Filed under: Geoengineering, Interventions in the carbon/climate crisis, Published stuff
It is time again for the annual feast of fun that is Time’s Heroes of the Environment list. As always it is a thought provoking reminder of how narrow my environmental issues are. Climate and energy issues dominate what I think of under that rubric but here there is lots of room for good old fashioned pollution: mines, dirty rivers, rubbish and the like. Not to mention bloody organic farmers, and various people who would not really make my list (Pen Hadow? Really?)
But climate and energy do top the bill: Mohamed Nasheed of the Maldives leads off the whole package, and there’s a nice spread about Joe Romm, who gives his take on the honour here. (Nice note of irony: the piece on Joe Romm is written by Bryan Walsh, eviscerated by Joe earlier this year for a piece that took the Breakthrough Institute’s line on energy R&D; in last year’s Heroes Bryan profiled the Breakthrough Institute’s founders Ted Nordhaus and Michael Shellenberger.)
My contribution this year (following Jim Lovelock in 2007 and Kim Stanley Robinson in 2008) is on David Keith, who I imagine is probably suitably embarrassed by the whole thing; but to my mind deserves the recognition. His heroism consists of thinking hard and clearly about things other people are hardly thinking about at all. That has let him do a great deal to help frame and further the debate on geoengineering, which needed to be done, and now he’s pursuing ideas about direct air carbon captur, which again can but benefit from the serious attention. It also makes him one of the best people to talk to about climate and energy issues, bar none. Excerpt:
Early success in pure physics (his graduate project, supervised by a professor noted for his mentoring of future Nobelists, was a long-awaited experimental breakthrough in atomic optics) did not satisfy him. Climate work promised a greater opportunity to do good while at the same time throwing up what ambitious physicists always want most: questions no one yet knows the answers to.
Soon he was working on nitty-gritty climate-modeling problems while learning economic and policy analysis. That breadth has helped him communicate climate concerns to the often skeptical energy industry; it’s also part of why he is listened to by people like Bill Gates, who relies on meetings organized by Keith to stay up-to-date on climate science. “While he’s got informed and strong opinions,” Gates says, “he’s also incredibly open-minded, pointing out the unknowns in his opinions and just as readily pointing out the merits of others’ opinions.”
Image of David Keith by Ewan Nicholson, used with permission, all rights reserved
Filed under: Geoengineering, Global change, Interventions in the carbon/climate crisis, Trees
An interesting paper in Climatic Change: Irrigated afforestation of the Sahara and Australian Outback to end global warming by Leonard Ornstein, Igor Aleinov and David Rind Doi: 10.1007/s10584-009-9626-y. (Mason Inman has a nice write up with some background and comment over at ScienceNow; [update] and corresponding author Len Ornstetin chronicles the idea’s rocky research road on his own site). The central idea is that with enough irrigation you can turn big deserts into big forests: forests big enough to suck up a large part of total carbon dioxide emissions for decades or even centuries. I think that you can take this notion as a serious plan, a thought experiment, a jeu d’esprit, a warning or a jumping off point, depending on predisposition. Aspects of all that in what follows.
Here are the basic numbers: The Sahara is about a billion hectares in area, on which you could fit a trillion eucalyptus trees. Those trees, if working flat out, could each put on twenty kilos of biomass a year. If roughly half that biomass is carbon, that would mean a net annual sink on the order of ten billion tonnes of carbon. That’s about the amount that humans currently emit.
