Wallace Broecker, of Columbia University's Lamont-Doherty Earth Observatory, first warned in the 1970s that the earth would warm because of a buildup of carbon dioxide and other gases released by burning fossil fuels. In his new book, Fixing Climate (co-authored by Robert Kunzig), Broecker, 76, argues that we must not only reduce emissions of carbon dioxide (CO₂) but also remove it from the atmosphere on a massive scale to avert environmental ruin. He is an unpaid adviser to Global Research Technologies, a Tucson firm developing devices to capture CO₂ from the air.

Looking at the earth's past climate told me that the earth is very sensitive to changes. It concerned me that as we warmed the planet we were heading into unknown territory. I've convinced myself that it is going to be absolutely necessary to capture and bury CO₂.