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By Kelly

Today we are back on the subject of geo-engineering. An article in Nature Climate Change reminded me that I had promised to write on the feasibility of injecting foreign particles into our atmosphere, in an attempt to avoid the direst consequences of climate change. I started with geo-engineering the oceans by fertilizing them with iron, a technique that falls under Carbon Dioxide Removal (CDR). Today is the first of the Solar Radiation Management (SRM) techniques that attempt to diminish the greenhouse effect by deflecting incoming solar radiation back into space (see above).

Last weeks paper was not a report on the science of aerosol injection per se, rather on the public engagement that assessed the layman’s perception, and acceptance, of a field trial for Stratospheric Particle Injection for Climate Engineering (SPICE). Perhaps not surprisingly, the participants were hesitant to support full-scale aerosol injection, however agreed that a field trial was worth pursuing. But before getting to the interesting ethical and social issues raised during the study….a word on the science.

The sun’s energy entering our atmosphere warms the Earth’s surface and makes our planet habitable. The energy that is not absorbed, is reflected back into space as long-wave radiation. Greenhouse gases, including CO2, partially trap this outgoing radiation, and scatter it in all directions causing the lower atmosphere and land to warm further. By burning fossil fuels without constraint we have created the enhanced greenhouse, trapping too much of this warmth. And here is where aerosols can help. By injecting particles into the stratosphere we can shade the planet by not allowing so much of the sun’s energy to enter our atmosphere in the first place; also termed global dimming. You can think of it as putting millions of little band-aids up in the stratosphere….And we know that this works as this process occurs naturally (aerosols, not band aids). In 1991, Mount Pinatubo erupted spewing thirty million tonnes of aerosols  into the stratosphere cooling global temperatures by ~0.5 degree. There was also a temporary depletion of the ozone layer but let’s not ruin a good story by focusing on the negative.

I thought the SPICE study was fascinating as it attempted to address the logistics of being a volcano. However, rather than tapping into a magma chamber, they went for the more logistically simplistic ‘balloon and pipe’ set up, first proposing to get water up a 1 km scaled-down version of the full-scale 25km delivery system (see inset below).

But what of public opinion? Concerns included the relevance of the scaled-down version at mimicking the full-scale project, and whether it accurately represented the risk, both locally and in a broader environmental sense. Other prominent issues surrounded governance of the full-scale project. Who decides when and where aerosols would be released, and how do we reach consensus? None of the participants were keen to have the test project conducted in the vicinity of their homes. So whose backyard will it be?

The appalling lack of consensus at international meetings does not instill hope, with the failings of Kyoto given as an example. And even if we could reach consensus, who pays for it? Who owns the shade? And how can we guarantee its maintenance? Particularly, as one participant sagely added, if we don’t reign in emissions there will be an even hotter planet when the shade comes down.

Geo-engineering troubles me greatly. I see these solutions as a means of avoiding the lifestyle changes required for so many people to comfortably occupy this planet. After all, you can only sweep things under the rug for so long before you create a 25km trip hazard.

For the full article in Nature Climate Change click here (you’ll need a subscription though), or for further reading click here.