To create such a forest in a century, you would have to plant as many hectares of trees every year as are currently lost to deforestation worldwide. And, even harder, you’d have to provide them with what they need to order to grow. You need a great many things to turn a desert into a forest — soil nutrients, microbiota, possibly pioneer plants, a compelling reason for doing the work, and so on — but the biggest hurdle, pretty obviously, is water. Eucalyptus, the authors say, needs about a metre of rainfall a year. For a billion hectares, that’s 10 trillion tonnes of water. The authors assume, reasonably for all that I know, that if you have smart irrigation getting the water to just where it is needed you can get away with half that amount. Even so, even the vast aquifers beneath the Sahara don’t contain the amount of water required, so it will have to come from desalination plants on the and be pumped it up to where it is needed (the average elevation of the Sahara is about 450m). The size of this undertaking — more than 50 new Niles, flowing in reverse — may explain why the authors feel they need to use that fine old-school term “terraforming” for their undertaking. The power requirement, if I’m reading their figures right (4.04kWh/m^3 fresh water delivered), is a bit to the north of 2.2 terawatts, about 40% of it for desalination by reverse osmosis and about 60% for pumping.
The world’s electricity generators currently provide about 18,000 TWh of energy, which averages out at 2TW of constant supply. So in energy terms the desalination and pumping needed for the Sahara forest would use a bit more electricity than the world currently generates for every other purpose. This unavoidably sounds nutty. But that is at least in part because of the nuttiness of the situation, rather than its proposed solution — the nutty situation in which we burn fossil carbon at tens or hundreds of thousands of times the rate at which it is sequestered over geological time. If humanity insists on putting so much carbon dioxide into the air every year that it would take a brand new forest the size of the Sahara to suck it all up, then that’s where the madness starts. That creating such a forest would have to be a large undertaking — large in terms of the whole world economy — is just a consequence of the initial folly.
And in practice the investment would be smaller. A nice thing about forests is that they can go some way to creating their own weather, and the authors have looked at this effect with some climate modelling work. If a forest with irrigation dampened soil is imposed on the Sahara, rain begins to fall, in some places as much as a metre of it every year. This rainfall doesn’t obviate the need for irrigation, because it is strongly seasonal — basically an extension of the West African monsoon of April to November. But it might significantly reduce the irrigation requirements. Maybe you could get away with just a terawatt…
The Sahel, to the south of the Sahara, also gets damper in those enhanced and extended monsoon rains, which is definitely a plus, I’d guess, and the African Easterly Jet, a feature which is driven in large part by the temperature contrast between the desert and surrounding land, seems to more or less vanish. Since a large number of Atlantic hurricanes get their starts as kinks in the AEJ, that might be a pretty significant change, too. Beyond that, the rest of the world seems pretty much unaffected. In particular, the authors say that their models show no additional warming that might be laid at the door of the change of albedo which comes with replacing light desert with darker trees. (I think this fits with the 2007 Bala et al paper in PNAS, which suggested that warming associated with afforestation would be due to changes in boreal, rather than tropical, forest cover).
There is, however, a fly in the ointment. The Bodélé depression in Northern Chad is only a small part of the Sahara, but it is the world’s greatest source of mineral dust, with the winds drawing some 700,000 tonnes a day off the surface. According to Koren et al in ERL, 2007 40 million tonnes of dust a year travels from the Bodélé to the Amazon rain forest, half the total annual mineral inputs into the forest basin (the dust fertilises the mid Atlantic, too, and it may play a role in abating hurricanes too — Jim Giles wrote a lovely piece on this for Nature some time back). There’s a real chance that this dust is crucial to maintaining the soil fertility of the forest, and even if the Bodélé itself were left unirrigated and unforested, the increase in precipitation all round it, and the wetter atmosphere downwind of it, would probably shut it down as a dust producer. If growing a forest in the Sahara hurts the one we already have in the Amazon it obviously becomes a less attractive proposition (though if we are going to lose the Amazon forest anyway, things might look different…). That said, if you are pumping trillions of tonnes of water across continental scales, thenpaying to air dump a few tens of millions of tonnes of fine-particle mineral fertiliser upwind of where you want it is hardly going to break the bank.
