SHIP TRACKS: Could ships spraying sea mist to boost cloud reflectivity cure climate change? Already, ship tracks can be picked out in marine clouds, as pictured here, thanks to the interaction of ships' exhaust and water vapor in the atmosphere.
Image: Courtesy NASA/GSFC/LaRC/JPL, MISR Team.
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Here's an idea to cool Earth: make marine clouds into better reflectors of sunlight. After all, clouds already reflect more of the sun's radiation back into space than the amount trapped by human emissions of carbon dioxide. So why not make them even more effective?
Enter "marine cloud brightening," a geoengineering scheme that would increase cloud reflectivity over the ocean by spraying them with an ultrafine saltwater mist from ships. The clouds, containing more particles, would cast enough sunlight back into space to at least partially offset the warming effects of all that CO2 from burning fossil fuels.
Climate scientists have mixed reactions to the idea, which was first proposed in 1999 by climatologist Jonathan Latham of the National Center for Atmospheric Research in Boulder, Colo. For instance, Andy Jones and colleagues at the Hadley Center for Climate Prediction and Research, Met Office in the U.K. think that if marine cloud brightening were deployed in the Atlantic Ocean, it might help turn the Amazon rainforest into a desert by cooling the South Atlantic, which would lead to less evaporation from the ocean, thus reducing rainfall over the forest. A new study however, has found that marine cloud brightening would enhance rainfall over land, counters Latham, who did not want to identify the authors because the paper has yet to be published.
Nevertheless, a growing number of engineers have already begun to think about how marine cloud brightening could actually be accomplished. A handful of obstacles to the realization of Latham's vision have been identified, chief among them the problem of creating hundreds of gallons per minute of sea spray, but the engineers involved are optimistic.
How "albedo yachts" could work
Stephen Salter, an emeritus professor of engineering design at the University of Edinburgh is the lead and was for many years the only engineer working on a proposal to accomplish marine cloud brightening by populating the world's oceans with up to 1,500 ships of a somewhat exotic design—sometimes known as "albedo yachts". Each vessel would be remote-controlled, wind-powered, and capable of generating (via turbines dragged through the water) the electricity required to create a mist of seawater and loft it 1,000 meters into the atmosphere.
Instead of using sails, Salter's ships would transform wind energy into thrust via the use of Flettner rotors. First used on a ship in 1926, Flettner rotors consist of spinning tubes resembling oversize masts on a conventional sailing vessel. The tubes interact with wind in much the same way the wing of an airplane does, generating "lift" perpendicular to the axis of their rotation. Flettner rotors are a proved, if rarely used, technology because they were not invented until the twilight of wind-powered shipping, when propellers and fossil fuels became the propulsion mechanism of choice. Salter chose them, however, because they can be powered by a renewable resource, they're easy to control with an onboard computer, they're better in hurricane winds than conventional sails—very necessary for an unmanned craft wandering the seas for years—and they provide a natural place to house the vessel's seawater spraying system.
"Although they look so science fictiony, those Flettner vessels, they also, I think, have a high chance of being suitable vehicles for this job," Latham says. Salter estimates that if the world completely fails to curtail CO2 emissions, his scheme would require a fleet of up to 1,500 vessels, which would have to be deployed at the rate of about 50 a year in order to keep up with increasing atmospheric carbon dioxide. The construction alone of all 1,500 vessels would cost between $3.2 billion and $4.8 billion, with unknown and uncalculated maintenance costs or even the crafts' lifetimes.
The challenge of micron-size droplets
Ultimately, to counteract the effects of a doubling of the amount of carbon dioxide in the atmosphere from preindustrial levels, Salter estimates that each of the 1,500 ships must do something no one has ever attempted—transform 30 liters of seawater per second into a uniform spray of micron-size droplets.
According to Latham's calculations, the saltwater droplets sprayed into the atmosphere must be between 0.8 and two microns across. (For reference, two microns is about the size of an Escherichia coli bacterium.) Latham's work also suggests the droplets should all be the same size so that they don't clump together and form larger drops, which could cause clouds above the ship to drop rain and dissipate—the opposite of the intended effect.
