This piece is reposted because an Op ed in today's NYTimes repeats its theme. It first appeared here in December of last year
Geo-Engineering happens. By 1751, Ben Franklin had noted how the Founding Fathers had changed our as yet unfounded nation's balance of solar energy. "By clearing America of woods and so making this side of our globe reflect a brighter light" Franklin noted , they had literally altered the Earth's albedo.
Ten generations later , the first Earth Day led to America's Clean Air Act and a ten million ton a year drop US sulfur dioxide emissions. This, as inadvertently as in 1751, unexpectedly contributed to global warming by letting more light penetrate the atmosphere. The two satellite photos shown here demonstrate an important corollary --bouncing more sunlight back into space can cool the Earth.
Today , this phenomenon is the subject of a review of atmospheric albedo engineering in Nature.[subscription required]
Though alteration of the Earth's radiative equilibrium can happen by accident or design, those most viscerally opposed to geo-engineering often have designs of their own.The thoughtful Nature piece does much to correct naysaying by carbon traders and others with political agendas. It notes how radically the deposition of solar warmth can be altered by very small masses of aerosols. The equivalent of a few pound per capita of fine mist from the 1992 eruption of Mount Pinatubo scattered enough sunlight back into space to cool the planet more than CO2 build-up had warmed it in the previous decade . The cooling glare startled sunset watchers for a year. And fired the tempers of self-appointed ethicists who prefer societal intervention to dealing with climate change directly.
Experience teaches that a little mass can cast a lot of shade. A few tons of jet fuel can lay a sun-reflecting contrail from coast to coast. A chilling corollary dawned on Nobel laureate Paul Crutzen a decade ago, and now he has floated the notion of
aircraft delibeerately generate stratospheric sulfur aerosols to stop global warming cold. "It was meant to startle the policymakers," says Crutzen. "If they don't take action much more strongly than they have in the past, then in the end we have to do experiments like this."
Dr. Crutzen's attempt to find a place at the table for unorthodox ideas comes not a moment too soon. Intellectual daring doesn't figure in Olympia Snowe or Al Gore's attacks on those who insist the debate is not over, but Crutzen is hardly alone. In the Washington Post, Robert Samuelson has pointed to the folly of mistaking global warming for "a moral crusade when it's really an engineering problem. The inconvenient truth is that if we don't solve the engineering problem, we're helpless."
The truth that sets the IPCC free may not be the one its political
managers want to hear - but that has not prevented the horde of authors
from leaving it out in plain sight .The new report's section on climate
sensitivity notes that "Clouds, which cover about
60% of the Earth’s surface, are responsible for up to two-thirds of the
planetary albedo, which is about 30%. An albedo decrease of only 1%,
bringing Earth’s albedo from 30% to 29%, would cause an increase in the
black-body radiative equilibrium temperature of about 1°C, a highly
significant value, roughly equivalent to the direct radiative effect of
a doubling of atmospheric CO2 concentration."
And a 1% increase in albedo , say the same atmospheric computer models the global warming worriers invoke , would lower the Earth's average temperature by about as much as the IPCC predicts it will rise in the century to come . Turning a few pounds of sulfur per capita per year globally into cloud cover enhancing aerosols or condensation nuclei could , quite conceivably accomplish that. In some decades, major volcanic eruptions naturally inject far more sulfur , so it is hardly a concept outside the bounds of the natural history of climate . It be enough to arrest the melting of the polar ice caps. Such an aerosol arctic sunbonnet might cost roughly as much as the power bill for running the Internet. Little wonder, then, that Mr. Gore and his communitarian cohort are aghast. Such modest post-modern proposals threaten to cut their fantasies of Deep Green societal control -- and moral superiority -- down to economic size."
Crutzen's proposed solution has little to do with pollution. Smokestack emissions in the lower atomosphere are too short lived to provide economic leverage on fighting global warming. Engineered aersols put far higher in the sky- in the lower stratosphere in fact , ar the focus of his interest. He also notes that they can do a lot more good at high latitudes , because slanting rays of sunlight interact with more particles than the vertical rays of the tropical sun. The story of this policy paradox began a decade before I first met Crutzen at a 'nuclear winter' conference in Sicliy in 1984.
Responding to the ’Energy Crisis.’ of the ’70’s the National
Academy of Science identified coal and conservation as bulwarks against
OPEC oil blackmail, but proposals to conserve fuel collided with a
democratic Congress anxious to reduce acid rain. In terms of energy
efficiency, draconian reductions in sulfur emissions- a legislative
move spearheaded by hearings held by freshman congressman Gore,
backfired badly . Rather than investing in more efficient combustion
technology; industry bought SO2 scrubbers instead. They literally put a
damper on combustion, and instead of climbing, average US power plant efficiency fell for a
decade despite advances in high temperature materials that made for more efficient jet
and car engines. Regulation also forced a massive shift from burning
electrical coal close to eastern mines to stripping and shipping
low-sulfur fuel from the prairies of Wyoming. Nonetheless, by 1990 the
Greens got they asked for - a solution to the problem of acid rain
purchased at a high cost in carbon dioxide.
Meanwhile science was learning a lot about what it did not know. One fact of natural history is that a relatively small mass can cast a great deal of shade. Combusting just tons of jet fuel can transiently cast a mile wide sun reflecting contrail from coast to coast. The absence of such clouds in the days after 9-11 changed ground temperatures measurably, and the fallout from that observation includes the idea that long lived clouds generated far aloft might offset the warming effect of CO2 in the air. Contrail water clouds dissipate in minutes, but sulfate motes can last for months- hence the cooling from stratospheric volcanic eruptions like Mount Pinatubo in 1993, or as Ben Franklin also notes Iceland’s Mount Hekla in the 18th century .can lessen global temperatures for a year or more. And just as a long lived mist of sulfur rich volcanic droplets can palpably intercept the heat of the sun, so can one from burning fossil fuel.
One reason the Kyoto treaty crashed and burned was that economists who did the math discovered it could pare scarcely a tenth of a degree off 21st century temperatures. That’s where the Law of Unintended Consequences comes in. The last thing Earth Day’s instigators had in mind in 1970 was warming the planet, but being clueless to how much cooling ten million tons of sulfate aerosol could cause , Clean Air Act advocates literally could not conceive that inventing the EPA could have a negative environmental impact, let alone that sulfur burned to no good effect could instead furnish shade sufficient to slow the melting of polar ice . Yet they are hoist on their own petard - it is now clear that curbing sulfur emissions exacerbated the rise due to CO2.
Perhaps PBS should produce a NOVA episoe on the subject, cataloging the ways that unbridled legislative zeal may lead to a frozen planet, with New York Harbor left high and dry as sea levels recede. It would make a great vehicle for the narrative skills of one of my Harvard classmates, an unemployed politician from Tennessee. If agents in the audience want to discuss my new script proposal, its working title, copyright 2006, is The Day Before Yesterday.
Further reading :
- Crutzen, P. J. Climatic Change 77, 211–220 (2006).
- Wigley, T. M. L. Science 314, 452–454 (2006).
- Ocean acidification due to increasing atmospheric carbon dioxide. Royal Society policy document 12/05 (2005).
- Govindasamy, B. & Caldeira, K. Geophys. Res. Lett. 27, 2141–2144 (2000).
- Oman, L. et al. Geophys. Res. Lett. 33, L18711 (2006