Something the authors don’t look into is that the higher the CO2 level in the atmosphere gets, the easier this all becomes. Higher carbon dioxide levels make plants more water efficient, all other things being equal. All other things are not, necessarily, equal — higher CO2 also makes things hotter, which plants don’t much care for. In a world with some solar radiation management, though (such as aerosols in the stratosphere) all things might indeed be kept equal, or at least temperature might be. Martin Claussen has been working for some time on the idea that the Sahara is a “tipping element” in the climate regime, one that can be pushed from a dry state to a wetter one relatively easily. In a more carbon rich but not-too-hot world the circumstances might be right for it to tip the other way, and it might take rather less than a 50-Nile terraforming project to nudge it over.
In the final analysis, I don’t think I take this paper very seriously as a practical proposition. Doubling global electricity generation for a single project seems far fetched. For such a thing to be put anywhere near the top of one’s list of African infrastructure investments would require that a great many other large and important development initiatives (provision of power, water, roads, cold chains, vastly improved agronomical advice, etc to the vast majority of the population, for starters) would already have had to have been put in place. But it’s kind of nice to imagine a world in which we were wealthy and together enough to have actually taken the pressing need for those changes to heart, and were thus in a position to consider greening a great desert too.
And regardless of practicalities I think there’s real value in taking the analysis further. A big idea like this throws off many fascinating questions that force you to look at the earth, and what we know about it, in new ways (or old ways but with a new twist):
What polycultures would you build the new forest with? (all-eucalyptus-all-the-time is fine for first calculations, but doesn’t sound like anyone’s idea of a proper landscape. Baobabs? Laurels? And what fauna might be good, or bad?)
What genetic engineering — reduced flammability, higher albedo leaves, more refractory soil carbon, who knows what else — might help?
How much bioenergy with carbon capture could be built into the scheme, perhaps initially to power some of the inland the pumping stations?
Can biochar help? (and a million other soil-creation questions)
What are the best silvicultural ways to make the new woodlands pay, as that is something people by and large like their environments to do, and can there be room for some agriculture too?
How could local people best be convinced this was a good idea? And what are the property title reforms that would be prerequisite?
If the AEJ stops, do hurricanes stop too? Or does some other mechanism initiate them, maybe somewhere else? And does the dust really have an effect?
When the Sahara was wetter and less dusty in the past, did the Amazon actually suffer from lack of nutrients? (I think there is actually some research already out there on that — but can’t offhand think where)
How can the transformation be made stunningly beautiful?
What regions and landforms do you want to keep as monuments/heritage sites/national or world parks? There would undoubtedly be a real aesthetic/biodiversity loss in the removal of the desert, not to mention risks to some utterly wonderful buildings.
How to stop the Fremen becoming soft and decadent now that Arrakis has become a land of milk and honey?
and so on.
In particular, it would be nice to see some analysis of halfway houses; where in the Sahel and points north might merely huge, as opposed to planet-sized, afforestation be attempted, and what would be the costs and benefits? It is possible to transform land on very large scales, if not quite this large: 40m hectares of the Brazilian cerrado have been brought into agricultural production over the past fifty years. Can afforestation/silvicultural interventions on such scales ever make sense? And where else might be suitable for such things?
And on the topic of where else: My apologies to any Australian readers for not going into the paper’s analysis of foresting the Outback in addition, or as an alternative, to the Sahara. Basically the arguments are largely the same but the costs and effects are a bit smaller. There’s also a risk of interfering with El Nino that would definitely merit further attention. If anyone wants to blog more on that aspect of the subject send me a link and I’ll post it up here.
Image credits: Eucalyptus trees at the top from Big Lands Brazil, who would like to sell you some…; Bodele from Charlie Bristow, reused with permission; Tree of life from Flickr user Solvo under Creative Commons license
So yesterday the Royal Society’s report on geoengineering came out, with a launch event and a press conference. It (82pp PDF, press release) is undoubtedly the best overall briefing on geoengineering technologies and their policy/governance implications that you can find right now; John Shepherd and his team did a comprehensive and thoughtful job.
I’m sure that when I get into it in depth I’ll find lots of interesting gems, but here are some highlights
- The overall frame is that none of these options in any way takes the place of emissions control.