"Trying to make these droplets is really the crucial part, and it remains to be seen if it's going to work," says Armand Neukermans, an engineer and serial entrepreneur who is attempting to lead the U.S.-based effort to create a suitable spray system. Neukermans, a veteran of Xerox and Hewlett–Packard, has gathered a team of a dozen engineers who, like him, have expertise in creating micron-size particles for printing and micro-fabrication. The group includes John Vaught, who was the primary inventor of thermal inkjet printing while at HP. Many of the group's members are semi-retired, and all are working on a mostly volunteer basis.
"We're the plumbers," Neukermans says. "It's an eclectic group."
Back to silicon chips
Edinburgh's Salter, for his part, has tested and discarded a number of ideas about how to create the spray, including collisions between two air-saturated jets of water, which make them more likely to explode into tiny droplets; vibrating piezoelectric vaporizers of the kind used for theatrical effects; and a unique machine of Salter's own devising that he describes as the hydraulic equivalent of a photomultiplier—it would consist of a series of electrically charged plates to create an ever-expanding cascade of droplets. Ultimately, astrophysicist Lowell Wood, an early advocate of geoengineering, suggested that Salter could simply force water through an array of tiny holes, like a watering can. Making that work will require drilling 1.5 billion holes 0.8 micron in diameter in a single 20-centimeter-diameter wafer of silicon. (Silicon was the obvious choice for this solution because chip-fabricators have decades of experience in creating very tiny devices with it.)
Tom Stephenson, a collaborator of Salter's who is operations director of the Scottish Microelectronics Center at the University of Edinburgh, has etched comparable shapes into silicon before, such as tiny holes for use in optical pressure sensors, and believes it would be feasible to create, with conventional chip-fabrication technology, the billions of holes required.
"What's not clear is how well silicon wafers will withstand the pressure, and it's not sure how good it will be in presence of defects such as a nick in [the] edge of a hole," Stephenson says. "Silicon, being a crystalline material, has a tendency to fracture along fault lines and crystal planes."
Neukermans and his team have conducted "very preliminary" experiments with seawater forced through micron-size holes, and the initial results have not been encouraging. Using seawater that has been "polished," or filtered many times, Neukermans has tested holes from 25 microns down to one micron.
"A 25-micron hole you can keep open forever," Neukermans says, "but a five-micron hole is a lot of trouble, and a one-micron hole is a hell of a lot of trouble. With a one-micron hole, only two droplets will go through before it clogs." Neukermans does not know why the holes are clogging or even what is blocking them, and he emphasizes that further experiments are required.
Salter's spray system design anticipates the issue of clogging—he hopes to solve it by back-flushing his micron-size holes with more water—but what's required now is actual testing of his elaborate designs. That's going to require funding, which has been scarce because the entire field of geoengineering remains suspect to many climate scientists and, until very recently, to scientific funding bodies. The first batch of funding specifically earmarked for geoengineering was announced in September by the Research Council UK's Energy Programme, but it is unclear yet what the scope of this funding will be.
"You can go an awfully long way with brain power and access to the right library," Salter says, "but it's getting to the stage where I can't do very much more."
What about using conventional ships?
But where national science funding sources have failed, Silicon Valley entrepreneurs have stepped in, investing small amounts of money as a philanthropic enterprise—the total is undisclosed, but it includes the Salter's travel expenses—to explore the potential of geoengineering.
"The work we have done, which is not very extensive, is probably a large fraction of geoengineering funding in the world," says Nathan Myhrvold, former Chief Technology Office of Microsoft, founder of Microsoft Research and current head of Intellectual Ventures, a company whose primary product is patents on ideas generated in closed-door brainstorming sessions. When asked whether Latham's and Salter's geoengineering schemes are practical from an engineering perspective, Myhrvold responds that he believes it’s practical, but that "All of these [geoengineering] ideas need a lot more work. Stephen [Salter] and John [Latham] would be the first to say that. I think it needs to be followed up."
Myhrvold points out, however, that Salter's "very elegant" ships with rotating sails are not the only way to accomplish Latham's geoengineering plan. "Why not just put this [spray system] on conventional ships and use a diesel pump?"
Salter and Latham both agree that the next step for evaluation of this scheme by climatologists—large-scale field trials—could use ships of conventional design. And although none of the scientists involved advocates for the deployment of a geoengineering fix right now, they are eager to test and model its potential impacts so that if the world decides it is needed, its consequences are at least known.
"The climate problem is a very difficult problem for mankind," Myhrvold adds. "It's almost perfectly designed to evade our normal policy guidelines. We may need to bridge the gap between the time when we get to a renewable energy infrastructure and where we are today."
