In order to completely compensate the climate warming as a result of elevated greenhouse gas concentrations each year 1 to 5 megatonnes of albedo-enhancing aerosols would have to be delivered to a stratospheric zone between 18 and 30 kilometers altitude.

According to Justin McClellan of Aurora Flight Science Corporation, David Keith of Harvard University and Jay Apt of Carnegie Mellon University the cost of such an operation would vary between 1 and 8 billion dollars annually depending on delivery method – and of course warming scenarios.

It is not the first time these scientists have tried to come up with a cost comparison for such stratospheric SRM geoengineering. In 2010 the researchers concluded the best option would be to design special aircraft to deliver the aerosols – and in their new 2012 publication in Environmental Research Letters they reach a similar conclusion.

Lifting enormous slurry pipes [with balloons?] 20 km up high may be competitive financially, ‘but the research, development, testing and evaluation costs of these systems are high and carry a large uncertainty; the pipe system’s high operating pressures and tensile strength requirements bring the feasibility of this system into question.’ Rockets and guns as carriers are the most expensive option.

So aircraft would have to save the climate after all. How about that for a nice PR move.

© Rolf Schuttenhelm | www.bitsofscience.org