Did you notice that President Obama didn’t say the words “climate change” or global warming” in his 7,000-word State of the Union speech? He described government support for clean energy as

an investment that will strengthen our security, protect our planet, and create countless new jobs for our people

Partly this is repackaging, and not in a good way.  Partly it’s a recognition that we’re utterly failing, here in the U.S. and globally, to curb the greenhouse gas emissions that cause global warming. (See the chart at the end of this blogpost.) That’s not something the president wants people to think about. It’s actually not something that anyone wants to think about–not environmentalists, because it leads to a sense of hopelessness, not free-market ideologues, because it’s a glaring example of market failure, not the press because, well, climate change has become an old and depressing story,.

But ignoring the threat of climate catastrophe won’t make it disappear.

So, sooner or later, as people come to see the threat, scientific and political attention will turn to geoengineering—deliberate intervention in the climate system to moderate global warming. By coincidence, on the day after the president spoke, scientists at UNESCO published a guide to one of the early approaches to geoengineering, a technique known as ocean fertilization or iron fertilization. The idea here is that  sprinkling iron dust atop the oceans will stimulate plant growth and suck large quantities of carbon dioxide out of the air.

Ocean fertilization has been bruited about for decades. “Give me a half tanker of iron, and I will give you an ice age,” a scientist named John Martin said back in the 1980s. The technique attracted some notoriety more recently when a couple of U.S-based startup companies, Climos and Planktos, were created to explore the idea. (I wrote about Climos for Fortune.com in 2008.)

Unfortunately for advocates of ocean fertilization, UNESCO’s 20-page report delivers mostly discouraging news.  To begin with–and this is no surprise–it says that the effects of tinkering with the ocean’s chemistry are largely unknown:

Large-scale fertilization could have unintended (and difficult to predict) impacts not only locally, e.g. risk of toxic algal blooms, but also far removed in space and time.

Impact assessments need to include the possibility of such ‘far-field’ effects on biological productivity, sub-surface oxygen levels, biogas production and ocean acidification.

But you knew that. Hacking the planet is risky business.

More significant, though, is the report’s conclusion that ocean fertilization will not prove to be a very effective way to combat climate change:

Estimates of the overall efficiency of atmospheric CO2 uptake in response to iron-based ocean fertilization have decreased greatly (by 5 – 20 times) over the past 20 years. Although uncertainties still remain, the amount of carbon that might be taken out of circulation through this technique on a long-term basis (decades to centuries) would seem small in comparison to fossil-fuel emissions.

One of the problems is that only a small fraction of the carbon drawn out of the atmosphere sinks to depths of the ocean and is therefore removed from the carbon cycles.

Bummer.

Estimating the amount of carbon that would be sequestered in the ocean requires making a bunch of assumptions but the report says

even using the highest estimates for both carbon export ratios and atmospheric uptake efficiencies, the overall potential for ocean fertilization to remove CO2 from the atmosphere is relatively small. Thus recent calculations of cumulative sequestration for massive fertilization effort over 100 years are in the range 25-75 Gt (gigatonnes) of carbon, in comparison to cumulative emissions of around 1,500 Gt carbon from fossil fuel burning for the same period under business-as-usual scenarios.

Research into ocean fertilization will surely continue. A company in Bangalore, India, is marketing a product called Nualgi that it says causes algae to bloom, absorbing CO2, releasing oxygen and providing food for fish.

Meanwhile, the Scripps Institution of Oceanography will host a seminar of geoengineering tomorrow (Monday, Jan. 31) that is organized by a global research group called the International Geosphere-Biosphere Programme (IGBP). It’ll be steamed live here.

The IGBP, as it happens, has created a “Climate-Change Index” to track key indicators of global change: atmospheric carbon dioxide, temperature, sea level and sea ice. The index provides an annual snapshot of how the planet’s complex systems – the ice, the oceans, the land surface and the atmosphere – are responding to the changing climate. As you can see (please click on the image for a clearer view), the index has been rising steadily since 1980, the earliest date for which it has been calculated.

 

IGBP Climate Index