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25 Comments
Add Comment"Here's an idea to cool Earth: make marine clouds into better reflectors of sunlight."
Reply | Report Abuse | Link to thisHere's an idea: Stop putting greenshouse gasses in the air and you wont have to worry about what else to put in the air to counter balance the gluttony.
Calculation needed -- how much faster is CO2 going to dissolve in the oceans, with these devices operating?
Reply | Report Abuse | Link to thisQuestion -- why not make each ship a trough-type solar collector and superheat the ocean water under pressure then vent it as superheated steam at altitude?
Question -- remember the problems with the new-type "cool mist" home vaporizers putting lots of bacteria into the air?
http://scholar.google.com/scholar?q=cool+mist+vaporizer+bacteria
This seems to be reinventing that particular problem in large.
For a thorough rundown of all the climate aspects of this geoengineering scheme, SciAm's sister publication Nature News has a feature by Oliver Morton, Nature's then news editor:
Reply | Report Abuse | Link to thishttp://www.nature.com/news/2009/090429/full/4581097a.html
@agenthucky: You're absolutely right. Geoengineering should carry an "in emergency, break glass" type warning, and is not a substitute for CO2 mitigation.
@hankroberts: Can't answer your first two questions, but the third one might be answered by the fact that the seawater sprayed by these ships would have to be run through an extremely fine filter first, anyway. (Fine enough to remove even bacteria.) Unfortunately there wasn't enough space in this article to get into the proposed filtration system.
Planet Green channel's "Project Earth" aired an episode of this months ago. Rather than make the clouds more reflective, however, they simply tried to make more clouds. The colliding jet streams was ineffective, making particles that were too large. They succeeded finally by vaporizing water with rockets...hardly carbon neutral, but the concept worked. The Flettner rotors actually worked too, but are most likely too slow to be able to generate power with turbines dragged underwater. They used a fuel-powered engine, which makes it seem pointless to invest so much into the rotor system over a traditional diesel engine.
Reply | Report Abuse | Link to this1 will get you 10 that "geo engineering" will only screw us worse.
Reply | Report Abuse | Link to thisAbsolutely. The problem with every any sort of "geo engineering" is you're committing the human race to doing it for at least 100 years and possibly 1000 years at an unknown cost.
Reply | Report Abuse | Link to thishttp://www.realclimate.org/index.php/archives/2009/10/why-levitt-and-dubner-like-geo-engineering-and-why-they-are-wrong/
Just punish the polluters and make them stop putting so much crap into our oceans and atmosphere. Combating global warming is not going to be done with a quick fix. It'll be a hard slog at first, but that's better than having a hard slog for an unknown number of generations. And the (technological and scientific) benefits we'll get from getting it "right" will far outweigh those costs.
@Catharz - Of course we should stop polluting the atmosphere with CO2. But what if we can't make the switch to non-polluting energy sources fast enough. Do you really want to live in a world that's 4 deg C warmer than today with no options for cooling the planet at all? Renewables are 0.5% of the energy mix in the U.S. currently. Will we get to zero emissions in time? Let's hope so. But no scientist would even be looking at geoengineering as a supplement to carbon mitigation unless they were convinced that, given the scale of the problem, mitigation by itself is unlikely to work.
Reply | Report Abuse | Link to thisOf course I don't want to live in a world that's 4 deg C warmer. Even a 2C difference will kill our coral reefs, causing permanent damage to our ecosystems. We're already seeing significant damage occurring at 0.75C, along with other serious side-effects (like the ferocious bush fires experienced in Australia earlier this year). But I also don't want to pass on an expensive legacy to dozens (if not hundreds) of generations that follow.
Reply | Report Abuse | Link to thisGeo-engineering is less proven and a lot more dangerous than geo-sequestration. If we go the geo-engineering route, every country in the world will have to agree to it, spend money on it and continue to spend money on it for an indefinite period of time. If we started and subsequently stopped doing it in the future (for any reason), we'd find ourselves in a substantially worse position than we are in now. It'd be morally bankrupt for us to rely on it as a solution.
The only 100% sure fix is to reduce our production of CO2 to sustainable levels. Geo-engineering might be able to extend the window of time we have to do this. But any attempt to rely on it is absolute folly.
And scientists have been known to research and say anything if provided enough money. Singer and his ilk have repeatedly proven that.
