By Richard A. Lovett
Attempting to offset global warming by injecting sunlight-reflecting gases into the upper atmosphere isn't the quick fix for global climate change that advocates believe it might be, a new study finds.
In a paper published July 18 in Nature Geoscience, Kate Ricke, a climate physicist at Carnegie Mellon University in Pittsburgh, Pennsylvania, and her colleagues show, by modeling, that not only could solar-radiation management lead to declines in rainfall in the long term, but its effects will also vary by region. Some places will be over-cooled by atmospheric changes that are too small to be effective for their neighbors.
The gases under consideration are sulfur compounds that would produce sulfate aerosols in the upper atmosphere. Geoengineering advocates have proposed injecting large quantities of these materials into the stratosphere, either by shooting them up in artillery shells or releasing them from high-flying airplanes.
Once there, they would disperse into a thin, bright haze that would reflect enough sunlight back into space to partially or completely offset global warming.
The goal would be to mimic the effects of volcanoes eruptions such as the 1991 eruption of Mount Pinatubo in the Philippines, which blasted enough sulfates into the stratosphere to temporarily reduce the global temperature by nearly half a degree. Geoengineers propose mimicking this on ever-expanding scales, so that increasing levels of greenhouse gases are offset by ever-greater levels of sunlight reduction.
The new study found that it is fairly easy to design sulfate-injection scenarios that keep the temperature stable until 2080. But, unfortunately, the change in sunlight alters other weather patterns. "It changes the distribution of energy in the troposphere so that it becomes more convectively stable," Ricke says. The result: decreasing precipitation.
Temporary fix
Regional effects are also important. For example, Ricke says, her study found that levels of sulfate that kept China closest to its baseline climate were so high that they made India cold and wet. Those that were best for India caused China to overheat. She notes, however, that both countries fared better either way than under a no-geoengineering policy.
The modelers also found that all of these effects get worse with time. "The compensation is imperfect," Ricke says. "The longer you do it, the more imperfect it becomes."
Thus, she says, this type of geoengineering is at best a temporary fix--something people working in the field had always known because it does nothing to prevent the accumulation of carbon dioxide and the resulting acidification of the oceans. "But it might be even more temporary than people had expected."
Other scientists are impressed. "I think the paper is great," says Ken Caldeira, a climate scientist at the Carnegie Institution for Science's Department of Global Ecology, in Stanford, Calif. "I offered Kate a post-doc based on these results."
Alan Robock, a geophysicist at Rutgers University in New Brunswick, N.J., agrees. "It confirms that it is not possible to control both temperature and precipitation using stratospheric geoengineering," he says.
Cloud computing
The researchers used a global climate model, called HadCM3L, from the Hadley Centre for Climate Prediction and Research in Exeter, UK. To run their simulations, however, they made use of climateprediction.net, a climate-forecasting experiment in which thousands of people volunteer to have their home computers do climate simulations when inactive. "This is something that people can sign up for on home computers that sit idle most of the day," Caldeira says. "When the computer notices it is idle for a while, it starts running climate models."
Caldeira and Robock are impressed by the use of Climateprediction.net, but Caldeira points out that as the team only used one model, some of Ricke's specific findings, such as the details of the India-China disparity, might be model-specific.
"I don't think climate modeling is at the point where we should trust one single model at that scale," Caldeira says. "But I think the results are robust in the sense that it's the kind of issue that people will need to face. The qualitative idea is that you're going to have differential results in different regions, and that's going to cause people to want different amounts of this stuff up there, if they want any of it up there at all."
Ricke agrees. "We don't intend these results to give a definitive indication of what's going to happen," she says. "It's more an illustration of the type of regional effect you would see."
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16 Comments
Add CommentI agree. We are going to have to face what we have done with the air that keeps us ALIVE. But to add more chemicals? We need to think about decreasing the amount that is produced by us humans Adding more to solve the problem isn't the way to go. We need to change the way we live. No other way will work. Instead of blocking the Sun, we need to live with it. It produces ALL the power we will ever need. Need to make products with that in mind. All aspects of life for us relies on us doing just that.
Reply | Report Abuse | Link to thisHow long will the CO2 levels be elevated? That how long any 'temporary' compensatory method must effectively moderate the resulting conditions produced...
Reply | Report Abuse | Link to thisWhy is the screen saver distributed computation process mentioned as though it was some new development not invented around 30 years ago?
jtdwyer - because the author hadn't heard of it.
