Category: climate change

Over at Science There’s a letter with a veritable laundry list of signers regarding the recent (and not so recent) unconscionable attack on climate science by the media, politicians, and others. It’s very much worth the time it takes to read.

We also call for an end to McCarthy-like threats of criminal prosecution against our colleagues based on innuendo and guilt by association, the harassment of scientists by politicians seeking distractions to avoid taking action, and the outright lies being spread about them. Society has two choices: We can ignore the science and hide our heads in the sand and hope we are lucky, or we can act in the public interest to reduce the threat of global climate change quickly and substantively.

Well said.

First seen over at Geotripper.

First, there was Cuccinelli and his anti-gay dickery. Then he jumped on to the healthcare reform lawsuit band wagon. Then he let us all in on his nipple phobia. Oh Ken Cuccinelli, is there no nuttery you will not force me to look at an say, “…seriously?”

And now he’s after a climate change scientist. Oh my stars and garters. Cuccinelli has come across pretty steadily as a climate change denier, so investigating Michael Mann for “defrauding taxpayers” over grants for global warming research carries a nasty whiff of intimidation. Don’t like the science? Attack the scientist’s reputation. Anyway, I think Phil lays it all out quite nicely.

I do have to say one thing I’ve found interesting on Phil’s post is the comments. Because as you would expect, the minute the Bad Astronomer tippy-tapped out:

To be clear: the climate is changing. There is zero doubt about that. None. Anyone telling you differently has an agenda to ram, and it’s one that is decidedly not realistic.

…the trolls and deniers came scooting out of their dark corners of the internet. What’s fascinating me is how disjointed some of the comments seem from the actual post.

My dramatic reenactment:

Phil: Cuccinelli is a jerk! Inhofe is a jerk! Politicians that abuse their power to try to intimidate scientists who come to conclusions they don’t like are jerks! RAR!

Commenter: But what about MY feelings????? How dare you call ME a denier!!! OMG I feel so attacked!!!

I don’t know. Maybe the people writing those comments are actually Cuccinelli and Inhofe under assumed names? Otherwise… goodness, we are getting a little defensive, aren’t we.

Conveniently enough, there’s a Scientific American article about the use of basalt as a CO₂ sink, which was posted yesterday. I suppose that using basalt for its CO₂ sponging abilities isn’t a bad second option; if nothing else, there’s a lot more basalt in the world than there is easily available ultramafic rocks. Basalt is being produced every day from volcanoes, while ultramafic melts would be very uncommon in this day and age. To get an ultramafic rock, you need a much higher degree of melting of the mantle peridotite than you’d normally get, now that the Earth has cooled off a bit.

Depending on the type of basalt, you’ll also get olivine in it, which is what I talked about yesterday as the main constituent of ultramafic rocks, the thing which weathers so nicely once you add a little carbonic acid. I doubt that you could go much less mafic¹ than basalt and still get much bang for your buck.

The reason for this comes down to Bowen’s Reaction Series, the terror of all first year students of geology. The reaction series is really just a simplified description of how magmas crystallize, because different minerals are stable at different temperatures and pressures. We’re most concerned with the left side of the series, in this case.

So let’s pretend we’ve got some mafic (but not ultramafic) magma, which spews to the surface and becomes lava. The first thing that will crystallize in it as it starts to cool is olivine. As the lava continues to cool, some of the olivine (not very stable at these low pressures) will react with the remaining melt and begin forming pyroxene. More cooling, and the pyroxene starts converting over to amphibole. Melt composition also plays a big role, but that’s getting a little too complicated for a Tuesday before I’ve had lunch, I think. By the time all your lava has cooled down, you’re going to end up with a mixture of what’s more stable at the surface, such as pyroxene and amphibole.

That’s generally how the reaction series works. The important thing to keep in mind is that the higher you are in that reaction series, the less stable the mineral is at the surface. And the less stable it is, the easier it is for carbonic acid to come along and work its magic. Ultramafic rocks are ideal for this because they’re mostly olivine. Depending on the type of basalt, there are still a lot of minerals that break down very easily, such as pyroxene – and some basalts do have significant amounts of olivine in them still.

This still has the same pitfalls and questions as using the ultramafic rocks, I think. The biggest being, of course, that if you think it takes a long time for an ultramafic rock to weather, it’s going to take even longer for basalt.

I’m also really wondering about the one sort of throw-away statement at the end of the article:

Already, a proposed coal-fired power plant proposed in Linden, N.J. includes plans to pump captured CO₂ emissions into an offshore sediment, albeit not a basalt one.

Putting aside the the cringe-inducing phrase “an offshore sediment,” I’m wondering what exactly the goal is, there. Are the sediments in question ones that they expect the CO₂ to react with? Are they just hoping the sediments are going to hold on to the CO₂ long enough that it’ll be someone else’s problem, which is often the goal when we’re talking about injecting carbon down somewhere deep in the ocean? That’s a little worrying.