- The report makes a clear distinction between carbon dioxide reduction (CDR) techniques — afforestation, burning biomass with carbon capture, biochar, “artificial trees” (possibly the most misleading label any technology is currently labouring under) and so on — and “solar radiation management” (SRM) techniques — sulphate aerosols, cloud-whitening, mirrors in space, etc. CDR interventions will always be very slow to have their effects, while some SRM techniques could be very quick.
- Some of the CDR techniques — those that involve no major interventions in ecosystems — are seen as pretty much unproblematic, if not currently affordable; transnational issues only arise if they start to reduce the carbon dioxide level too far (whatever that might be). CDR that gets into major ecosystem issues — eg ocean fertilization techniques — give greater cause for concern.
- Pretty much all of the SRM techniques are seen as having significant risks, except for painting roofs white, which simply doesn’t do much good.
- In CDR, two technologies stand out: direct-air carbon capture and BECS, biomass energy with carbon sequestration. Both cost a fair bit, but a decent carbon price would help sort that out. BECS has the advantage of producing energy rather than using it; but though direct captureuses quite a lot of energy has the advantage of a footprint that is hundred or thousands of times smaller per tonne of carbon sucked up. Both assume that there are places to put the carbon once it has been purified.
- There’s also more discussion than I’ve seen elsewhere of “enhanced weathering” — reacting carbon dioxide with rocks ground into the soil and things like that. Low on affordability and readiness, and requires a massive new global mining industry, but since it can scale up in a big way worth keeping an eye on…
- In SRM, stratospheric aerosols are the most impressive option, ranking as high as or higher than anything else with comparable potential. The impacts on other things, though, most notably the hydrological cycle, are a worry. In the 1990s the sulphates from Mt Pintaubo not only dimmed the sun — the also dried the world’s rains and reduce the flow of its rivers. Working out how much this effect matters is probably the most important open scientific question in geoengineering (that’s my opinion, not something the report says).
- Cloud-whitening proponents will be disappointed, possibly a little aggrieved, at being seen as consierably less effective than aerosols; proponents argue that they can offset a doubling of CO2. On the other hand the report is kinder than one might expect to space-based systems. “Kinder” here means saying someone should go and think about everything so far proposed in that arena a bit more seriously for a few years and then come back and make a case, rather than simply laughing.
- There needs to be a thorough audit of the many international agreements currently in place for other reasons — the UN framework convention on climate change, the London convention, the Montreal protocol, the law of the sea, the convention to combat desertification, the outer space treaty, the convention on biological diversity, and various others — to see which currently have bearing on any of these techniques, and how they could be used to exert control or to provide incentives.
- The UK should commit to £10m a year for ten years in research; worldwide a suitable figure might be ten times that. As John Shepherd put it, this would be ten times current spending on such things, a tenth of total climate research spending and a hundredth of spending on energy technologies.
All reasonable stuff, it seems to me, and well referenced if not well illustrated. The launch event and press conference, though, did feel a little stifled by worries about being seen as championing the technologies under discussion. The press release was actually headed “Stop emitting CO2 or geoengineering could be our only hope”, framing geoengineering principally as a threat. A little more of a sense that some or more of these technologies might be useful adjuncts to emissions reduction rather than a dread alternative could have been helpful — a little less of a sense that they all must be bad. Interestingly, one of the people discussing the issues at the launch event did go further than others in this, pointing out that if you want to get carbon dioxide levels low enough to do something about ocean acidification you are undoubtedly talking about CDR, not as a “plan B”, but as part of the basic strategy. That was John Beddington, the UK government’s chief science adviser.
