External oversight and adherence to established safety practices are an essential part of the SCoPEx approach to risk
management. The physical risks associated with scientific ballooning and custom instrumentation are managed using standard methods applied across all balloon
missions. The size of the chemical perturbations in SCoPEx is tiny relative to chemical perturbations caused by a few minutes of flight of a commercial
In summary, we have presented a case for an outdoor experiment to test the risks and efficacy of SRM. The motivation for outdoor
experimentation is grounded in a larger scientific context and in the need to reduce uncertainties inherent in representing the complex atmospheric system in
the laboratory, by a natural analogue, or in a model. The scientific results are expected to inform theoretical predictions about stratospheric composition in
a changing climate with high-resolution, high-accuracy data.
We thank the fund for Innovative Climate and Energy Research, Southwest Research Institute, Aurora Flight Sciences, NASA for
MERRA data, and four anonymous reviewers for their insightful comments.
1 - Govindasamy B, Thompson S, Duffy PB, Caldeira K,
Delire C. 2002
Impact of geoengineering schemes on the terrestrial biosphere.
2 - Govindasamy B, Caldeira K, Duffy PB. 2003
Geoengineering Earth's radiation balance to mitigate climate change from a quadrupling of CO2. Glob. Planet.
3 - Caldeira K, Wood L. 2008
Global and Arctic climate engineering: numerical model studies.
4 - Rasch PJ, et al. 2008
An overview of geoengineering of climate using stratospheric sulphate aerosols.
5 - Robock A, Oman L, Stenchikov GL. 2008
Regional climate responses to geoengineering with tropical and Arctic SO2 injections.
6 - Tilmes S, Garcia RR, Kinnison DE, Gettelman A, Rasch PJ. 2009
Impact of geoengineered aerosols on the troposphere and stratosphere.
7 - Heckendorn P, et al. 2009
The impact of geoengineering aerosols on stratospheric temperature and ozone.
8 - Pierce JR, Weisenstein DK, Heckendorn P, Peter T, Keith DW. 2010
Efficient formation of stratospheric aerosol for climate engineering by emission of condensible vapor from aircraft.
9 - Niemeier U, Schmidt H, Timmreck C. 2011
The dependency of geoengineered sulfate aerosol on the emission strategy.
10 - English JM, Toon OB, Mills MJ. 2012
Microphysical simulations of sulfur burdens from stratospheric sulfur geoengineering.
11 - Tilmes S, et al. 2012
Impact of very short-lived halogens on stratospheric ozone abundance and UV radiation in a geo-engineered
12 - Tilmes S, Müller R, Salawitch R. 2008
The sensitivity of polar ozone depletion to proposed geoengineering schemes.
13 - Hanson DR, Ravishankara AR. 1994
Reactive uptake of ClONO2 onto sulfuric acid due to reaction with HCl and H2O.
Wennberg PO, et al. 1994
Removal of stratospheric O3 by radicals: in situ measurements of OH, HO2, NO, NO2, ClO, and BrO.
15 - Peter T, Grooß J. 2012
Polar stratospheric clouds and sulfate aerosol particles: microphysics, denitrification and heterogeneous chemistry.
16 - Newman PA, et al. 2002
An overview of the SOLVE/THESEO 2000 campaign.
17 - Hanisco TF, et al. 2002
Quantifying the rate of heterogeneous processing in the Arctic polar vortex with in situ observations of OH.
18 - Hanisco TF, Smith JB, Stimpfle RM, Wilmouth DM, Anderson JG,
Richard EC, Bui TP. 2002
In situ observations of HO2 and OH obtained on the NASA ER-2 in the high-ClO conditions of the 1999/2000 Arctic polar
19 - Carslaw KS, et al. 2002
A vortex-scale simulation of the growth and sedimentation of large nitric acid hydrate particles.
20 - Stimpfle RM, Wilmouth DM, Salawitch RJ, Anderson JG. 2004
First measurements of ClOOCl in the stratosphere: the coupling of ClOOCl and ClO in the Arctic polar vortex.
21 - Shi Q, Jayne JT, Kolb CE, Worsnop DR, Davidovits P. 2001
Kinetic model for reaction of ClONO2 with H2O and HCl and HOCl with HCl in sulfuric acid solutions.
22 - Toon OB, Hamill P, Turco RP, Pinto J. 1986
Condensation of HNO3 and HCl in the winter polar stratospheres.
23 - Crutzen PJ, Arnold F. 1986
Nitric acid cloud formation in the cold Antarctic stratosphere: a major cause for the springtime ozone hole.
24 - Solomon S. 1999
Stratospheric ozone depletion: a review of concepts and history.
25 - McElroy MB, Salawitch RJ, Wofsy SC, Logan JA. 1986
Reductions of Antarctic ozone due to synergistic interactions of chlorine and bromine.
26 - Salawitch RJ, et al. 2005
Sensitivity of ozone to bromine in the lower stratosphere.
27 - Kawa SR, et al. 2009
Sensitivity of polar stratospheric ozone loss to uncertainties in chemical reaction kinetics.
28 - Held IM, Soden BJ. 2000
Water vapor feedback and global warming
29 - Zhang Z, Yang P. 2008
Water-vapor climate feedback inferred from climate fluctuations, 2003–2008.
30 - Fasullo J, Sun DZ. 2001
Radiative sensitivity to water vapor under all-sky conditions.
31 - Kirk-Davidoff DB, Schrag DP, Anderson JG. 2002
On the feedback of stratospheric clouds on polar climate.
32 - Francis JA, Vavrus SJ. 2012
Evidence linking Arctic amplification to extreme weather in mid-latitudes.
33 - Holton JR, Haynes PH, McIntyre ME, Douglass AR, Rood RB,
Pfister L. 1995
34 - Ploeger F, et al. 2013
Horizontal water vapor transport in the lower stratosphere from subtropics to high latitudes during boreal summer.
35 - JG, Wilmouth DM, Smith JB, Sayres DS. 2012
UV dosage levels in summer: increased risk of ozone loss from convectively injected water vapor.
36 - Rosenlof KH, et al. 2001
Stratospheric water vapor increases over the past half-century.
37 - Kunz, A., et al. 2013
Extending water vapor trend observations over Boulder into the tropopause region: trend uncertainties and resulting radiative
38 - Urban J, Losso
w S, Stiller G, Read W. 2014
Another drop in water vapor.
Temperature trends in the tropical upper troposphere and lower stratosphere: connections with sea surface temperatures and implications for water vapor and