, cut the trees down when they pass peak CO2 absorption, throw them on logging barges, sail them out into the deep ocean or into the great lakes, and dump them. There’s a company right now making good money harvesting lumber that sank in the great lakes when logging ships went down 100 years ago. The stuff is preserved perfectly.
The big question is how much carbon you could sequester with reasonable effort, and to me, that number looks way too small. The amount of carbon we’re talking about is immense - gigatonnes per year.
I think you’d have much better success finding a way to seed a natural process to d it all by itself. For example, if you could bioengineer a type of plankton that absorbed as much CO2 as current varieties but required fewer nutrients from the water, the ocean might support a biomass of plankton much greater than it can now. Or, you could engineer a type of plankton that works the same way it does today, but when it dies it sequesters all its CO2 instead of just a tiny fraction - say, by having it form a dense shell around itself in the final stages of life so it sinks to the bottom of the ocean.
Or, if we could figure out how to make ocean power systems which utilize the thermal gradient of ocean water to make power, we might find they are actually carbon negative - the upwelling of cold, nutrient rich water they produce would stimulate blooms and sequester more CO2. They would also stimulate the creation of large fish populations, which we could harvest for food and cut back on red meat, which would reduce the amount of methane we produce.
I tend to agree with this. At least, so long as we’re still emitting massive quantities of CO2. Such techniques might be useful if we get off of fossil fuels, and find the earth too hot at that point. Now much more modest sequestering programs might help restore a balance sooner than doing nothing at all.
While I don’t see the theoretical problems that Archer sees with the Dyson proposal, I would agree that the proposal is impractical. And in fact, we don’t even understand the trees we have:
Billions of trees around the planet, billions of tonnes of biomass, all carefully maintaining a ~ 21°C temperature … anyone want to guess the effect of that on the global temperature?
And for bonus points … how many climate models include this effect?
w.
intention: If we had to include every conceivable effect when we model a physical system in order to get reasonable results, then modeling would simply cease to be a useful enterprise ever because there is simply no system in which we can do that!
jshore, this is quite true … but the trick is, as always, to figure out which effects are significant and which are not. It is not enough to just say, as you have done, that there are significant and insignificant effects. Before we can believe the models, it is necessary (but not sufficient) to show that recently discovered or ignored effects such as these are not significant.
All the best,
w.
Dyson’s proposal is essentially a rather complicated form of solar power. We burn fossil carbon for energy, to make CO2, and use solar power via plants to convert the CO2 back to high-carbon solids. Which plants do anyway, sequestering the CO2 in a variety of cellulosic composite materials with many useful properties, known collectively as “wood.” Genetically modifying plants to sequester CO2 in higher density forms, and/or even more useful forms (e.g. a “superwood” with superior mechanical properties, that we can use instead of carbon fibre composite) is still limited by the fact that you need sun shining on leaf area to run the whole thing.
Additionally we’d need to harvest the high carbon solid, be it wood or some GM product, and stick it somewhere. Sinking logs into the sea is just insane - better to burn them for energy and leave the coal they replace in the ground. But we’d do even better devoting a similar amount of land area to solar generation that we do to agriculture, and simply burning less fossil fuel.
If our high-carbon solid is a useful material in itself, the picture improves. It could be argued that we should use wood more in construction, sequestering the carbon for hundreds if not thousands of years. (It’s rather interesting to note that Venice is sitting on an underwater “forest” of wooden piles around 1000 years old. Wooden constructions can last a while!) While no solution, it certainly wouldn’t hurt. Sustainable logging allows the growth of new forest, which turns CO2 into more wood.
A biological high-carbon solid that may well be useful enough in itself to sequester in large amounts is charcoal, powdered and mixed into topsoil. The agricultural benefits of this are apparently impressive and the material is stable for thousands of years. If the process was industrialised - e.g. sustainable logging, the harvested logs turned to charcoal on a large scale and powered by the wood gas generated by the process itself, then we could in theory sequester a fair quantity of CO2 in a short space of time. The carbon would be stored in a few extra inches of highly fertile topsoil in the world’s agricultural land, and the new forest growth from the sustainable logging would pull CO2 out of the air.
I think what you guys are saying, in more general language, is that if we figure out how to produce biofuel on a world scale (basically, if we can do exactly what we hope), we can just keep making it and burry it where all the oil used to be. I think if it was said like that, the point would be a lot more intuitive to people. Of course, that would just be a reason for more uninformed criticism.
(P.S. i guess maybe you like the whole ‘future biotechnology’ ‘plastics’ etc facet of the argument… but really that makes it a lot more idealistic and unrealistic. What are we going to do with 300 gigatons of plastic? Ditch concrete and make all our buildings out of PVC? Well… i guess… maybe. But for now, talking about making and sequestering biofuel is a more down-to-earth angle.)
Oh, man, let me tell you about the elevators in the last high-rise I worked in. We were on the top floor, and during lunch the damn things would never come to us. They got filled up or something, I don’t know. It’d be 20 minutes past noon until the lunch rush abated and we could descend. That elevator software was CRAP.
Anyway, I have a question that doesn’t get addressed often. It’s probably not addressed because it’s not politically correct, but here goes anyway:
Plants love CO2. They need less water, they have more food. In fact this whole discussion about plants’ role in global warming’s future is about how much more of then there’ll be. So, to sum up, what’s the prospect for global warming making the world a greener, lusher place?
Alex, well the fact that the biosphere has been absorbing some of the CO2 we have been emitting is indeed evidence that elevated CO2 levels have increased the biomass somewhat. However, there is a limit to how much plant growth can increase under higher CO2…Basically, they can do so fairly significantly in cases where that is the limiting factor, but not in cases where something else (like water) is the limiting factor…or until this something else becomes the limiting factor. I believe that there are also concerns that some of the plants most benefitted by increasing CO2 may be the ones that seem to adapt well in lots of environments and we tend to call “weeds”.
Well I’m not one to get snobbish about such things. If the stuff is green and doesn’t give me a rash, I enjoy it.
Alex Dubinsky, in addition to jshore’s excellent summary of plants and increased CO2 levels above, there is more information here.
My best to all,
w.