Discovery.com, April 13, 2009
An ambitious plan to slow global warming by locking CO2 deep in the ocean has hit a stumbling block, according to a new study that shows the geoengineering technique is not as effective as scientists had previously hoped.
"The amount of carbon dioxide that could be taken up is less than we assumed," said Victor Smetacek, a scientist at Alfred Wegener Institute who co-led the expedition. Don't discount ocean fertilization yet however, say scientists working both inside and outside the research study.
"With other climate change initiatives, ocean fertilization could still play a role in reducing climate change, said Smetacek.
The idea behind ocean fertilization is a simple one. Carbon dioxide is slowly raising the average temperature of the Earth. If some of the carbon dioxide in the atmosphere could be removed the Earth wouldn't heat up as fast.
Scientists have come up with a wide variety of plans to remove CO2 from the atmosphere. Some scientists want to pump C02 deep into the underground. Others want to use carbon nanotubes to turn CO2 into methane or other compounds.
Smetacek and his colleagues want to lock up the excess carbon dioxide inside the world's oceans, or more specifically, inside the bodies of microscopic creatures known as plankton, that would die and fall to the bottom of the ocean.
A certain class of plankton, known as phytoplankton, already remove carbon dioxide from the atmosphere through photosynthesis. If there were more phytoplankton, the German and Indian scientists reasoned, then the microscopic creatures would lock away more carbon dioxide.
Phytoplankton need iron to grow. In the open ocean usable iron is difficult to come by, so adding iron to the ocean would lead to more phytoplankton.
Over the course of two and a half months the team of scientists "administered," as Smetacek says, more than six tons of dissolved iron (the kind found in most home improvement stores) over a 300-square-kilometer (116-square-mile) patch of the southwest Atlantic.
The additional iron certainly encouraged more phytoplankton. The amount of biomass in the test area doubled, which scientists determined during marathon 36 hour sampling sessions.
The scientists created more plankton, but the plankton didn't perform as the scientists had hoped. Instead of dying and sinking to the bottom of the ocean, the additional plankton were eaten, first by copepods, then by ampipods. As the carbon moved up the food chain some of was released back into the atmosphere as carbon dioxide.
The scientists concluded that fertilizing the southwest Atlantic was not a good way to lock away carbon dioxide, but that ocean fertilization needs additional testing before it's discounted.
Other oceans and other materials, like silicon instead of iron, might be better candidates for geoengineering, says Ken Buesseler, a scientist at Woods Hole Oceanographic Institute in Massachusetts who has conducted his own ocean fertilization experiments.
"No one is saying that [ocean fertilization] alone will solve the greenhouse gas problem," said Buesseler. "But if we try many different solutions at the same time it could have a significant impact."
Buesseler says that more experiments are necessary to find the best section of the ocean and the best material to encourage plankton to take oxygen out of the atmosphere and to then sink to the bottom of the ocean.
"There is no one solution to solving global warming, said Buesseler, "But doing nothing doesn't seem very satisfying to me."
Agence France-Presse, March 25, 2009
BERLIN (AFP) -- Indian and German scientists have said that a controversial experiment has "dampened hopes" that dumping hundreds of tonnes of dissolved iron in the Southern Ocean can lessen global warming.
The experiment involved "fertilising" a 300-square-kilometre (115-sqare-mile) area of ocean inside the core of an eddy -- an immense rotating column of water -- with six tonnes of dissolved iron.
As expected, this stimulated growth of tiny planktonic algae or phytoplankton, which it was hoped would take out of the atmosphere carbon dioxide, the principal greenhouse gas blamed for climate change, and absorb it.
However, the scientists from India's National Institute of Oceanography (NIO) and Germany's Alfred Wegener Institute (AWI) did not count on these phytoplankton being eaten by tiny crustacean zooplankton.
"The cooperative project Lohafex has yielded new insights on how ocean ecosystems function," an AWI statement published on Monday said.
"But it has dampened hopes on the potential of the Southern Ocean to sequester significant amounts of carbon dioxide (CO2) and thus mitigate global warming."
Earlier projects with iron fertilisation were more successful because they used algae protected by hard shells that do not thrive in the Southern Ocean, the AWI said.
The team set sail from Cape Town on January 7 and spent an "ardous" two ad half months conducting the experiments, buffetted by the treacherous waves of the notorious "Roaring Forties" and twice having to escape approaching storms.
Spicy Indian curries at each meal "contributed to the good atmosphere" however in an "exciting experience laced with the spirit of adventure and haunted by uncertainty quite unlike other scientific cruises," the AWI said.
The experiment is one of several schemes collectively known as geo-engineering which have been getting a closer hearing in recent years in the absence of political progress to roll back the greenhouse gas problem.
But these projects have been heavily criticised by environmentalists for failing to tackle the human behaviour that causes global warming and for having unforeseen and potentially catastrophic consequences.
Other geo-engineering ideas include sowing sulphur particles in the stratosphere to reflect solar radiation and erecting mirrors in orbit that would deflect sunrays and thus slightly cool the planet.
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