The rapid pace of global warming is driving worldwide efforts to shore up the primary culprit, carbon dioxide. One particular technology, pioneered by scientists at Moss Landing Marine Laboratories, may be the closest we’ve come to a free lunch – with the potential to suck hundreds of millions of tons of CO2 from the atmosphere every year.

Ocean iron fertilization (OIF) involves dumping iron in the sea to boost the production of phytoplankton, which sponges carbon dioxide from the atmosphere. But scientists don’t fully understand how large-scale OIF would impact marine ecosystems, or even whether it would effectively mitigate global warming.

As companies position themselves to profit from OIF, some of the local scientists who conducted the first OIF experiments are sounding a cautionary note. In the Jan. 11 issue of Science, 15 scientists – including MLML Director Kenneth Coale and Monterey Bay Aquarium Research Institute scientist Ken Johnson – argue that it’s too soon for the private sector to start seeding iron for profit.

Carbon offsets are the new currency for carbon dioxide reduction. In countries that have signed onto the Kyoto Protocol, companies and agencies may buy offsets to lower their net CO2 emissions to permitted levels. In the United States, which has not ratified Kyoto, people may voluntarily buy carbon credits to “neutralize” their own emissions. (Google recently announced it’s going carbon neutral, in part by purchasing carbon offsets.) The Lieberman-Warner Climate Security Act, currently before Congress, would regulate carbon dioxide emissions with a Kyoto-style cap-and-trade system.

That means big money for companies that can remove CO2 from the atmosphere – often by planting trees. The 2006 compliance and voluntary markets in carbon offsets totaled about $6.4 billion.

Cue Climos, a two-year-old San Francisco venture that hopes to sell carbon offsets for OIF. “If we can store carbon, the world will pay us to do it,” says company co-founder Dan Whaley.

Another Bay Area enterprise, Planktos, planned a massive dump of iron particles near the Galapagos Islands. But in mid-February the company announced that it was “forced to indefinitely postpone” its OIF projects, likely because of pressure from activists and reservations from the U.S. and Ecuadorian governments. Six weeks later, the company founder and CEO resigned. Planktos managers were not available to comment.

The authors of the Science paper argue that regulators shouldn’t let private companies sell carbon offsets for OIF until they have more independent data. Scientists don’t yet know how long it takes for OIF to remove carbon from the atmosphere, or at what rate. The iron could potentially cause toxic diatom blooms, deplete oxygen needed by marine life, impact nutrient availability in other parts of the sea, and spur the production of other powerful greenhouse gases.

“There are legitimate uncertainties that need to be explored before any scientists would be able to recommend ocean fertilization as a responsible option to mitigate atmospheric CO2,” MLML’s Coale says. “We need more data before we turn one environmental calamity into another.”

Coale’s concerns carry a special weight because MLML pioneered the idea of OIF. In the late 1980s, former MLML director John Martin and then-grad student Mike Gordon discovered that adding iron to seawater promotes phytoplankton growth. Martin pursued the idea of using OIF as a way to mitigate global warming, famously quipping at a 1991 seminar, “Give me half a tanker of iron and I’ll give you the next Ice Age.” It was an exaggeration, but it did the job of sparking imaginations – and controversy.

In 1993, after Martin died of prostate cancer, an international team of scientists including Coale and Johnson conducted the first OIF experiment on an unproductive patch of sea southwest of the Galapagos Islands. The iron solution boosted plankton, but at a quarter of the predicted rate. Two years later Coale led a follow-up expedition, and this time the waters exploded with growth.

Another 10 publicly funded experiments have tested OIF, but not explicitly as a means to mitigate global warming. That didn’t stop companies from taking out patents on OIF with an eye on the carbon-offset market. The payoff potential is huge: A pound of iron might cost a dime and sequester 10 tons of carbon, Coale says, fetching roughly $1,000 in the carbon market.

As the private sector’s interest grows, public funding for OIF research shrinks. Big research sponsors like the National Science Foundation “have sort of recoiled from this topic and believe it’s in the private sector’s domain,” Coale says.

While the NSF funds a number of investigations into the role of iron in ocean ecosystems, “the goal of it hasn’t been to evaluate the effectiveness or wisdom of using iron to sequester carbon from the atmosphere,” says Phillip Taylor, who heads NSF’s ocean section.

“I don’t think the federal government is interested in funding research that would lead to carbon credits,” MBARI’s Johnson says. “NSF isn’t going to do it because it’s not the sort of stuff they do, and [the U.S. Department of Energy] won’t do it because they haven’t decided if this is in their purview.”

Yet public funding is critical, from Coale’s perspective. “We believe this needs to be investigated fully as a scientific pursuit – an effort on the scale of the Manhattan Project,” he says. “It’s important that we develop a stronger ethic toward science-based Earth stewardship, because economic-based stewardship doesn’t necessarily serve the planet.”

Whaley disagrees. “People in the science and environmental communities are so suspicious, partly because they see business as being part of the problem,” he says. “That’s understandable, but to some degree it’s not a constructive point of view. This can be approached in a commercial framework which is responsible.”