Just how close are we exactly to launching a large-scale solar geoengineering project? That’s the question a new study published recently in Environmental Research Letters tried to answer. The study looked at the realities behind the idea of injecting aerosols into the atmosphere from high-altitude aircraft in an attempt to reduce Earth’s warming.
Though the idea isn’t new, the technology behind it is still unreasonably expensive, determined the study. While there are several contemplated methods of injecting sulphates into the lower stratosphere (a process called stratospheric aerosol injection or SAI), the costs of implementing any of the currently available methods are not practical on a large scale.
The researchers considered the case of one such hypothetical project that would commence in fifteen years with the intention of using SAI to cut the increase in anthropogenic radiative forcing in half. Co-author Dr. Gernot Wagner commented: "While we don't make any judgment about the desirability of SAI, we do show that a hypothetical deployment program starting 15 years from now, while both highly uncertain and ambitious, would be technically possible strictly from an engineering perspective. It would also be remarkably inexpensive, at an average of around $2 to 2.5 billion per year over the first 15 years."
Wagner’s co-author, Wake Smith, explained that part of the expense comes from the infeasibility of current aircraft to do the job. “It would indeed take an entirely new plane design to do SAI under reasonable albeit entirely hypothetical parameters,” he said. “No existing aircraft has the combination of altitude and payload capabilities required." Such an aircraft would have to be able to sustain level flight at 20 kilometers.
Smith and Wagner elaborated more on the design of this futuristic stratosphere-flying plane, which they call SAIL, or SAI Lofter. Using measurements and data from aerospace and engine companies, the researchers developed the hypothetical SAIL: “It's equivalent in weight to a large, narrow body passenger aircraft. But to sustain level flight at 20 kilometers, it needs roughly double the wing area of an equivalently sized airliner, and double the thrust, with four engines instead of two. At the same time, its fuselage would be stubby and narrow, sized to accommodate a heavy but dense mass of molten sulphur rather than the large volume of space and air required for passengers."
Nevertheless, don’t get too excited about this solar geoengineering future – the authors don’t think the idea is that close to becoming a reality just yet.