Will Iron-Fertilisation of the Oceans Work?
The whole concept of iron-fertilisation of the oceans rests upon the idea that expected increased populations of phytoplankton draw increased amounts of CO2 from the atmosphere, and somehow sequester it, so removing it from the carbon cycle for the long term.
Although it has been categorically proved that iron enrichment of water increased photoplankton production, whether that will necessarily lead to increased carbon sequestration has not been shown. There are a large number of unknowns, including:
- No-one really knows how much, if any, of the increased organic carbon gets sequestered in the deep ocean floor, and how much returns to the surface. Increasing phytoplankton may lead to only temporary storage at best, at an unacceptable risk.
- What was the source of the iron in the geological record that (possibly) led to global cooling? Was it wind blown onto the ocean surface, or did it upwell from the ocean floor?
If the iron upwelled, then it may have had a longer residence time in the surface waters than has air-bourne dust, so may have been able to support prolonged blooms. So far, all experimental and natural-dust event blooms have been short-lived. This is covered in detail under "Upwelling Iron" in 'Evidence'
- Solar reflection. Some claim that as some species of phytoplankton absorb solar radiation, which would otherwise be reflected back out of the Earth's atmosphere, the world would be cooler without phytoplankton; and that an increase in phytoplankton could contribute to global warming. (detail below)
Solar Reflection
Research by the Shripps Institution of Oceanography has questioned the premise that increased phytoplankton will necessarily lead to global cooling.
'They have shown that some species of phytoplankton absorb solar radiation, which would otherwise be reflected back out of the Earth's atmosphere. Phytoplankton may thus decrease the Earth's albedo.
Temperature-detection satellite images show that oceans teeming with phytoplankton are between 0.1 to 0.6oC warmer than they would otherwise be, so an increase in phytoplankton could lead to increased temperatures.
Figures indicate that the warming effect of phytoplankton is about 20% that of all the anthropogenic greenhouse gases released since pre-industrial times. Without phytoplankton, the world would be cooler.
Thus, phytoplankton exert a significant and previously uncalculated influence on Earth's climate, and any attempt to increase phytoplankton may have the exact reverse effect that is intended.' [1]
Export Calculations
Refs:
[1] http://scrippsnews.ucsd.edu/pressreleases/frouin_phytoplankton.cfm
"Scripps Research Gives Tiny Phytoplankton a Large Role in Earth’s Climate System"
Press Release, November 6, 2002
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