Yesterday Dan Lack of NOAA gave a talk to the NCAR media fellows about his work on pollution from shipping, and told us something I found pretty flabbergasting. Last year the International Maritime Organisation, as part of a number of measures aimed at air pollution, decided to do something about the sulphur emissions from shipping by reducing the amount of sulphur dioxide permissible from 4.5% today to 0.5% in 2020. This would have great benefits; sulphate pollution, and associated particulate matter, cause significant health problems. According to a new paper in Environmental Science and Technology by Winebrake et al, if in 2012 the world’s shipping complied with this requirement, the associated sulphate pollution would cause 46,000 premature deaths; if that shipping used today’s higher sulphur fuels the death toll would be 87,000.
However, sulphur emissions from shipping have another effect: the sulphate aerosols that form from the gas make the oceans cooler by increasing the cloud cover above them, as the image at the top of this post shows. The effect is large enough that shipping cools the planet through sulphate aerosols much more than it warms the planet through greenhouse gas emissions. In a companion paper in Environmental Science and Technology, this time with modeller Axel Lauer as first author, the same team looks at this effect. Using the same 2012 scenarios they used for the health figures the researchers find that the cooling effect using fuel like today’s, expressed in terms of radiative forcing, is about 0.57 watts per square metre. The cooling effect if everyone uses the new low sulphur fuels is 0.27 W/m². That means a difference of 0.3 W/m² — which is to say that that’s the amount of warming that switching to low-sulphur fuels would produce.
What does a radiative forcing of 0.3 W/m² mean? Here’s a chart from the IPCC showing the radiative forcings associated with all human climate-changing activities as of today. The total (with biggish error bars) is 1.6 W/m², which shows straight off that 0.3 is quite a lot. It is, for example, twice the amount of forcing as is due to N2O, 60% of the forcing due to methane, and the same as the amount due to halocarbons (HFCs). A huge amount of money is currently being spent on the HFC problem.
Put another way (and I calculated these numbers myself, so please check and correct if you have the necessary skills) 0.3 W/m² is the radiative forcing you would expect if you dumped 47.5 billion tonnes of carbon (in the form of carbon dioxide) into the atmosphere, raising the concentration of CO2 from today’s 387 parts per million to 409 parts per million. That’s well over a decade’s worth of carbon emissions and an enormous amount of warming for the IMO to have committed the world to with no-one, as far as I can see, paying very much attention. (The most obvious environmental response to the IMO changes, from the Clean Air Task Force, was to applaud the health effects of the cuts in sulphur while deploring the lack of action on greenhouse gases and not mentioning the cooling issues at all. If you accept Dan Lack’s figure of just 0.06 W/m² for the total warming from shipping, that seems an odd omission.)
Now there are obviously complexities and caveats. This is just one modelling study — but its figures for the amount of cooling due to sulphur fit with those quoted by of others, such as Dan Lack. Taken at face value it would imply both that the total cooling effect of sulphur on clouds was probably greater than the IPCC best guess, and that sulphate from shipping was responsible for a disproportionate amount of it. But the IPCC’s guess has big error bars, and you would indeed expect sulphate from ships to be peculiarly effective — it gets sprayed into places where the clouds are very susceptible to such things. (This is the effect that John Latham’s geoengineering scheme based on cloud brightening seeks to emulate). The papers compare effects for 2012 not 2020, which is when the regulations will call for al fuel to be low sulphur, but does anyone expect less shipping in 2020 than 2012?
So is this a matter of balancing 40,000 lives a year against a decade of global warming? Not necessarily. There is another sulphate reduction option: burn low-sulphur fuels when close to land, and ordinary fuels when far off. There are already some areas where ships have to use low sulphur fuels, and they could be extended to all the places where the sulphate is likely to do its greatest harm. In further scenarios the authors of the two papers looked at a world of 2012 in which ships’ sulphur was reduced to 0.5% or even 0.1% when within 200 nautical miles of land, but left unchanged in mid voyage. In terms of fatalities the 0.1% in coastal waters is slightly better than 0.5% all over the place (44,000 deaths), 0.5% in coastal waters is slightly worse. In terms of cooling these two options are lower than business as usual but higher than a global reduction to 0.5% — their forcing is 0.45-0.48 W/m².