@Catharz - I think you and I agree on all basic points save one: it's not about whether we'll do CO2 mitigation *or* geoengineering. The whole point is that we might be forced to do *both* - and in that case, the geoengineering lasts only until we can get CO2 levels in the atmosphere back down to reasonable levels. Will that take a 50 years? A thousand? No one knows.
Reply | Report Abuse | Link to thisBut I agree with you on this point - anyone who proposes doing geoengineering *instead* of CO2 mitigation is, at this point in the evolution of the technology, either uninformed, a wild-eyed optimist, or the worst kind of cynic.
Scientific American has become a joke when "Human Global Warming" is concerned. Of course the CO2 content is increasing, but there's absolutely NO evidence that it's a cause of global warming rather then an effect.
Reply | Report Abuse | Link to thisHere is just a bit less crazy idea:
Reply | Report Abuse | Link to thisConvert the Sahara desert into a green land by
building a salt water channel network (gets water from the sea)
and grow salt water tolerant plants all over.
Love it! Long words, fancy formulas and short on thinking...Our world has been getting ever so slightly warmer for over a 100 years, with a decade or so cooler temperatures, and guess what! It's natural!!! Are WE so arrogant as to think that WE control nature? Well, I guess some are, if the price is right!
Reply | Report Abuse | Link to thisSpiff
Reply | Report Abuse | Link to thisThese guys certainly are not sailboat designers!! Flettner rotors!! You got to be kidding. They have been tried and do NOT do storms well, generally getting demasted in high winds.
By far better would be catamarans with solid airfoils that dynamically adjust to the wind direction, far more eff, lighter, smaller and easily faired for storms with control tabs. Something like the Planesail concept of yrs past. I designed similar units to make H2/O2 but would easily adapt to water spray.
Next why would one use electric power when you can just use the shaft power to pump, avoiding the conversion losses of 30% or so. That means you can use a 30% smaller ship!!
Next to make the droplets, just blow air through the holes that a sheet of water flows past. No clogging and lower energy needs thus more output, 30% smaller ship/output again. And not using Flettner rotors one does need power to turn them, saving more.
The solution does not address ocean acidification, even if it worked to slow or stop global warming.
Reply | Report Abuse | Link to thisAcidification will kill the organisms that have a significant role in cloud formation and almost all sealife visible to the human eye. At the rate CO2 is being added to the atmosphere, the oceans will be sterile in as little as 20 years, i.e., there will be no seafood by anybody's definition to eat. Remember acid rain and what it has done to the forests and lakes downwind from coal fired electric plants.
AS James Lovelock wrote in The Revenge of Gaia, the actions that will work are: 1. stop burning fossil fuels, 2. stop destroying vegetation, 3. plant trees. He said that people will make attempts such as the scheme proposed in this article but they won't work. He predicts that the human population will decline to less than one billion no later than the end of this century if the are any of us left.
For those who have stated there is no evidence CO2 does anything, check this video which at 1:30 shows a thermal camera (similar to how the "Predator" alien sees the world ;-) trying to "see" a candle's heat energy through a glass tube as the glass tube is gradually filled with Co2. Now you see it, now you don't.
Reply | Report Abuse | Link to thishttp://www.youtube.com/watch?v=D6Un69RMNSw&feature=related
As for Geoengineering:
1. I agree that we should FIRST massively accelerate our shift into renewables.
And, only if we HAVE to, build 3rd and 4th Gen nuclear (that EATS all the nasty nuclear waste and nuclear warheads we've generated so far!).
2. Build ecocities and New Urbanism that require less energy in the first place. Current suburban designs are the most energy intense city forms ever invented. They could be transformed into trendier, more humane, less car intensive places to live by the New Urbanists. "Dense and diverse" should be our motto.
3. My FAVOURITE Geoengineering is Biochar. Cook up agricultural and local council biowaste, get syngas for fuel, and bury the charcoal. It improves the soil, buries carbon for thousands of years where it will do us some good, generates carbon credits for farmers, and...
"Lietaer said that a land mass the size of France using this system could lock up all the carbon the world needs to.”"
http://transitionculture.org/2006/01/18/eprida-too-good-to-be-true/
Ooooh, I hate to enter into this no man's land but for what it's worth, ultrasonic reed "whistles" have been around for many decades and make predictably sized aerosols. The texts are probably still around somewhere. :-}
Reply | Report Abuse | Link to thisOoooh, I hate to enter into this no man's land but for what it's worth, ultrasonic reed "whistles" have been around for many decades and make predictably sized aerosols. The texts are probably still around somewhere. :-}
Reply | Report Abuse | Link to thisHow about Green Sahara - quick, easy and chep way to capture carbon back to biomass.
