Geoengineering can take nearly any form; as the name implies, it's any engineering feat that affects a large portion of the planet. But in the context that it's used today, it almost always means an attempt to avert global warming.
For most of this idea's lifespan, it has been shudderingly viewed as a last-resort measure in case the environment begins to disintegrate around us (geoengineering may have first been conceived as a method for ending droughts or halting hurricanes). Any attempt to influence the planet on a massive scale could logically have terrible unforeseen consequences, on a similarly huge scale.
Now geoengineering is inching its way into the public imagination, as journalists, governments and even some scientists figure out ways of talking themselves into believing it's a pretty good idea. From this Monday's edition of the New York Times:
Today this approach goes by the slightly less grandiose name of climate engineering, and it is looking more practical. Several recent reviews of these ideas conclude that cooling the planet would be technically feasible and economically affordable.Most of the rest of the article is occupied by various geoengineering ideas, but The Atlantic already did a better job of painting the picture (figuratively and literally -- take a look at their cover art):
... if the climate does become dangerously warm, there could be enormous political pressure to do something quickly. And while it wouldn't be easy reaching international agreement on how to reset the planet's thermostat, in some ways it is less daunting than trying to negotiate a global carbon treaty.
If we were transported forward in time, to an Earth ravaged by catastrophic climate change, we might see long, delicate strands of fire hose stretching into the sky, like spaghetti, attached to zeppelins hovering 65,000 feet in the air. Factories on the ground would pump 10 kilos of sulfur dioxide up through those hoses every second. And at the top, the hoses would cough a sulfurous pall into the sky. At sunset on some parts of the planet, these puffs of aerosolized pollutant would glow a dramatic red, like the skies in Blade Runner...The Atlantic goes on to point out that one of the most dangerous details of climate engineering is its price -- almost any idea is cheaper than rebuilding the world's energy economy from low-carbon sources.
As it happens, that's the detail that is sweet honey to the legions of people who oppose any action on climate change, reasoning that it may affect local economies (nevermind that the jury is still out on how much affect any action would have). Bjorn Lomborg, a Danish activist who believes in climate change but would prefer not to spend much money on the problem, is the latest fan. He writes in a widely-distributed editorial:
World leaders are meeting in Copenhagen this December to forge a new pact to tackle global warming. Should they continue with plans to make carbon-cutting promises that are unlikely to be fulfilled? ... What could be achieved by planting more trees, cutting methane or reducing black soot emissions? Is it sensible to focus on a technological solution to warming? Or should we just adapt to a warmer world? ...Noting that Lomborg took his Ph.D. in political science -- rather than something remotely related to any form of engineering, much less one involving the whole planet -- could serve as an indictment. But Lomborg is also keenly attuned to political realities. He knows that politicians love nothing better than the easy way out.
It is remarkable to consider that we could cancel out this century's global warming with 1,900 unmanned ships spraying seawater mist into the air to thicken clouds. The total cost would be about US$9 billion and the benefits of preventing the temperature increase would add up to about US$20 trillion ... Many of the risks of climate engineering have been overstated.
Researching geoengineering is certainly responsible, but it's hard not to feel like we're being steadily drawn into the vortex of political expediency. With some notable personalities giving up on cap and trade, including its inventor, and most countries preferring a cheap policy of non-action, engineering the planet could turn from a scary last resort to the accepted future.
Nevermind the potential for creating the same unpredictable temperature swings and weather effects that global warming may someday bring about, with all their attendent affects (storms, starvation, and death on a large scale).
For more specifics on schemes, the The Atlantic article above is probably the best bet, but you can also read up on geoengineering in recent articles from the Wall Street Journal and Scientific American.