Low-sulphur fuels in coastal areas could lessen the warming associated with a global sulphur reduction and still save as many lives — or more. They would impose other costs, though. Getting sulphur out of fuel costs money, and this might make getting down from 0.5% to 0.1% an issue. Ships would have to carry two different types of fuel, which is also problematic, though not impossible. And going low-sulphur still deprives the world of a lot of cooling, even if the regulations only apply in coastal waters. That’s largely because most shipping is coastal. (This suggests that forcing ships to take longer, less coastal routes — to put out straight to sea where possible, and spend more time further from land — might be an option. Again it has costs.)
Beyond preferring coastal controls to global controls I have no real policy case to make here. I’m aware that there is in general a trade off between air quality reasons for reducing sulphates and the possibility that their cooling effects can be climatically helpful. But the fact that this measure involves reducing sulphur emissions in places where they do no harm (the mid oceans) and where their cooling effects are greatly enhanced (by the presence of low clouds they can brighten) makes the question particularly pointed. I have no way to balance the advantages of reduced global warming against the advantages of decreased mortality. I don’t know who has. But I do think that it’s kind of extraordinary a regulatory change with this much effect on global warming could be made with so little apparent fuss.
And I also think this all makes the case for experiments with Latham-type techniques that brighten clouds to cool the seas even stronger than it already is. If, for good reason, we are actively reducing the amount of cooling provided by shipping, surely we should at least look at possible ways of putting it back?
“Mitigating the Health Impacts of Pollution from Oceangoing Shipping: An Assessment of Low-Sulfur Fuel Mandates”, Winebrake, J. J. et al, Environ. Sci. Technol., 2009, 43 (13), pp 4776–4782
“Assessment of Near-Future Policy Instruments for Oceangoing Shipping: Impact on Atmospheric Aerosol Burdens and the Earth’s Radiation Budget” Lauer, Axel et al, Environ. Sci. Technol., 2009, 43 (13), pp 5592–5598
Filed under: Interventions in the carbon/climate crisis
My friend Gideon Rachman was so kind as to quote me in his column in Tuesday’s FT, “Climate activists in denial“, to the effect that
Building two terawatts of nuclear capacity by 2050 – enough to supply 10 per cent of the total carbon-free energy that’s needed – means building a large nuclear power station every week; the current worldwide rate is about five a year. A single terawatt of wind – 5 per cent of the overall requirement – requires about 4m large turbines.
Some people have since been in touch to get a source on those claims (a book proposal, as it happens: Gideon and I have the same agent) and I thought I might as well post the answer I emailed them here, as well.
They’re rule of thumb figures — by which I mean certainly good to an order of magnitude and ideally to a factor of two or so — derived not from research per se but from simple arithmetic.
Current world energy use is about 13TW. With realistic/optimistic growth figures for industrialising and less developed economies, 20TW in 2050 seems a fair ballpark. It also seems fair to think that electricity (and thus nuclear reactors and windmills) will become a larger part of the mix.
As a rule of thumb, a nuclear station will be rated at about a gigawatt of electric power (IAEA figures that my former colleagues and I quoted here http://www.nature.com/news/2008/080813/full/454816a.html have 439 power plants producing with a combined capacity of 370 GW, for an average of 840 megawatts each, but newer stations are on the larger side, with the new Westinghous design at a little over a gigawatt and the new French design at a gigawatt and a half or so) and it will actually supply almost that much (nuclear power plants in mature systems typically run at almost 95% of the stated capacity, with a month of downtime every year and a half). So to build 2 terawatts of capacity (10% of 20TW) you have to build roughly 2,000 stations. 2,000 stations in 40 years works out at 50 stations a year.
By a large turbine I meant a 1MW installation. You need a million of those for a terawatt of capacity. But unlike nuclear stations, wind turbines do not produce at their rated capacity very much of the time. On the basis of a system generating 25% of its stated capacity, which is pretty common, you would need 4TW of capacity for a terawatt of generation — hence four million turbines.
