ON SCIENCE
Sharon Begley
The ‘Geo-Engineering’ Scenario
Why even a desperate measure is starting to look reasonable.
After decades spent studying volcanoes, Alan Robock can list 20 reasons why humans should not try to play God with the world's climate by, well, mimicking Krakatoa. Proponents of "geo-engineering" actually like the idea because the eruptions spread sulfate aerosols and other particles throughout the planet's atmosphere, reflecting incoming sunlight. The resulting cooling might counter the global warming caused by carbon dioxide and other greenhouse gases. But that's not all sulfates do, which is where Robock's list comes in.
The particles also deplete the planet's ozone layer, which is just starting to repair itself now that ozone-shredding chemicals are banned. They cause acid rain, too. And by cooling large land masses like Asia and Africa, the heat-reflecting particles reduce the temperature difference between them and the already-cooler oceans, which could stifle the monsoons that millions of people depend on for agriculture. Because the particles block direct sunlight more than diffuse rays, they also alter the balance of radiation reaching Earth's surface, with unknown consequences for plants that can be kind of finicky about the kind of sunlight they need.
And yet … In a sign of how dangerous global warming is starting to look and of how pitiful the world's efforts to control greenhouse gases are, even Robock—list and all—hedges his bets. Geo-engineering, allows the Rutgers University meteorologist, "might be held in reserve for an emergency."
The prospect of a climate emergency has put geo-engineering, which experts have been weighing since at least 1992, on the drawing board more than ever before. That reflects two alarming developments. The first is that some projections of climate change, far from being Cassandra-ish, are turning out to be too conservative. According to satellite measurements, sea levels rose 3.3 millimeters per year from 1993 to 2006; the Intergovernmental Panel on Climate Change had projected less than 2 millimeters. Also, the IPCC projected loss of arctic sea ice at 2.5 percent per decade from 1953 to 2006. It's actually been 7.8 percent, or 30 years ahead of projections. Greenland's ice sheets, too, are melting faster than expected. If other consequences of climate change—heat waves, storms and severe droughts like the one now gripping the southeast—also turn out to be worse than projected, the world may become desperate for a way to turn down the thermostat much faster than reducing CO2 emissions can accomplish. (Especially since emissions are trending the wrong way. In the 1990s, they increased 1 percent a year. In the early 2000s, 3 percent a year.)
The physics of geo-engineering is not in dispute. Studies of volcanoes established what amount of particles produces how much cooling, as well as how the particles spread and how long they remain aloft (a year or two). Knowing this, it should be possible to roll back the global warming projected for 2100 enough to return the planet to its climate of 1900, Damon Matthews and Ken Caldeira of the Carnegie Institution reported in June.
The devil, however, is in the details. Injecting sulfates into the atmosphere—by lofting big, aerosol-filled balloons or rockets—would reduce global precipitation to below the levels of 1900, their study showed, threatening agriculture. Cooling would be uneven, with some regions benefiting more than others. (What would Russia, which might benefit from global warming, do if India, which would suffer, decided to cool things down through geo-engineering?) And if the world stopped geo-engineering and therefore unmasked the effects of CO2 that had been accumulating all along, the effect could be calamitous, as temperatures shot up 20 times faster than current warming, notes Matthews. That would be harder to adapt to than an equal rise spread over more time.
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Member Comments
Posted By: infracanis @ 01/18/2008 8:13:44 PM
Comment: These comments offer very little in constructive thought. I thought the title is a little misleading as far as the viability of geo-engineering. The even propostion of these ideas postpones action possible until too late. As well, it detracts from concentrating on an economic transition to ecologically sound consumption. CO2's greenhouse effects are scientically documented. To deny the possibility of human-caused climate change is to deny our own scientific and technological basis of culture. This crisis will absolve the ignorance and prejudice within modern society to reveal inherent opportunities of Man's station. "The Earth is but one country and mankind its citizens' as a great man once said and I believe that.
Posted By: William.Demuth @ 12/07/2007 9:20:45 AM
Comment: Hello! Get a grip people. First of all significant C02 emissions are caused by humans. More humans, more C02 and the planet heats up. Want the planet to cool down, stop breeding like roaches! Stop the political correctness for a second and take a REAL look at the issue, and you will see it is not our technologies that cause the imbalances, it is our population. Whatever draconian steps we can imagine will have zero cumulative impact if we keep growing the human infection on this planet. Our relationship with the ball of dust we call home has been symbiotic for centuries, but we are increasingly parasitic. But don't worry to much, you couldn't wipe out the human race if you tried. We make rats seem like a non invasive species. All that will happen is we will adapt. Sure millions or even billions will die, but nowhere near enough to wipe us out. You see we are the problem, and any attempt to resolve it would be like roaches discussing how best to divide a loaf of bread. If we reduce our footprint by half, and double our population, we are actually worse off than when we started. If we will not willingly reduce our population, good old mother nature will do it for us! As for me, I own a nice piece of land in New Jersey that's 28 feet above sea level, and I figure it will be ocean front by the time I die! As for those who want to take from me financially to feed this con game I have some bad news for you. Anytime anyone tries to impact my standard of living to avert global warming I will simply add another log to my fireplace and laugh.
Posted By: euggordon @ 12/06/2007 4:55:22 PM
Comment: The science of global warming is not science but opinion, often not well informed, and probably motivated by self interest. It is highly likely that the only science is related to how sunspots influence the global average surface temperature, through varying the amount of warming solar radiation incident on the Earth and the varying the average cloud cover acting as as an umbrella.. However, if there is concern about how global warming should be controlled it relates not only to manmade CO2 but as well togeoengineering. Control of the amount of solar energy reaching the Earth by injecting sulphates is well known and Sharon Bigley does a good job of outlining the pros and cons. Unfortunately there are serious cons and experiments should be done with great care. However, there are better thermostatic mechanisms that would do the job without risk. Last year Roger Angel described one such to the National Academy of Science. It involves putting into stable orbit at the Lagrange point between the Earth-moon system and the sun 900,000 miles out an array of umbrellsas that would partially shield the Earth from sunlight. The system would pose no risk to the Earth, would cost far less to implement than Kyoto, would take far less time and would allow good control of the Earth's average surface temperature for 50 years. If anyone is really seiious about doing someting about global warming the ideal solution is available. The fact that you hear nothing about it gives the lie to the so called global warming scientists who are pushing manmade CO2 reduction as the solution. Space umbrellas are by far the cheaper, safer, quicker and more certain solution, without negative consequences. Why are we not doing it? Ask the global warming community. Be warned. They won't comment because it undermines their position.