clipped from www.treehugger.com

When the man who coined the phrase "global warming" speaks up, people tend to pay attention. So it was that when Wallace Broecker, a professor at Columbia University, recently called for the use of millions of giant tree-like "scrubbers" (see here for another recent example) to fight global warming, observers didn't immediately dismiss the scheme as harebrained.

The BBC reports that Broecker, addressing a literary festival in the U.K., said that roughly 20 million scrubbers would be needed to suck up all the carbon dioxide produced in the U.S. A grand total of 60 million would be needed worldwide to trap all carbon emissions; he estimated that the entire scheme would cost $600 billion a year -- though how he came up with that figure is unclear. Each scrubber would be 50 ft high and 8 ft in diameter and use a special plastic to capture CO2. The gas could be either pumped underground or liquefied under pressure.