ZPEnergy.com - Guns and sunshades to rescue climate

Seanpu1 writes: Thought this might interest the group. Scientists are contemplating engineering Earths atmosphere to compensate for "global warming" rather than changing the way we use energy.

Guns and sunshades to rescue climate /By Molly Bentley (BBC News)

Any cook who has tasted a dish after tossing in too much salt or hot pepper knows the panic of trying to undo the damage.

You raid the spice rack to mask the glut of cayenne, but oops - now it is swimming in oregano. It is hard to restore the balance once you overdo it.

We have experienced this with the Earth's atmosphere for some time now; concentrations of greenhouse gases continue to grow even as we adopt international protocols and clean technologies in an attempt to bring them down.

It is apparent our energy-saving tricks are not enough to prevent perhaps catastrophic climate change. But there may be a "plan B"; and while scientists hope it will not be needed, they are considering it anyway.

It would be plucked from an array of bold and contentious proposals which go under the heading "geoengineering".

Feasible or far-out?

"Humans are changing the Earth, and it's a big effect we're having," says Mike MacCracken, chief scientist for climate change projects at the Climate Institute in Washington DC.

"To really stop climate change in its tracks, you have to go to virtually zero emissions in the next two decades.

"So the question is, is there a silver bullet that can help us to limit the amount of climate change?"

Some such "silver bullets" aim to scrub carbon dioxide (CO2) out of the atmosphere, some to cool Earth directly by veiling it; others are yet more radical.

While most are confined to computer models or scribbling on the backs of envelopes, a few have been tried cautiously.

Scientists have sprinkled iron in patches of the Southern Ocean to increase absorption of carbon dioxide from the atmosphere, and are testing the feasibility of sequestering carbon in saltwater aquifers or rock.

But what distinguishes geoengineering from localised tinkering is the scope; this would be manipulation on a global scale.

Earth in the shade

Consider the notion of shading the planet with mirrors. The US National Academy of Sciences found that 55,000 orbiting mirrors would reflect enough sunlight to counter about half the doubling of carbon dioxide.

But each mirror must be 100 sq km; any larger and you would need a manufacturing plant on the Moon, says Dr MacCracken. The price tag of space-based fixes makes them prohibitive - for now.

By contrast, the "human-volcano" approach is on terra firma and less costly. Inspired by studies of the Mt Pinatubo eruption of 1991 and the cooling effect of its sulphur plume, one proposal suggests that naval guns shoot sulphur pellets into the air to increase Earth's albedo, or reflectivity...

Read the whole article here: http://news.bbc.co.uk/1/hi/sci/tech/4762720.stm