The professor of public policy and applied physics at University of Harvard proposes to shade the Earth by imitating the process during large volcanic eruptions. Injecting sulfate particles into the atmosphere should theoretically cool the planet. Fossil fuels power plants emit around 50 million tons of these sulfate particles per year. However, these are sent to the lower atmosphere, where these particles stay airborne for limited periods of time. If sent in the stratosphere, however, they trigger the cooling effect. According to Keith, one million tons per year are needed to have the needed cooling effect.
Although geo-engineering is thought to alter patterns of precipitation, Keith suggests that injecting sulfate particles would not cause this. He argues the opinion of some critics that geo-engineering might change the monsoon patterns and affect agricultural practices in South and Souteast Asia. Exactly the opposite, Keith states that injecting sulfate particles might boost crop productivity by decreasing average temperatures.
He proposes that the introduction of sulfate particles happens gradually. This will not completely eliminate warming, but rather it will decrease the rate of warming to half its current number. He hired a team of specialists who estimated that a billion dollars a year and 100 aircrafts would be sufficient to execute the procedure.
Of course, a concern that cannot be easily ignored is the effect these particles have on the atmosphere. It is already established that they can deplete the ozone layer. To tackle this, Keith proposes to conduct a test where water vapor and sulfate clouds are introduced in the stratosphere, and to measure the effect quantitatively.
Even if geo-engineering techniques work out, and the warming effect is reduced, Keith is still certain that efforts should be put to reduce the emissions. Problems such as ocean acidification will not be solved by injecting sulfate. He notes that there is not enough knowledge to start the process just yet, however he is certain that this will reduce the risks.
Via: Technology Review