1 – Just in case you didn’t know, all this “mafic” business is just a reference to the major non-silica components of the rock. Mafic is shorthand for magnesium/ferric (ferric meaning iron) since there’s a lot of those elements in this sort of rock. You’ll also hear “felsic” which is shorthand for feldspar/silicate, which you find in abundance in rocks like granite.

Io9 did a post yesterday about peridotite and its ability to soak up carbon dioxide, and mentioned in the first paragraph that no one’s talking about it. And another article that says we’re not excited about it.

I imagine a lot of people haven’t even heard of peridotite, or don’t know what ultramafic rocks are, which is fair enough. Most people aren’t geologists, and have a hard time getting excited about rocks. I actually hadn’t heard of looking at ultramafic rocks for carbon sequestration until I took introduction to Geochemistry last year. After that, yes, I thought it was a pretty exciting concept.

Now, the reason we were talking about this in geochemistry is that the carbon sequestration comes down to a very basic chemical reaction that occurs every day – the chemical weathering of rocks. Most rocks in our lives are some form of silicate; their chemical formula is SiO₂ plus some other junk, and the crystalline structure is usually the silica tetrahedra arranged in different ways around the other junk. Most chemical weathering of these silicates comes from CO₂ dissolving in rain water to make carbonic acid, H₂CO₃. Rain is actually naturally a little acidic, since it’s made up of water plus a little carbonic acid. It falls, runs over rocks, and then you end up with something like this:

Mg₂SiO₄ + 4CO₂ + 4H₂O ⇌ 2Mg²⁺ + 4HCO₃^– + H₄SiO₄

Where the water and carbon dioxide are what make up the carbonic acid. In this particular equation, the rock in question is olivine, the main constituent of peridotite. So basically, it’s:

Olivine + water + carbon dioxide ⇌ magnesium ions + bicarbonate + silicic acid

So chemically, you can use this kind of reaction to get CO₂ out of the air. And peridotite is certainly a good candidate for this kind of reaction. Olivine has a mineral structure that’s basically individual silica tetrahedra jumbled together; it’s not really stable at surface conditions, and it’s easy for the tetrahedra to get picked off by whatever happens to come by. That’s why olivine weathers away much faster than something like quartz, which has a very organized framework and doesn’t allow a lot of room for party crashers. Once you’ve got the olivine broken down via this process, then you can separate out the ions and acid. The magnesium, you could make in to salts, or perhaps there’s a good industrial use for it. The bicarbonate just needs some calcium, and then you end up with limestone, which is the end result we want for getting the carbon chemically locked away. The silicic acid could be precipitated in to amorphous silicate if nothing else.

Honestly, I can’t say why people aren’t excited about this possible solution to getting carbon out of the air. It’s got its problems that need to be figured out for sure, though not necessarily more than any other proposed sequestration method. Off the top of my head:

The reaction is normally extremely slow, as noted in the articles, so you do have to find a way to speed it up. And in so doing, a way to speed it up that doesn’t involve producing more carbon via energy usage than what you’re taking out of the atmosphere.

Once you’ve got your schmutzed-up former olivine, you still have to put it somewhere. One suggestion my geochemistry teacher had was to just toss it in to old mines, which isn’t really that bad of an idea. But there’s still a question about hauling tons and tons of rock anywhere, to be honest.

You’d need to have a good, energy efficient way to get carbon out of the atmosphere and then dissolved in to your water.

And I’m sure there are more questions than that. But I also don’t think these are more difficult questions than the ones that come with any proposed carbon sequestration scheme. It even has its advantages; once your carbon is chemically locked in to limestone and you toss that limestone down an old mine, you don’t really have to worry about it again. The dissolution of limestone does release the carbon, but you’re not going to have to worry about that until millions of years in the future, when there’s been some uplift and the contents of the old mine are exposed to weathering. I’d say that’s easier to deal with than figure out how to keep CO₂ in gas form from escaping a reservoir you’ve injected it in to.

Most people I’ve explained this to have thought it was actually a very exciting idea, if one that’s so far just on paper. The big thing is that very few people have even heard about it, as is pointed out in the articles I’ve linked to. Maybe it’s because it’s difficult to get most media excited about talking rocks, unless we’re talking molten rocks that are poised to destroy a town, and then they’re all over it. Of course, one might argue that it’s more important to pump money in to research on finding energy sources that aren’t going to produce so much carbon dioxide. Fair enough, but until we get there it really wouldn’t hurt to figure out how to stuff at least some of that excess CO₂ back under the global couch cushions, so to speak. Or I suppose there are some that might say that none of this is a matter of concern, but I think I’ve already established that I wouldn’t want to sit next to them on the bus anyway.