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It's ALL THINGS CONSIDERED from NPR News. I'm Audie Cornish.
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And I'm Robert Siegel. A noted oceanographer once quipped, give me a half tanker of iron and I will give you an ice age. He was only half joking. Adding iron to the ocean can cause blooms of algae. They have the potential to take huge amounts of carbon dioxide out of the air and, by so doing, cool the planet. Well, that's the theory, at least.
NPR's Richard Harris reports on the long-awaited results of a study that tried it out.
RICHARD HARRIS, BYLINE: The premise of this experiment is that algae growing in the oceans around Antarctica can't grow fast because it's starved of an essential nutrient - iron. Victor Smetacek at the Alfred Wegener Institute for Polar and Marine Research in Germany says iron there is as precious as water is for plants on the land.
VICTOR SMETACEK: Where you have heavy rainfall, you have forests and where there is no rainfall, you have deserts. And you have the same thing with iron falling from the atmosphere on the ocean.
HARRIS: Thirty years ago, scientists started wondering if they could create huge blooms of algae in the oceans by adding iron. In concept, the algae would also soak up huge amounts of carbon, carbon that's in the air and in the ocean as a result of our burning fossil fuels. Sending carbon to the sea floor could slow global warming.
So, Smetacek and his colleagues went to sea in 2004 to make algae blooms by adding iron to the water.
SMETACEK: Previous experiments showed was that you added the iron. you got a big algae bloom, but they were not able to show what happened to the bloom.
HARRIS: So, on his expedition, the scientists found a place in the southern ocean where swirling currents created a natural container for their experiment. Their research vessel sprinkled iron into the water and stayed there for four weeks to measure what was happening to the algae that they had fertilized.
Within a few weeks, the algae died and clumped up like snowflakes. Those particles fell down into the deep.
SMETACEK: And we were able to track the particles sinking out of the surface layer all the way down to the sediments.
HARRIS: Down, down through more than two miles of ocean water.
SMETACEK: By the time we left, more than half the bloom had sunk out to the deep and we are confident that the remaining half also sank out, but after we had left.
HARRIS: These results reported in Nature magazine showed that adding iron really can transport substantial amounts of carbon from the surface down to the sea floor. In fact, it did so surprisingly quickly and efficiently and apparently without harming the ecosystem. That's an intriguing finding for people who have been eyeing iron fertilization for the oceans as a way to slow global warming, but Smetacek says, not so fast.
SMETACEK: We need to carry out many more experiments before we should embark on anything like that, before we even talk about anything like that.
HARRIS: And those experiments pretty much ground to a halt a few years ago. A couple of companies swooped into this field hoping to make money by sinking carbon and selling carbon credits and critics started raising concerns.
Lisa Speer at the Natural Resources Defense Council says, what if the process disrupts ecosystems in the ocean? What if it turns out that carbon doesn't stay in the deep?
LISA SPEER: At best, this technology appears to be speculative in terms of its ability to permanently sequester carbon. And, at worst, it could turn out to be a disastrous experiment that could have major impacts on the ocean ecosystems that billions of people rely on for food and for employment and for life itself.
HARRIS: Speer worries that the appeal of what seems to be an easy fix would distract people from doing all the hard work involved in reducing carbon dioxide emissions to begin with. For the moment, that doesn't seem to be an issue. The two companies hoping to capitalize on this have folded.
Ken Buesseler at the Woods Hole Oceanographic Institution argues it's important to keep doing this kind of work, even if you are skeptical about doing it on a grand scale, to deal with global warming. He says these experiments can help explain what's going to happen to the ocean's natural ability to take carbon dioxide out of the air.
KEN BUESSELER: A third of our greenhouse gases we release in the atmosphere, the CO2 ends up in the ocean and will that number increase or decrease as we create a warmer ocean, a more acidic ocean? This type of experiment helps us understand that.
HARRIS: New international rules are now set to allow experiments like this to go forward, but research funding is scarce.
Richard Harris, NPR News.