Re-examining the cost of stratospheric aerosol injection

Abstract:

Conventional wisdom holds that the direct cost of stratospheric aerosol injection (SAI) is low, indicating that its technical barrier is small. This is one of the reasons why SAI is receiving so much attention from natural and social scientists alike. Such estimates are, however, few and subject to appraisal optimism or optimism bias.

Here we review the literature on the SAI and synthesise published estimates of the related parameters in order re-examine the SAI direct cost and operational scale, another measure of the technical barriers. Although references are often made to a "few billion dollars" as the SAI cost, our re-analysis shows that the cost of a 2 W/m²cooling could reach 100 billion dollars per year in the case of aircraft-based SAI with sulfates, with a required fleet size of about 1000 airplanes. There are approaches to trim the cost and scale, such as using soot instead of sulfates and developing dedicated, new aircraft. The choice of black carbon, however, would present significant environmental risks.

Since the cheapness of SAI underlies the governance debate, our results point to the need of a more systematic analysis of the engineering aspects of SAI.