One method of removing carbon dioxide from the atmosphere involves phytoplankton: they remove CO2 through photosynthesis. An experiment was conducted in the southwest Atlantic ocean to provide additional iron to phytoplankton, which use it to grow, in order to remove more CO2 than usual. The idea being if enough phytoplankton can be encouraged to grow (over a large enough area and given enough time), the phytoplankton would eventually die off and sink to the bottom of the ocean, taking their ingested CO2 with them. They would act as a sort of super-charged carbon sink. Unfortunately, things didn’t quite work out the way the experimenters had hoped (I had to edit some of the article – I thought journalists had higher standards than bloggers):
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 amphipods. As the carbon moved up the food chain some of [it] 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.
Such is the role of science: test a theory to see how robust it is. In this case, the outcome didn’t match expectations. Be that as it may, I prefer solutions that reduce the amount of CO2 emissions going into the atmosphere in the first place. I think geo-engineering concepts are potentially dangerous. After all, emissions of GHGs is really a big geo-engineering project and we’re finding out just how extensive our activities really are, aren’t we?