As it has become increasingly clear that we are well into a period of dangerous or even catastrophic climate change, discussions about geoengineering have become more intense and public.  Now the US government is openly admitting that it too is discussing the pros and cons of geo-engineering.  This article includes some fascinating insights into these discussions.   Newly appointed White House science advisor, John Holdren, told the Associated Press, for example, that “as the global climate picture gets gloomier, geoengineering is sneaking into White House conversations”.

“It’s got to be looked at,” Holdren said. “We don’t have the luxury of taking any approach off the table.”

Percentage of diffusely reflected sun light in relation to various surface conditions of the Earth (source: Wikipedia)

Sounds to me like geoengineering is very much on the agenda! There are various aspects which contribute to the diffuse reflectivity of the planet – such as clouds, ice and snow and even vegetation.  The graph on the left shows the various contributions of different aspects of the planet to its albedo.  These various characteristics have a powerful role in determining the earth temperature.  The recent loss of summer Arctic ice is a case in point.  Calculations show that the resulting “albedo flip” from reflective ice to darker ice-free ocean will dramatically increase the energy being absorbed by the earth and drive its temperature upward by over a degree Celsius.

Various ideas have been floated about on how to increase the reflectivity of the earth – including pumping reflective particles into the outer atmosphere of the earth in order to bounce more energy back into space.  These calculations suggest that relatively small amounts of material could lower the earth’s temperature by as much as 1-2°C.  The contribution to lowering temperature such as this would certainly take some of the pressure off and buy us important time as we urgently struggle to get greenhouse emissions under control.

But there is reason for great caution. Apart from the fact that there are many uncertainties and unknowns (i.e. are we certain that we know how much of these yet-to-be-invented particles to add to the atmosphere?), there is the concern that offering this option will take the pressure off governments to act decisively on the problem of fossil fuels and their emissions.  It also has a range of legal and ethical issues.  For example, should any particular government be able to unilaterally decide whether or not to manipulate the earth’s albedo and temperature without the agreement from all?  And if manipulating temperature downward were to result in deaths from cooling temperatures or disturbances in the weather, what then?

And it is important to remember that changing the albedo of the earth will not solve all the problems associated with upwardly spiralling atmospheric carbon dioxide.  For example, decreasing the temperature of the planet will do nothing to solve the problem of ocean acidification.