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The Cheapest Way to Fight Climate Change? Block Out the Sun

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This summer, the volume and extent of arctic sea ice fell to the lowest level on record; America experienced one of the hottest seasons in the last century; and the United Nations issued warnings about a coming world food crisis that could be catastrophic for tens of millions of people across the globe. All this, argues Bill McKibben, the patron saint of environmental soothsaying, is the New Normal.

So what’s a world to do as we get increasingly hotter, more extreme weather events? Block out the sun, of course.

Geoenginnering is the strange, far-from-perfect, science of deliberately intervening in the earth’s climate on a massive scale in order to mitigate the effects of climate change. One strategy, known as Solar Radiation Management, involves inserting debris into the atmosphere in order to reflect some of the sun's light and heat back into space. And a new study says it might just be our cheapest option.

Environmental Research Letters recently published a cost analysis that found it would only cost $5 billion a year to deliver material into the stratosphere that could block and reduce the amount of sunlight hitting the earth. That is, the authors point out, less than the usual estimated cost of reducing carbon emissions: 0.2-2.5% of global GDP (about $200 billion-$2 trillion), and much less than the 5-20% of global GDP that British economist Nicholas Stern estimated that climate change will cost us each year if we do nothing.

There are at least six ways scientists think we could get enough sun-blocking material (about 1-5 million metric tons) into the appropriate place in the atmosphere (11-18 miles above the earth): existing aircrafts; new airplanes designed to fly at the required higher altitude; a hybrid airship that generates lift via buoyancy forces like helium; a rocket powered glider; guns; and a space elevator consisting of a large pipe, rising 12 miles into the air, suspended by a helium-filled floating platform.

Unbelievably, it appears it’s cheaper to construct a space elevator than it is to change our collective daily habits so that they emit fewer emissions. And, paradoxically perhaps, it's cheaper to build a helium propelled hybrid airship than it is to do nothing.

Opponents of geoengineering argue that even doing preliminary research detracts from the more important task of lowering carbon emissions. And even supporters are wary of putting the theories into practice. “It is hyperbolic to say this, but no less true,” David Kieth, an engineering and public policy professor at Harvard told The New Yorker staff writer Michael Specter in an article in May. “When you start to reflect light away from the planet, you can easily imagine a chain of events that would extinguish life on earth.”

So why would we ever take that chance? Specter writes that “There is only one reason to consider deploying a scheme with even a tiny chance of causing such a catastrophe: if the risks of not deploying it were clearly higher.”

In light of our summer of extremes, the risks of doing nothing may be mounting. But in the same way some of us eschew health insurance, it is the cheapest—not the best—option that often wins out. Consequences be damned.