The New York Times, among others, is reporting that a private entrepreneur dumped 100 tons of iron dust off the shore of western Canada this summer, in an attempt to influence the local climate. The idea goes that iron stimulates growth of plankton, who take up carbon dioxide locally, and then die and sink to the bottom of the ocean — carbon trapped! Planet saved! Well, things aren’t quite that simple.
Certain swaths of the ocean are ripe for plankton growth, just limited by trace nutrients. In fact, if you add iron to these parts of the ocean, you can get a large bloom of phytoplankton in the shallow ocean, and they do take up a lot of carbon dioxide locally. Then they die and are eaten by other microorganisms (the bigger microorganisms eat the littler ones — just like fish), who re-emit carbon dioxide and methane, another greenhouse gas. That sort of negates the effect of the phytoplankton at the surface. The trick is, iron fertilization only works to sequester carbon if you can get it to settle out to the bottom of the ocean, which is rather deep. Like 4,000 meters / 12,000 feet deep. It’s really hard to get biomass to sink past ~200 meters. In the natural cycle of things, only roughly 20-30% of the biomass in the shallow ocean makes it to the deep ocean.
Actual iron fertilization experiments have had very mixed results, with most of them showing evidence of more rapid biomass cycling in the shallow ocean, but little evidence for significant burial at depth. The response also depends strongly on the specific location that is fertilized (all parts of the ocean are not the same).
So this entrepreneur got tired of the wishy-washiness of scientists and politicians, and took matters into his own hands, apparently at the invitation of a native American population that wanted to stimulate their salmon population. He would like to start a company to dump iron in the ocean to get carbon credits from emissions trading schemes, but if the carbon isn’t actually buried in the deep sea, he shouldn’t be getting any carbon credits (= money) for his work! Plus, in light of the mixed results of the science, politicians decided not to allow any further experimentation under ocean dumping agreements — the London Convention and the UN Convention on Biological Diversity.
I don’t know what the results will show, as far as the fish are concerned, but to conduct “experiments” on this scale is reckless and sets a dangerous precedent. What if some rogue decides to “geoengineer” the climate based on pseudo-science and causes a massive disaster? There’s a reason why geoengineering hasn’t been adopted yet — it hasn’t been proven yet on a pilot-scale! Aerosols like sulfate will cause acid rain, iron might just cycle carbon faster in the shallow ocean without any long-term burial, and carbon capture and sequestration may leak significantly…When science finds that silver bullet for climate change, we will let you know.