'Carbon Pie' to Curb Global Warming?

March 8, 2007 — If the world wants to get serious about cutting carbon emissions and controlling global warming, we need to divvy up an international carbon pie, says one researcher.

Such a pie, which would set an upper limit on carbon greenhouse emissions per person worldwide, would allow some poorer countries to sell pieces to richer nations, which emit more carbon per capita.

"Unless you constrain the amount (of fossil fuels) that can be burned, you're never going to bring carbon dioxide down," regardless of how much energy conservation and fuel efficiency we achieve, said researcher Wallace Broecker of Columbia University's Lamont-Doherty Earth Observatory. He published his strategy in the March 9 issue of the journal Science.

"I'm not saying for a minute that we don't need all those things," Broecker told Discovery News. "But they will fall short."

That means we will be stuck with a warmer world for centuries — which will be enough time to melt Greenland's ice and raise sea level several meters, he said.

"During the last interglacial (the warm period before the last Ice Age), sea level stood six to seven meters higher than today," said Broecker. That could easily happen again if we don't cut carbon emissions immediately, he added.

Broecker believes the carbon pie approach would make it easier to cut emissions by setting an upper limit to the total amount of carbon added by humans to the atmosphere.

Right now humans burn and release about four gigatons of carbon into the air each year. Another four gigatons is released by wildfires. That raises the carbon dioxide concentration in the atmosphere by about one part per million (ppm) every year.

If a carbon dioxide cap were set at 560 ppm worldwide — twice the pre-industrial levels — there would be a carbon pie of 720 gigatons to divvy up. A lower ppm goal, about 450 ppm, would reduce carbon dioxide even further and shrink the carbon emissions pie to 280 gigatons.

But such a reduction would be possible only with successful efforts to actively take more carbon out of the atmosphere, said Broecker. That means new technologies to suck up the carbon dioxide, which can then be pumped into the ground.

"The hardest thing is direct capture" of carbon dioxide, said climate researcher David Keith of the University of Calgary. Research into the matter is very preliminary, he said, and ultimately comes down to the problem of making it cost-effective.

"Air capture is certainly technically possible," said Keith. "But can you do it at a reasonable cost?"

As for whether Broecker's carbon pie strategy will ever be implemented, that's a political question, Keith said.

"We don't know the politics yet," said Keith. "It may take a hundred years to figure this out."