title: Stratospheric controlled perturbation experiment: a small-scale experiment to improve understanding of the risks of solar geoengineering.
abstract: Although solar radiation management (SRM) through stratospheric aerosol methods has the potential to mitigate impacts of climate change, our current knowledge of stratospheric processes suggests that these methods may entail significant risks. In addition to the risks associated with current knowledge, the possibility of 'unknown unknowns' exists that could significantly alter the risk assessment relative to our current understanding. While laboratory experimentation can improve the current state of knowledge and atmospheric models can assess large-scale climate response, they cannot capture possible unknown chemistry or represent the full range of interactive atmospheric chemical physics. Small-scale, in situ experimentation under well-regulated circumstances can begin to remove some of these uncertainties. This experiment-provisionally titled the stratospheric controlled perturbation experiment-is under development and will only proceed with transparent and predominantly governmental funding and independent risk assessment. We describe the scientific and technical foundation for performing, under external oversight, small-scale experiments to quantify the risks posed by SRM to activation of halogen species and subsequent erosion of stratospheric ozone. The paper's scope includes selection of the measurement platform, relevant aspects of stratospheric meteorology, operational considerations and instrument design and engineering.
authors.affiliation: School of Engineering and Applied Sciences, Harvard University, One Brattle Square, Cambridge, MA 02138, USA dykema@huarp.harvard.edu.
authors.forename: John A
authors.identifier: http://orcid.org/0000-0001-7611-6163
authors.initials: JA
authors.lastname: Dykema
authors.affiliation: School of Engineering and Applied Sciences, Harvard University, One Brattle Square, Cambridge, MA 02138, USA Harvard Kennedy School and School of Engineering and Applied Science, Pierce Hall, 29 Oxford Street, Cambridge, MA 02138, USA.
authors.forename: David W
authors.initials: DW
authors.lastname: Keith
authors.affiliation: School of Engineering and Applied Sciences, Harvard University, One Brattle Square, Cambridge, MA 02138, USA Department of Chemistry and Chemical Biology, Harvard University, Mallinckrodt Link Building, 12 Oxford Street, Cambridge, MA 02138, USA.
authors.forename: James G
authors.initials: JG
authors.lastname: Anderson
authors.affiliation: School of Engineering and Applied Sciences, Harvard University, One Brattle Square, Cambridge, MA 02138, USA.
authors.forename: Debra
authors.initials: D
authors.lastname: Weisenstein
keywords: balloon; geoengineering; ozone depletion; solar radiation management; stratosphere