Use smoke, mirrors to combat global warming?

A private company is already carrying out what could be dubbed the Geritol plan. Some scientists call it promising while others worry about the ecological fallout.

Planktos Inc., of Foster City, Calif., last week launched its ship, the Weatherbird II, on a trip to the Pacific Ocean to dump 50 tons of iron dust. The iron should grow plankton, part of an algae bloom that will drink up carbon dioxide from the atmosphere.

The idea of seeding the ocean with iron to beef up a natural plankton and algae system has been tried on a small scale several times since 1990. It has both succeeded and failed.

Planktos chief executive officer Russ George said his ship will try it on a larger scale, dumping a slurry of water and red iron dust from a hose into the sea.

“It makes a 25-foot swath of bright red for a very short period of time,” George said.

The concept gained some credibility when it was mentioned in the 2001 report by the authoritative Intergovernmental Panel on Climate Change, which cited it as a possible way to attack carbon emissions.

Small experiments “showed unequivocally that there was a biological response to the addition of the iron,” the climate report said. Plankton used the iron to photosynthesize, extract greenhouse gases from the air, and grow rapidly. It forms a thick green soup of all sorts of carbon dioxide-sucking algae, which sea life feast on, and the carbon drops into the ocean.

However, the international climate report also cautioned about “the ecological consequences of large-scale fertilization of the ocean.”

Tim Barnett, a marine physicist at the Scripps Institution of Oceanography, said large-scale ocean seeding could change the crucial temperature difference between the sea surface and deeper waters and have a dramatic effect on marine life.

Cicerone, a climate scientist who is president of the National Academy of Sciences and advocate for more geoengineering research, said that while the method has led to some promising science, he believes it is unlikely to be an effective way of removing significant amounts of carbon dioxide from the air.

Planktos Inc. via AP Planktos Inc. uses this ship to experiment with dumping tons of iron dust into the ocean. The iron should grow plankton, part of an algae bloom that will drink up carbon dioxide from the atmosphere.

George, Planktos’ CEO, said his company consulted with governments around the world and is only following previous scientific research. He said his firm will be dropping the iron in open international seas so he needs no permits. Most important, he said, is that it’s such a small amount of iron compared to the ocean volume that it poses no threat.

He said it’s unfair to lump his plan in with geoengineering, saying his company is just trying to restore the ocean to “a more ecologically normal and balanced state.”

“We’re a green solution,” George said.

Planktos officials say that for every ton of iron used, 100,000 tons of carbon will be pulled into the ocean. Eventually, if this first large-scale test works, George hopes that he and other can remove 3 billion tons of carbon from the Earth’s atmosphere, half of what’s needed. Some scientists say that’s overstated.

Planktos’ efforts are financed by companies and individuals who buy carbon credits to offset their use of fossil fuels.

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