"As even their critics admit, Levitt and Dubner have performed a useful service in drawing greater popular attention to geoengineering.  Garden hoses to the sky,however, are not the only approach.  Iron fertilization is simpler, cheaper and much more easily testable.  Most people are aware that CO2 and temperature are positively correlated in the long historical record but fewer people know that iron dust correlates negatively on the same scale - that is, temperature and CO2 levels are low when iron-dust is high.  The graph illustrates.   The basic mechanism that appears to drive the association between low temperature, low CO2 and high iron-dust levels is that iron-rich dust sometimes sweeps off the continents into the oceans where it creates a plankton bloom.  Phytoplankton take up CO2 in order to grow and as they die and produce fecal matter (I kid you not) carbon sinks to the lower depths or bottom of the ocean where it may remain for 100 to a 1000 or to even to millions of years (in the latter case eventually becoming oil). A big advantage of iron fertilization as a way of reducing CO2 is that this process occurs naturally all the time and thus may be studied.  It is also possible to run experiments.  Indeed a dozen small-scale experiments over the past decade have already been run with all showing that iron fertilization does create phytoplankton blooms and some showing carbon sequestration.  Interestingly, private firms looking for future carbon offset sources are driving much of the research into iron fertilization. Of course, all the usual caveats about uncertainty and unintended consequences apply.  Oceanus, the magazine of the Woods Hole Oceanographic Institution has an excellent issue on this topic." - Jason Wehmhoener from Bookmarklet

I met some marine microbiologists from Max Planck Institute Bremen at ISMB last summer where we talked about this specifically. They explained a couple of problems with this. Under natural conditions, only a fraction of the CO2 taken up by phytoplankton actually reaches the ocean floor, because grazers normally eat the phytoplankton and bring it back up to the surface. But under conditions of heavy fertilization resulting in a plankton bloom, the grazers die off (I believe due to hypoxia), so temporarily the CO2 does get sequestered. But without any grazers, eventually (in tens of years) the plankton die off as well, because in the absence of grazers some other nutrient is no longer cycled properly (nitrogen, phosphorus? I forget). At this point the CO2 they fixed comes bubbling up again. Another problem is the atmospheric CO2 results in acidification of the ocean, and marine organisms that have been fixing CO2 (e.g., diatoms and coralline algae) no longer do in that condition. - Ruchira S. Datta

So we're all gonna die anyways? - Jim Norris

I got all that from one lunch with people who specialize in marine microbiology and have been thinking specifically about combatting climate change. I wonder if Levitt or Tabarrok have done the equivalent, or if they automatically understand everything because they're economists and thus can do away with the need for expertise (or even data) by the sheer power of their intelligence. - Ruchira S. Datta

Jim, that doesn't follow. Actually reducing CO2 emissions is much simpler, though not easier, than these geoengineering solutions. The geoengineering solutions only *seem* simple because the complexities of ecology are swept under the rug. Economists of a certain stripe are accustomed to sweeping complexities under the rug (with regard to the economy as well), but in this case it just won't do. - Ruchira S. Datta

Do you think that's an affliction unique to economists? I see a fair amount of it in other fields too, like computers for example. - Jim Norris

It seems like we'd have much less insight into the secondary effects of any of these global warming mitigation schemes than we would if we pursued reduction in greenhouse gases in the first place. It seems like a lot of the mitigation strategies just trade off one environmental problem for another. - Jim Norris

No, it's not unique to economists--in fact I think they caught the attitude from physicists, but the attitude at least seems to work well in physics itself (as opposed to various other fields to which physicists think they can lend their powerful intelligence--see http://arxiv.org/abs...). - Ruchira S. Datta

Jim, my point exactly. - Ruchira S. Datta

Do you think they caught the "pure math" bug and lost touch with empirical reality? - Jim Norris

About computers, I think that may be at least a bit different because at least a small number of human intelligences designed the computer in the first place. - Ruchira S. Datta

Jim: totally, I wrote a blogpost about this once, way back when I used to blog: http://ruchiradatta.blogspot.com/2005... - Ruchira S. Datta

I interacted with some mathematical economists when I was doing my (pure math) thesis in game theory. One of them actually told me, "Don't use examples, they just make things more confusing." !!! - Ruchira S. Datta

I can't stand gratuitous math porn in economics (or CS or any other science). I think a lot of it just serves to make the reader feel dumb and make the author look smarter, even when it has no bearing on reality. But then again I am not a scientist. I just admire them from afar. - Jim Norris

Well, I'm trying to become a scientist, and it's a humbling experience. I do my best not to introduce gratuitous math porn. :) - Ruchira S. Datta