Reply | Report Abuse | Link to thisAnd a quick way to stop the threatening runaway greenhouse effects...
Some 10 000 m3/second water from Kongo, Nile, etc rivers could make miracles in Chad basin - at modest costs.
Sahara has been during last thousands- millions of years mostly covered by big lakes and dense vegetation.
Green Sahara holds vast amount of carbon: about 10 miljon km2 forests, lakes, swamps, ...
If there is on average 100 kg of biomass per m2 , then there about 2000 000 m * 5000 000 m* 0.1 ton/m2 or 1 trillion tons of carbon in the Green Sahara. This about the same as the carbon now in the atmosphere?
But how to get enough water there at reasonable costs?
By damming Oubangui- river alone and letting 1000 m3/sec of river water flow to Lake Chad, costs are few hundred million bugs .
See:
http://en.wikipedia.org/wiki/Lake_Chad
http://lakechad.iwlearn.org/
ABUJA DECLARATION ON LAKE CHAD BASIN 2007:
"....positive impact of the proposed Oubangui-Lake Chad Water Transfer project and the fact that the project will serve as an opportunity to rebuild the ecosystem, rehabilitate and replenish the lake in a manner that will increase and improve the level of irrigation activities thus boosting agricultural production and reforestation...."
http://lakechadparlcomm.org/index.php?option=com_content&task=view&id=33&Itemid=48
Kai, a geologist
.. Green Sahara..
Reply | Report Abuse | Link to thisOil companies, like Shell, Neste Oil, BP,.. could have a big positive role here in turning Sahara green again ?
They should be allowed to burmn fossil fuels- if they help somewhere capturing carbon away from atmosphere.. ?
We are sliding into at least a Little Ice Age for the basic reason that the greenhouse gas CO2 is only a trace gas in the atmosphere and if it tripes or quadruples it is still a trace gas and only a trivial component of climate change.
Reply | Report Abuse | Link to thisBut don't believe me on this, just wait, watch, and learn what the next three winters have to teach us. Afterwards, American academia needs an overhaul. Doctors and lawyers have malpractice hanging over their heads--more scientists need to have the same sanctions hanging over their heads when they get mouthy, arrogant, and start throwing their weight around, crushing innocent people economically who were and are not ruining the planet at all.
Old Indian Trick:
Reply | Report Abuse | Link to thisWhen you discover you're in a hole, stop digging.
Old Indian Trick:
Reply | Report Abuse | Link to thisWhen you discover you're in a hole, stop digging.
As an adjunct to trying out new technology and CO2 generation mitigation, why not use existing desalinization technology and build plants at the margins of the world's great deserts bordering the oceans, such as the Arabian desert or the Sahara or the Australian desert and pump water into the interior and turn nonproductive land into carbon reduction forests or even food-producing cultivated land, a project which would also have the effect of lowering sea levels as the Greenland and Antarctic ice sheets shed their ice? Similar in scale and feasibility to the US, Soviet, and Chinese dam projects of the twentieth century? Also promote such ideas as diverting sea water into lakes or seas such as the Dead Sea basin or the California or Mexican deserts which would have a similar sea level rise mitigating effect.
Reply | Report Abuse | Link to thisAs an adjunct to trying out new technology and CO2 generation mitigation, why not use existing desalinization technology and build plants at the margins of the world's great deserts bordering the oceans, such as the Arabian desert or the Sahara or the Australian desert and pump water into the interior and turn nonproductive land into carbon reduction forests or even food-producing cultivated land, a project which would also have the effect of lowering sea levels as the Greenland and Antarctic ice sheets shed their ice? Similar in scale and feasibility to the US, Soviet, and Chinese dam projects of the twentieth century? Also promote such ideas as diverting sea water into lakes or seas such as the Dead Sea basin or the California or Mexican deserts which would have a similar sea level rise mitigating effect.
Reply | Report Abuse | Link to thisWhether the "Global Warming" is man made or not, does not bother me that much. Much worse is the situation on fresh water. The spray ship idea can be combined with moistening the air in the horse latitudes. If done when wind blows into the land, then more rain will fall in the deserts.
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