Practical Concerns Add Potential Risk Factors for Stratospheric Aerosol Injection Strategies

MIRANDA HACK, V. Faye McNeill, Dan Steingart, Gernot Wagner, Columbia University

     Abstract Number: 237
     Working Group: Aerosol Physics

Abstract
High-altitude aerosols have the potential to lower global temperatures by backscattering a small fraction of incident shortwave radiation, a phenomenon best understood through the formation of stratospheric sulfate aerosol in the wake of volcanic eruptions. With the ability to rapidly and inexpensively offset warming, climate mitigation via stratospheric aerosol injections (SAI) presents an opportunity to temper key climate risks as a potential supplement to addressing the root cause by cutting greenhouse-gas emissions. But such a strategy is not without considerable environmental risk itself. Solid mineral candidates have been proposed as an alternative to sulfate SAI, potentially minimizing the associated risks of ozone depletion and localized stratospheric warming. However, practical and interdisciplinary limitations of SAI – particularly as it pertains to the deployment of the proposed “lower-risk” mineral candidates” – have largely gone unexplored.

Macroscopic factors like governance and degree of deployment coordination may influence resultant aerosol lifetimes and sAODs, which often dictate tropospheric climate impacts, while supply chain factors add limitations to feasible candidate selection. Microscopic factors, predominantly dispersal and injection technology, will play a key role in governing the resultant size distributions and radiative properties of proposed solid mineral aerosol candidates. Here, we show that these practical considerations fundamentally dictate the magnitude of and distribution of risk associated with an SAI strategy. Technical, geopolitical, and economic constraints will ultimately narrow the design – and associated risk – space for feasible SAI strategies.