Those wind figures are, with hindsight, a little pessimistic. Though anyone who has seen one will agree that a 1MW turbine is large, big wind installations these days, especially those offshore, tend to work on the basis of 1.5MW – 3MW turbines, sometimes even more. And a good farm well placed might generate as much as 33% of its stated capacity. With 3MW turbines at 33%, you get a terawatt with a million turbines, rather than 4 million.
You can find more in the Nature article I linked to above, and more still at David McKay’s excellent site (http://www.withouthotair.com/)
As various people have noticed, some interesting new patent filings from 2008 have just become public. They pretty clearly flow from brainstorming at a meeting of Intellectual Ventures, Nathan Myhrvold’s innovation [cornucopia|extortion racket] and deal with cooling the surface layers of the ocean by pumping warm surface water below the thermocline. The interesting thing to note is that as well as Nathan and various people who, following Gladwell, I think of as his regular crew — patent lawyer Casey Tegreene, Rod Hyde and Lowell Wood and some other Livermore people — the names on the patent applications include Ken Caldeira, John Latham, Stephen Salter and William H. Gates III. Ken (with whom, I should say as disclosure, I am actually working on something at the moment) is, along with David Keith and possibly Alan Robock, the academic researcher currently most associated with geoengineering discussions. John Latham has championed the possibility of cooling the earth by increasing the reflectivity of marine clouds, and his collaborator Stephen Salter has designed hardware that might do the job (their approach was the focus of my article in Nature this May, as well as many many more by other hands). You probably don’t need me to tell you who William H. Gates III is. He’s half the couple whose Foundation may end up having saved more people than were killed by Stalin, Hitler and Mao.
The main patent application, filed through a company called Searete LLC, describes something a bit like a floating paddling pool with a long pipe dangling down from its centre. Because there will be waves outside the pool but not inside, water will splash in over its edge but not out, and so the water level inside the pool is higher than the level outside the pool. (It strikes me that the motive force here might be treatable as a macroscopic analogue of the Casimir force, but I will leave that for Phil Ball to puzzle over.) That difference in levels — the head — does not have to be very large in order to overcome the buoyancy of the warm surface water and drive it down through the pipe to the cooler depths. Thus heat is taken out of the surface layers. Since high surface temperatures are crucial to the formation of hurricanes, a flotilla of such systems acting to cool potentially-hurricane forming waters in the mid-Atlantic might stop the hurricanes actually getting going, or divert hurricanes moving in from elsewhere.
Cooling surface waters to this end has been suggested before: a company called Atmocean has in fact built prototype systems which aim to do it in almost exactly the opposite way to the Searete patents, by using wave power to pump cool water up instead of sending warm water down. And as Atmocean and others have pointed out, if you can make such a system work there could be more global applications than stopping hurricanes. If you pump warm water down, you will be encouraging cold water to come up, and that cold water will contain nutrients. Lifting nutrients up from the dark depths to the lighter shallows is a way to encourage more photosynthetic growth. More photosynthetic growth might mean more net productivity — and thus more carbon dioxide turned into organic carbon and sequestered. In a 2007 correspondence in Nature, Jim Lovelock and Chris Rapley suggested that pumping up nutrients from the depths this way might be investigated as a geoengineering tool (here’s my blog entry on it from the time). And the Searete patent specifically covers just such geoengineering applications:
A system for altering an aqueous environment, comprising: an application of at least one vessel capable of moving water to lower depths in the water via wave induced downwelling; a system for determining the placement of the at least one vessel based on the application; and a system for placing the at least one vessel in the determined placement … wherein the application includes atmospheric modification … [and] climate modification.
