During a speech yesterday in Washington that commemorated the 20 years since his declaration to the Senate that global warming had already begun, Jim Hansen, Director of the NASA Goddard Institute for Space Studies, spoke out about cutting the level of carbon dioxide emitted into the atmosphere. Hansen argued that in order to stabilize the world's climate, the US must cut carbon dioxide emissions to 350 parts per million. This is 30 percent lower than a Senate bill that calls for a cap at 450 ppm, and lower than our current output of 385 ppm.

"I have greater than 99% confidence—99.9% confidence—that the dangerous level is no higher than 350 ppm, and that means we've already passed it," Hansen said.

Hansen called for a "zero-carbon society" and proposed a plan to limit emissions. Under his plan, oil, gas, coal, and other fossil fuels would be taxed at the point of sale. Proceeds would be distributed in dividend payments to individuals, which would encourage the sale of low-carbon cars, among other products.

In response to the recent talk about offshore drilling and expanded American oil production, Hansen was adamant that it is "exactly the wrong thing to do." He said that while short-term gains may be made, they would only continue to damage climate health in the long-term.

"It just extends your addiction slightly and guarantees we'll go past the tipping point of irreversible climate change," he says.