'We need, at the minimum, a serious long-term exploratory research effort to develop air capture along with other direct methods for removing CO2 from the atmosphere,'' he adds.

According to Keith, air capture technology also offers the possibility of turning the captured carbon dioxide into carbon-neutral synthetic fuels for vehicles, to reduce vehicle emissions.

Air capture plants also might be built where the costs of construction and operation are cheap, and near the best sites for permanently storing the captured carbon dioxide underground, he says.

For the short term, he advocates efforts to limit the risks of climate change by focusing on reducing industrial and other sources of carbon emissions.For the long term, he says air capture technology offers a way to reduce carbon dioxide concentrations in the atmosphere, to manage otherwise irreversible risks of climate change.