Reply | Report Abuse | Link to this30 years? I remember running setitathome starting about 12 years ago.
MikeInMaine - Yeah, about 30 years ago I might had read some article in an electronics engineering journals. Never used the stuff myself.
Reply | Report Abuse | Link to thisThe temptation to find balancing solutions is strong, but can we really forecast the full picture? We may create bigger problems. Another question to ponder is the relevance to other climate control / change programs (e.g. for Mars).
Reply | Report Abuse | Link to thisAmiram - Modification of complex systems often produce unexpected results, especially when expectations are based on evaluations of simplified analytical models.
Reply | Report Abuse | Link to this"injecting sunlight-reflecting gases". Why are we allowing these frighteningly stupid people even suggest that we inject anything into our atmosphere? Can't they see what injecting chemical gasses into our atmosphere has done so far? You can't pour gas on a gas burning fire and expect to put it out...it just makes it worse; even the idiots know that. We should never allow mentally-retarded people work as Climate Engineers.
Reply | Report Abuse | Link to thisA couple of the commenters here has the right idea...stop putting carbon monoxide into our atmosphere and we will not need sunlight-reflecting chemicals injected into our "Life-giving Air". I would rather inject electric cars and geothermal power plants into our atmosphere that some deadly chemical. There had better be someone with enough power to stop these stupid idiots before they kill us all.
They only suggest solutions they know will not be implemented for a variety of reasons, but primarily because they are science fiction not science fact. Its the same old arguement to maintain the status quo "More research is needed".
Reply | Report Abuse | Link to thisEven if this was feasible, to effectively simulate the effects of a really massive valcanic eruption every week, and even if the side effects were negligable (which they are not) it would be a bandaid fix, not a root cause fix.
Do we really want to commit ourselves to such a massive expense, far more than just rebuilding the grid to be green. Seriously, a giant euruption every week.. that's a lot of material to control.
Besides, we have better solutions that will actual fix the root cause, with the added benefit of modernizing our antiquate power delivery and transportation systems.
Look up at the skies. This has long passed the computer modelling stage..
Reply | Report Abuse | Link to thisThe best approach still looks to be that of directly removing carbon dioxide from the air. Klaus S. Lackner's suggestion in "Washing Carbon Out of the Air," on page 66 of the June "Scientific American" still looks practical.
Reply | Report Abuse | Link to thisHe admits that it takes energy, but there is plenty of free solar power in the southwest United States. It doesn't even have to be transmitted anywhere, as it does not matter where the carbon dioxide is removed.
Greenhouse gasses are the principal drivers of global warming, I agree. However human population numbers are the principal drivers of greenhouse gasses.
Reply | Report Abuse | Link to thisWhile I was doing my compulsory military service I can remember they added probably potassium bromide to our food to dampen our libido. Now we have plenty of ways to lower fertility, lets get on with it, though it does not matter if we do nothing.
Its too late to do anything about loss of landmass. Heat input has mainly gone to melting ice. It takes about 80 calories to convert 1 gram of ice from solid to water without any change in temperature, the same heat would heat 1 gram of water from 20C to 100C. The warming we observe is minimal now, but once the ice mass reduces those alive, at that time face disaster. Luckily it will not be any of us.
Sit back relax and let evolutionary processes do what they must. Evolution does not favour overly intelligent species, they always bring about their own extinction. Now you know why we have not been visited by intelligent aliens.
scientific earthling - Well said. If only we could minimize the future suffering of billions.
Reply | Report Abuse | Link to thisIf the inserted sulpher reflected the sun's direct rays from reaching the Earth, why would it not become another greenhouise gas blankering the sun's heat that did get through ?
Reply | Report Abuse | Link to thisPlants absorb CO2. Pyrolyse the plants and you get carbon and hydrogen. The carbon can be put in landfill, or the two elements used to producr biogas or biofuels. The technique is cheap and the pyrolysis units are available . There are hundreds of millions of vehicles in the world. With just five million pyrolysis units we could get rid of excess CO2 in the air and have a sustainable energy source. See : www.eprida.com
Reply | Report Abuse | Link to thisIs this what we in Holland call 'chemtrails'?
Reply | Report Abuse | Link to this"injecting sunlight-reflecting gases". Why are we allowing these mad scientists to even suggest that we inject anything into our atmosphere? To many $$ not enough cents (Sense). The sun is the life force for all life on earth.
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