The U.S. House Committee on Science and Technology has held a series of hearings over the past year on climate geoengineering.  The recent testimony of Dr. Philip Rasch of the Pacific Northwest National Laboratory would be a very good class reading for a geoengineering module because it explores a number of important issues, including the potential cost of such schemes, the contours of research and deployment, potential time lags in impacts, and a good explanation of the mechanisms of the two primary solar radiation management, stratospheric sulfate aerosol and tropospheric cloud seeding.

Among the key take-aways in the testimony:

1. Relevant activities for geoengineering research include assessment and evaluation of potential strategies, computer modeling, , labor and field works, technology development and deployment;
2. Even prior to deployment, any nation engaging in a geoengineering program would require “enormous activity,” comparable in scope to the Intergovernmental Panel on Climate Change’s modeling and assessing activities, the Manhattan Project, or both;
3. A rough estimate of the cost of full deployment of a stratospheric sulfur dioxide aerosol scheme would be a few billion dollars; expenditure of $10-50 million annually would have “an enormous effect” on research activities;
4. While we would have “strong hints” as to whether stratospheric sulfate aerosols were effective within a couple of years of deployment, scientists would be more comfortable with such an assessment in 5-10 years; it also would take multiple years to sort out both the positive and potential negative implications of deployment (negative implications could include regional declines in precipitation, depletion of the ozone layer);
5. There would be substantial difficulties in evaluating sulfur dioxide aerosol injection  schemes without full deployment; for example introducing aerosol over a small patch of Earth would result in rapid dilution, and thus we wouldn’t expect the aerosols to dilute in the same way as with more extensive deployment;
6. If society were to deploy a cloud seeding scheme to enhance cloud albedo, noticeable temperature impacts would occur within a couple of years, but it would also take a number of years to assess potential negative consequences, e.g. changes in major precipitation systems.

Related posts:

1. New Article on Solar Radiation Management Geoengineering
2. Geoengineering and Solar Radiation Management
3. Solar Radiation Management Geoengineering and Climate Sensitivity
4. Research Needs for Solar Radiation Management (Climate Geoengineering)
5. Geoengineering Potential of Mineral Weathering Schemes