How close are you? How's it different than being a mere computer nerd like me? - Jim Norris

Well, I'm a research specialist, so in that sense I already am a scientist. I just feel there's an endless amount to learn, but it's also endlessly fascinating, which makes it a lot of fun. - Ruchira S. Datta

At what point do you get to be somebody and do something that anyone cares about though? Does that ever happen? Only for the lucky few? - Jim Norris

Well, I'm lucky to have already done something that some people care about (in fact we have more requests than we can keep up with), thanks to working for a great PI. I don't know when I'll get to be somebody though, that is only for the lucky few. - Ruchira S. Datta

P.I. still sounds like something out of a detective novel or TV show: Magnum, P.I. - Jim Norris

I always wanted to be a PI. :) - Ruchira S. Datta

Jim, you said "It seems like we'd have much less insight into the secondary effects of any of these global warming mitigation schemes than we would if we pursued reduction in greenhouse gases in the first place. It seems like a lot of the mitigation strategies just trade off one environmental problem for another." and I think that sounds great. The thing that stumps me is the fact that we're increasing our output of greenhouse gases, not decreasing. So, how do we pursue reduction of greenhouse gases? - Jason Wehmhoener

My cousin suggests taxing banks and using the proceeds to finance green technology transfer to developing countries: http://www.guardian.co.uk/busines... - Ruchira S. Datta

OK, interesting concept. Then how do we get the industrialized world to stop increasing emissions? Or, maybe we need a more tractable problem: Is it possible to design an experiment that demonstrates the mitigation of secondary effects given a partial or localized reduction in emissions? In other words: do we need the whole world to grow up and get along before we can prove the efficacy of any mitigation strategy? I guess I'm looking for something more of the nature of success story vs. more frightening scenarios. - Jason Wehmhoener

The article Ruchira links to mentions a "transaction tax". Can someone help me understand specifically what that means? - Jason Wehmhoener

Jason, I'll ask Arunabha what he had in mind. - Ruchira S. Datta

I'm sure I'll get in trouble for this comment, but I think stopping industrial emissions is like stopping teenage sex. You can keep telling people to abstain, or you can just give up and give everyone condoms and birth control pills. With CO2 emissions I think we're still in the abstinence camp. One day I think we will give up and decide to reduce CO2 by planting forests, increasing phytoplankton, sequestering at high density sources, etc. Also, geoengineering to reduce CO2 shouldn't be lumped into the same bucket as geoengineering that aims to cool without reducing CO2. - Amit Patel

Amit, the reason I had that conversation with those microbiologists in Bremen is because I was interested in developing geoengineering to reduce CO2 myself. I'm all for planting forests, but they take a long time to grow. In this case relying on geoengineering would be like engaging in unsafe sex in 1920, gambling that a birth control pill will be invented before an unplanned pregnancy occurs. - Ruchira S. Datta

Much simpler than planting forests and waiting for them to grow is stopping deforestation, e.g. for producing beef or biofuels, which no matter how efficient will always be net carbon positive. - Ruchira S. Datta

Ruchira, that makes complete sense. Unfortunately our agricultural lobbyists have an unhealthy amount of power and work hard to prevent any reduction in support for biofuel or beef production. How can we resist these forces? - Jason Wehmhoener

Arunabha says: "Ruchira - to clarify, my paper does not propose a Tobin tax. The Tobin tax (on international currency transactions) has been part of the debate since the early 1970s for regulating financial markets and it has been proposed at times to finance development goals. The Guardian article used a similar argument for climate change. The proposal my co-author and I have put forward for a Low Carbon Technology and Finance Facility is much more wide-ranging, covering various governance arrangements necessary to ensure the credible and timely adoption of cleaner energy technologies in developing countries. Financing (through public and private sources) is only one component. The article didn't cover all these aspects, so I thought it's best to clarify." - Ruchira S. Datta

Jason: By banding together and proposing positive alternatives. Much easier said than done... - Ruchira S. Datta

I do like the idea of pushing clean coal and nuclear (though I have misgivings about both, and feel the expense of solar and wind are justified) and it's nice to hope that if such ideas were implemented broadly enough that it would take the wind out of the biofuel sails. Still not sure what to do about the beef lobby, which is another major cause of deforestation. A large number of Americans tend to regard cheap red meat as something like a "right" (if I can safely make a rough generalization/approximation...) - Jason Wehmhoener

I do actually support research into geoengineering, biofuels, and so forth, I just think we need to combat climate change on many fronts rather than assume one of these is going to solve it. - Ruchira S. Datta

Absolutely. - Jason Wehmhoener