geo-big.jpg I know you’ve all been eagerly waiting for this (don’t worry, I don’t have many more rules). I got sidetracked by last week’s offset hearing.

Offset projects should deliver climate benefits with high confidence — that’s a key reason trees make lousy offsets, especially non-urban, non-tropical trees. An even more dubious source of offsets is geo-engineering, which is “the intentional large scale manipulation of the global environment” (PDF) to counteract the effects of global warming.

As John Holdren, President of the American Association for the Advancement of Science, noted in 2006 (PDF), “The ‘geo-engineering’ approaches considered so far appear to be afflicted with some combination of high costs, low leverage, and a high likelihood of serious side effects.

The only reason for this rule is that a company, Planktos, wants to sell offset credits for carbon that is supposedly sequestered when iron is seeded in the ocean to create algae blooms. Seriously. (This is the same company that is selling trees as offsets to the Vatican.)

Grist thanks its sponsors. Become one.

This is such a dubious idea that 18 leading experts from 13 countries, who comprise the Scientific Steering Committee of the Surface Ocean-Lower Atmosphere Study (SOLAS) — a lead-in group studying the ocean-atmosphere system — went to the trouble of issuing a “Position Statement on Large-Scale Ocean Fertilisation” last month:

Large-scale fertilisation of the ocean is being actively promoted by various commercial organisations as a strategy to reduce atmospheric CO2 levels. However, the current scientific evidence indicates that this will not significantly increase carbon transfer into the deep ocean or lower atmospheric CO2. Furthermore, there may be negative impacts of iron fertilization including dissolved oxygen depletion, altered trace gas emissions that affect climate and air quality, changes in biodiversity, and decreased productivity in other oceanic regions. It is then critical and essential that robust and independent scientific verification is undertaken before large-scale fertilisation is considered. Given our present lack of knowledge, the judgement of the SOLAS SSC is that ocean fertilisation will be ineffective and potentially deleterious, and should not be used as a strategy for offsetting CO2 emissions.

Grist thanks its sponsors. Become one.


In 2001, ocean scientists Sallie Chisholm, Paul Falkowski, and John Cullen wrote an article in Science, “Dis-Crediting Ocean Fertilization” (sub. req’d). They point out the leakage problem:

Despite the claims of the proponents, carbon sequestration from ocean fertilization is not easily verified. Besides measuring carbon flux profiles and comparing them with a control basin, one would have to determine what fraction of the natural stores of N [nitrogen] and P [phosphorus] used up in the fertilized patch would no longer be available for phytoplankton growth in downstream ocean regions. This would require complex numerical models of large-scale ocean physics and biogeochemistry, the predictions of which cannot be validated through small perturbations such as patch fertilizations.

They also note that while “no single application” of small-scale fertilizations subsidized by carbon credits “would cause sustained ecosystem damage”:

But if it is profitable for one, it would be profitable for many, and the cumulative effects of many such implementations would result in large-scale consequences — a classic “tragedy of the commons.”

One simple way to avert this potential tragedy is to remove the profit incentive for manipulation of the ocean commons. We suggest that ocean fertilization, in the open seas or territorial waters, should never become eligible for carbon credits.

Double ouch.

We may some day need to pursue geo-engineering, but (1) only after we have exhausted every plausible mitigation strategy, and (2) only after we have done rigorous, small-scale experiments to prove its safety and effectiveness. But geo-engineering projects should certainly not be sold to the public any time soon as carbon offsets.

This post was created for, a project of the Center for American Progress Action Fund.