For a fuller description not couched in the barbarous language of patent applications, have a look at Stephen Salter’s submission (pdf) to the recent National Academies panel on geoengineering. This work, which describes itself as funded by Intellectual Ventures, discusses a system 100m wide which has an array of one-way valves that let wave water in but not out, a more efficient and subtler way of doing things than just having some of the water slop over the top (though also one which carries the risks of having many moving parts). A typically neat Salter touch is to have it largely made out of used tyres and concrete. According to his calculations, one such piece of kit could transfer heat out of the surface ocean at a rate of 20GW, which is very impressive (though not in itself much of a match for hurricanes, which dissipate heat at a rate of tens or even hundreds of terawatts, I believe). He also discusses various ways that the hurricane-defusing pumps might encourage carbon-dioxide uptake. I was struck by a neat idea of Ken Caldeira’s: the system might be fine tuned to inject nutrients not into surface waters but into the bottom of the photic zone — the lowest waters at which photosynthesis is possible. It might be the case that increasing photosynthesis at deep levels like this, rather than at the surface as iron-fertilization experiments do, could have advantages in terms of the amount of biomass that ends up sequestered in the deeps.
None of this, I have to say, looks particularly practical or convincing. Jeff Masters at Wunderblog points to some generic problems with hurricane elimination/diversion/modification schemes — a raft of which, he points out, are under examination as part of a Department of Homeland Security project called HURRMIT, which grew out of this meeting in Colorado last year and in which Danny Rosenfeld, who also has an interest in geoengineering, seems to be playing a role. (Here are some associated subsequent presentations from a meeting of the American Meteorological Society). As Masters says, a major issue is that once you try and do something about a hurricane you may well end up getting sued for any damage that hurricane ends up doing, on the basis that if you hadn’t meddled the hurricane might have played out differently. And I suspect it would be very hard to show that such a system worked without trying it out at full scale, which is to say spending billions.
As for the geoengineering application, various people had cogent criticisms of the Lovelock and Rapley idea, including Peter Williams of Bangor and John Shepherd of Southampton, who chaired the Royal Society report on geoengineering heading off to the printers this week and being released in September. But this application does at least have the advantage of being testable on small scales in a way that hurricane diversion simply isn’t. David Karl and colleagues have already tried testing the Atmocean pumps to see if they can produce a double bloom of the sort that Karl’s theories about nitrogen availability would predict. The preliminary results were not very helpful, though: there wasn’t enough shiptime and the pump they deployed broke down:
The “keel” designed by Atmocean was structurally insufficient, and welds of reinforcing material around connection points were also insufficient…The single pump that was recovered showed multiple signs of failure, most notably the tarp tube system that was used…The couplers designed by Atmocean also proved to be insufficient in terms of strength and weld integrity.
In this respect I imagine the no-moving-parts approach described in the Myhrvold et al would be a significant improvement.
The most significant thing about the patent, though, at least for the moment, is not necessarily how good the system is at achieving various goals. It’s the appearance of Gates’s name, which may be his first public demonstration of an interest in geoengineering technologies. Such an interest is hardly a surprise: if you were spectacularly wealthy, concerned for human well being, technologically minded and had a track record of intervention on a world-historic scale, wouldn’t you be interested in at least looking at such technologies? For my part I don’t find that interest unwelcome, either. But I can see it is the sort of interest one could imagine wanting to keep quiet. Some of the many anxieties about geoengineering, after all, focus on what David Victor has called the “Greenfinger” scenario of the billionaire geoengineer going it alone, and this is the sort of thing that could stoke such fears. One to watch.
Filed under: Geoengineering, Global change, Interventions in the carbon/climate crisis, Published stuff
The last of my filling-in-for-Olivia columns at the NYT is now up, a quick run through some points from the later parts of Eating the Sun and subsequent stuff. It’s a carbon-climate crisis, energy is about flows not stocks, many wedges needed, yadda yadda yadda:
Given that humans are changing the atmosphere at an unprecedented rate, what responses should we expect from the biosphere? And is there anything that we can do to make those responses work to human benefit? For those in a hurry, the answers in brief: a) complicated ones; b) yes, at least a bit.