Global Sunblock Using Sulfur

Last week's podcast of CBC's Quirks and Quarks discusses the radical idea of blocking the sun's rays to mitigate climate change. Bob McDonald interviews Dr. David Keith, the Canada Research Chair in Energy and the Environment at the University of Calgary. Keith is not necessarily recommending the idea but he does believe we should put it on the research agenda. One option -- a pretty shocking one -- is to release sulfur into the upper atmosphere. From volcanic activity in the past, we already know this would have an immediate cooling effect on the climate.

Nobel Prize winning atmospheric chemist Paul Crutzen^ also recommends looking into such research [PDF]. But he warns:

I must stress here that the albedo enhancement scheme should only be deployed when there are proven net advantages and in particular when rapid climate warming is developing, paradoxically, in part due to improvements in worldwide air quality. Importantly, its possibility should not be used to justify inadequate climate policies, but merely to create a possibility to combat potentially drastic climate heating.

Keith says in the podcast that many climate scientists are reluctant to discuss this because it would only treat the symptoms of climate change and not the cause. At the same time, he found policy-makers who were all too eager to deploy such a program.

In this panel discussion on geoengineering, Harvard geochemist Dan Schrag^ points out:

If we're going to use the Earth as an experiment -- which we're already doing by adding greenhouse gases -- if we're going to do an experiment by testing injection of reflective material, say, sulfur, into the stratosphere, we don't have a control. And so if something happens, it's almost impossible, given the complexity of the system, to attribute it either to the CO2 or the sulfur.

Sulfur injection into the upper atmosphere, says Keith, is within the power of poorer nations and even within the power of the richest individuals. And like the current trend in climate change, there would be winners and losers. Since we are already altering the atmosphere, is this something we should consider? And if so, who would be responsible? Who should be allowed to fiddle with the global thermostat?