Solar shields to cut global warming?
Published: 1 June 2009
Author: Meera Dattani
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[ 5 ] Comments
Solar shields are back on the agenda to save the planet
As scientists pore over the options to fight climate change, an old one re-emerges. Once consigned to the box of crazy concepts, deflecting the sun's rays via a solar shield is back on the table.
It started with a bang
In 1991, Mount Pinatubo in the Philippines exploded and the 20million tons of sulphur dioxide (SO²) which rose into the stratosphere reflected the sun's heat back into space. The consequence? Global temperatures dropped by half a degree Celsius, compared to 100 years prior, when greenhouse gases had increased temperatures by 1%.
Temperatures did eventually rise, but it opened up possibilities that air could be cooled artificially.
How would it work?
SO² could be launched from rockets, sprayed from high-altitude planes or released from an enormous chimney into the upper atmosphere where it would combine with other molecules, creating a reflective barrier. Nobel-Prize winning scientist Paul Crutzen estimates the SO² released would be relatively small, about 1.5million tons (some say 5million tons). The notion is, unsurprisingly, controversial.
Will it happen anytime soon?
Geo-engineering (manipulating the earth's climate to fight global warming) was first touted in the 1960s, but it remains relatively new territory. Nobel Laureates Paul Crutzen and Thomas Schelling advocate the need for a climate plan and the British Royal Society will report on their study in September.
The US National Academies of Science is also active. One collaborator, Princeton climate scientist Michael Oppenheimer, told Newsweek he supports academic research, while Harvard climatologist Dan Schrag proposes speedier action.
Professor John Shepherd of the British Royal Society told Sideways News, ‘Solar shields are an idea. More serious model runs will be needed first.' But the fact they're being discussed is a milestone. He admits some people were nervous about discussing this idea, for reasons of credibility, but Crutzen's backing has helped.
What else is on the table?
Other options include ocean fertilisation, CCS and biochar. Edward Teller, dubbed "father of the hydrogen bomb", suggested floating reflective metal particles in the atmosphere. Other (costlier) options include propelling mirrors and shields into space.
SO² could be launched from rockets, sprayed from high-altitude planes or released from an enormous chimney into the upper atmosphere where it would combine with other molecules, creating a reflective barrier
The drawbacks
SO² could damage the ozone layer, exposing the Southern Hemisphere to ultraviolet radiation. One solution is releasing gases slowly; if problematic, it could be halted and residual SO² would disperse. Ken Caldeira of California's Carnegie Institution of Washington told New Scientist, ‘Personally, as a citizen not a scientist, I don't like geo-engineering because of the high environmental risk. It's toying with poorly understood complex systems.'
And could carbon emission-cutting drop off the political agenda if it was ‘easy' to lower temperatures artificially? Professor Shepherd said, ‘Solar radiation works relatively fast. However, if you stop it, global warming could accelerate. Conversely, removing CO² is a slower process but only acts at source. You're caught between the devil and the deep blue sea.'
Why now and not earlier?
Kyoto set carbon-cutting targets for 2012, but 21 out of 40 countries have seen levels rise. The top two carbon emitters China and the USA did not sign. The consequences are potentially disastrous; increased droughts, flooding, rising sea levels. That's why solar shields, once dismissed as dangerous and ridiculous, are being discussed again.
SIDEWAYS News for fresh perspectives
Comments
Geo-engineering of the Earth’s climate is already taking place. Governments around the world are using planes to spray aerosol chemicals at high altitude. Look up into the sky on days when there are few clouds and you can see the planes overhead with long trails of white coming from them. These long white trails are chemicals. These white trails hang in the sky from a few minutes to many hours slowly spreading out forming a white haze.
Re Solar shields:
How about creating a Sand-Slick barrier in a high level orbit above the earth.( I think the term for an orbit relative to the suns appearance around the Earh is a Solar Sychronus Orbit). We could spread sand in a manner similar to using road gritting... but using a fleet of shuttles. As long as we only spread a thin layer, (admittedly a blanket a few miles square), the suns rays will still penetrate our atmosphere but some will be reflected away harmlessly. The effects can be monitored and the spread alterd accordingly.
In essense we put a layer of sand between the Earth and the sun in an orbit that keeps the Sun , sand and Earth in a constant line.
For best effect, the sand would be positioned on an orbit around the equator, thus reducing the massive temperatures in countries of similar lattitude. Obviouly transportation would be expensive, but sand is free and the technology exits, we could start tommorrow.
I apprecite that this idea doent tackle the manmade causes of global warming, but it may give us more time. Comments welcomed
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How much will all this cost and how will countries coordinate how it all works so that it shelters the whole planet. Where there's a will there's a way I guess!
A brilliant idea but it doesn't really solve the problem of the causes of climate change
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