This document is a white paper prepared at the request of the Scientific Assessment Panel (SAP) of the Montreal Protocol. We briefly review the literature regarding the volcanogenic production of chlorofluorocarbons within the context of the East Asian CFC-11 emissions anomaly first described in 2018. We conclude that volcanic emissions of CFC-11 cannot account for the observed emissions anomaly.
David Wilmouth's Publications
Klobas, J. Eric and David M. Wilmouth. 2019. Volcanogenic chlorofluorocarbons and the recent CFC anomalies. Harvard University, Cambridge, MA. https://dash.harvard.edu/handle/1/39913598.
Wilmouth, D. M., and D. S. Sayres (2019), Rayleigh scattering cross sections of argon, carbon dioxide, sulfur hexafluoride, and methane in the UV-A region using Broadband Cavity Enhanced Spectroscopy, Journal of Quantitative Spectroscopy and Radiative Transfer 234, 32-39, doi:10.1016/j.jqsrt.2019.05.031.
Accurate Rayleigh scattering cross sections are important for understanding the propagation of electromagnetic radiation in planetary atmospheres and for calibrating mirror reflectivity in high finesse optical cavities. In this study, we used Broadband Cavity Enhanced Spectroscopy (BBCES) to measure Rayleigh scattering cross sections for argon, carbon dioxide, sulfur hexafluoride, and methane...
Burkholder, J. B., S. P. Sander, J. Abbatt, J. R. Barker, C. Cappa, J. D. Crounse, T. S. Dibble, R. E. Huie, C. E. Kolb, M. J. Kurylo, V. L. Orkin, C. J. Percival, D. M. Wilmouth, and P. H. Wine "Chemical Kinetics and Photochemical Data for Use in Atmospheric Studies, Evaluation No. 19," JPL Publication 19-5, Jet Propulsion Laboratory, Pasadena, 2019, http://jpldataeval.jpl.nasa.gov.
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Wilmouth, D. M., R. J. Salawitch, and T. P. Canty, "Stratospheric Ozone Depletion and Recovery," a chapter in Green Chemistry: An Inclusive Approach, Torok, B., and T. Dransfield (Eds.) Elsevier Publishing, 2018, p.177–209.
This chapter provides an overview of the depletion of Earth’s ozone layer due to human activity and the eventual recovery due to legislation that banned ozone-depleting substances (ODSs) such as chlorofluorocarbons (CFCs) and bromine-bearing halon gases. The importance of ozone in protecting life on Earth is introduced, followed by details on how the release of CFCs and halons led to significant...
Anderson, J. G., D. K. Weisenstein, K. P. Bowman, C. R. Homeyer, J. B. Smith, D. M. Wilmouth, D. S. Sayres, J. E. Klobas, S. S. Leroy, J. A. Dykema, and S. C. Wofsy (2017), Stratospheric ozone over the United States in summer linked to observations of convection and temperature via chlorine and bromine catalysis, Proceedings of the National Academy of Sciences 114: E4905-E4913; doi: 10.1073/pnas.1619318114.
We present observations defining (i) the frequency and depth of convective penetration of water into the stratosphere over the United States in summer using the Next-Generation Radar system; (ii) the altitude-dependent distribution of inorganic chlorine established in the same coordinate system as the radar observations; (iii) the high resolution temperature structure in the stratosphere over the...
Smith, J. B., D. M. Wilmouth, K. M. Bedka, K. P. Bowman, C. R. Homeyer, J. A. Dykema, M. R. Sargent, C. Clapp, S. S. Leroy, D. S. Sayres, J. M. Dean-Day, T. P. Bui, and J. G. Anderson (2017), A case-study of convectively sourced water vapor observed in the overworld stratosphere over the United States, J. Geophys. Res. Atmos. 122, doi:10.1002/2017JD026831.
On 27 August 2013, during the Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys field mission, NASA's ER‐2 research aircraft encountered a region of enhanced water vapor, extending over a depth of approximately 2 km and a minimum areal extent of 20,000 km2 in the stratosphere (375 K to 415 K potential temperature), south of...
Klobas, J. E., D. M. Wilmouth, D. K. Weisenstein, J. G. Anderson, and R. J. Salawitch (2017), Ozone depletion following future volcanic eruptions, Geophys. Res. Lett. 44, 7490-7499; doi: 10.1002/2017GL073972.
While explosive volcanic eruptions cause ozone loss in the current atmosphere due to an enhancement in the availability of reactive chlorine following the stratospheric injection of sulfur, future eruptions are expected to enhance total column ozone as halogen loading approaches pre-industrial levels. The timing of this shift in the impact of major volcanic eruptions on the thickness of the ozone...
, , and (2016), The kinetics of the ClOOCl catalytic cycle, J. Geophys. Res. Atmos., 121, 13,768–13,783, doi:10.1002/2016JD025710.
We use simultaneous in situ observations of [ClO] and [ClOOCl] obtained in the Arctic polar vortex to evaluate the kinetics of the ClOOCl catalytic cycle. Available laboratory measurements of the ClOOCl absorption cross sections, the ClO + ClO + M reaction rate constant, and the ClO/ClOOCl equilibrium constant are considered, along with compendium evaluations of these...
J. B. Burkholder, S. P. Sander, J. Abbatt, J. R. Barker, R. E. Huie, C. E. Kolb, M. J. Kurylo, V. L. Orkin, D. M. Wilmouth, and P. H. Wine "Chemical Kinetics and Photochemical Data for Use in Atmospheric Studies, Evaluation No. 18," JPL Publication 15-10, Jet Propulsion Laboratory, Pasadena, 2015, http://jpldataeval.jpl.nasa.gov.
Anderson, J. G., D. M. Wilmouth, J. B. Smith, and D. S. Sayres, UV Dosage Levels in Summer: Increased Risk of Ozone Loss from Convectively Injected Water Vapor, Science 337, 835 (2012).
The observed presence of water vapor convectively injected deep into the stratosphere over the United States can fundamentally change the catalytic chlorine/bromine free-radical chemistry of the lower stratosphere by shifting total available inorganic chlorine into the catalytically active free-radical form, ClO. This chemical shift markedly affects total ozone loss rates and makes the catalytic...