DURHAM, N.C. – When Presidential science advisor John Holden said last August that he wouldn’t rule out engineering Earth’s climate as an option to slow global warming, it sparked political and scientific debate about the perils – and practicality – of intentionally modifying the planet’s climate on a large scale.

Duke University environmental scientist Robert B. Jackson will present testimony about the controversial strategy to the U.S. House Subcommittee on Energy and Environment at 10 a.m. Thursday, Feb. 4, in room 2318 of the Rayburn House Office Building.

“Geoengineering sounds like science fiction. But it’s more and more likely, if we won’t slow fossil fuel emissions by other means,” says Jackson, Nicholas Professor of Global Environmental Change and Professor of Biology at Duke. “Countries have tried for years to control weather in smaller-scale versions, like seeding for rain, with mixed success.”

There are two basic types of geoengineering, Jackson will explain. Strategies that try to remove carbon dioxide from Earth’s atmosphere, reducing greenhouse gas concentrations directly, fall into the first category. Some of these, including forest restoration and biological carbon sequestration through plants and soils, are more feasible today, Jackson will tell the subcommittee, though further research is needed on their full effects.

The second category of geoengineering includes strategies to reduce the harmful symptoms of climate change, particularly rising temperatures. Strategies in this category, such as injecting dust into the atmosphere to block sunlight, require much more research before we proceed.

“We have to be sure our efforts to engineer the climate make things better, not worse,” Jackson says. “Geoengineering may help treat symptoms of climate change but alter water resources, biodiversity and other things people value. We need to get this right.”

The Feb. 4 subcommittee hearing is the second in a series of three on geoengineering. Testimony from the series will contribute to a future joint report with the United Kingdom’s House of Commons’ Committee on Science and Technology.

Jackson, an expert on global environmental change, organized a geoengineering symposium at the 2009 annual meeting of the Ecological Society of America. He is director of Duke’s Center on Global Change.