Make no mistake, despite the sometimes far-fetched proposals, this is not a subject that should be taken lightly. As Chairman Gordon has also made clear: geoengineering has been proposed as—and it can only be responsibly discussed as—a last-ditch measure in the case that traditional carbon mitigation efforts prove ineffective on their own. Even then, a tremendous amount of research is required to know what strategies may be worth deploying.

—Chairman Brian Baird (D-WA)

Members questioned witnesses about the science, engineering needs, environmental impacts, price, efficacy, and permanence of select geoengineering proposals.

Geoengineering strategies fall into two major categories: Solar Radiation Management and Carbon Dioxide Removal. Solar Radiation Management techniques aim to reflect a portion of the sun’s radiation back into space, thereby reducing the amount of solar radiation trapped in Earth’s atmosphere. Types of Solar Radiation Management include: installing reflective surfaces in space; and increasing reflectivity of natural surfaces, built structures, and the atmosphere. Carbon Dioxide Removal aims to reduce excess carbon dioxide concentrations by capturing carbon directly from air and storing it. Carbon Dioxide Removal proposals include such methods as carbon sequestration in biomass and soils, ocean fertilization, modified ocean circulation, non-traditional carbon capture and sequestration in geologic formations, and distributing mined minerals over agricultural soils, among others.

Some Solar Radiation Management approaches could be quickly deployed at a relatively low cost and shut down if necessary. Witnesses discussed the low cost as a potential risk in itself, because nations, corporations, or individuals could act unilaterally.

Neither Solar Radiation Management nor Carbon Dioxide Removal techniques would eliminate all climate change effects. For example, Solar Radiation Management could block solar radiation, but ocean acidification, the change in ocean chemistry caused when ocean water absorbs excess carbon dioxide, would continue unabated. Ocean acidification reduces the ability of shellfish and corals to form their shells and skeletons, which impacts the health of the entire ocean food chain.

Witnesses also strongly emphasized that any type of intervention may carry significant unintended and unknown consequences for ocean ecosystems, agriculture, and the built environment. They emphasized the need for more research to understand potential consequences.

This hearing was the second of a three-part series on geoengineering in the Committee on Science and Technology. The series is intended to create the foundation for an informed and open dialogue on the science and engineering of geoengineering. The Full Committee held the first hearing on November 5, 2009, entitled Geoengineering: Assessing the Implications of Large-Scale Climate Intervention. The third hearing is planned for spring 2010 and will cover issues of governance.

The series of hearings is part of a partnership with the United Kingdom House of Commons Science and Technology Committee. The two Committees are holding parallel hearings and sharing materials once they are publicly available. The Commons Committee’s hearings and requests for information focus on the domestic and international regulatory frameworks that may be applicable to geoengineering.

Resources

• Geoengineering II: The Scientific Basis and Engineering Challenges