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Geo-engineering cause, not cure

Olive Heffernan

In Correspondence in this week’s Nature, John Shepherd from the National Oceanography Centre, Southampton and colleagues challenge the scheme proposed by James Lovelock and Chris Rapley to help the planet cure itself from the disease of global warming.

For those of you who missed it, a couple of weeks ago, Lovelock and Rapley put forward a geo-engineering solution to climate change in Nature, which involves the installation of large vertical pipes in the ocean that would pump nutrient-rich water from depth to the surface. This, they said, would enhance the growth of algae in the upper ocean, which in turn would transport more carbon to the deep sea.

Now, Shepherd and colleagues claim that the proposed scheme is based on false assumptions. They say the scheme would not lead to enhanced storage of carbon in the deep ocean below 1,000m and in deep ocean sediments, which is necessary for effective long term removal of carbon from the atmosphere. Instead, they maintain the scheme could actually worsen global warming by bringing high levels of particulate carbon back to the surface, where it could be released to the atmosphere. The authors also argue that such large scale engineering solutions could harm fragile ecosystems.

Peter Williams from the School of Ocean Sciences at Bangor University raised some of these same issues on the blog here last week, and also challenged the feasibility of the scheme from an engineering perspective.

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    David Blair said:

    In order to find the cure you know the sickness. Treating the symptoms is not as good as treating the illness. There is little chance of a Panacea. I thought Lovelock claimed the situation was irreversible. The problem with Lovelock is he takes his analogies to literally.

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    Russell Seitz said:

    Last week’s nature leader (1) remarked that “Data…that are not gathered today can never be gathered in the future” applies equally to things that while they no longer go into the ocean, may help determine marine policy for generations to come.

    John Martin launched the ocean fertilization controversy two decades ago (2) by asserting : “Give me a half tanker of iron and I’ll give you an ice age.” Fears of oil spill impacts on food webs make marine biologists skeptical of current proposals to capture carbon by fertilizing the oceans, yet It appears that the late Dr.Martin got his wish before he was born, with hundreds of thousands of tonnes of finely divided iron iron compounds—the equivalent of many shiploads—being dispersed at sea annually.

    The biogeochemical cycle of iron continues today with the wind-born deposit of tonnes of metal bearing dust far out to sea. It is therefore relevant to todays ’geoengineering ’ debate that changes in 20th century shipping practice may have altered the marine biochemical equilibrium, for the period from 1900 to 1950 saw a radical decline in anthropogenic iron deposition in mid ocean waters as oil replaced coal as the dominant marine fuel.

    Coal combustion in large boilers typically generates ash equal to ~10 % of the fuel mass. In modern combustion technology, electrostatic precipitators, baghouses, and scrubbers remove over 95% of particulates. Though mandatory today, no effort was made to capture fly ash in early coal-fired marine propulsion, and approximately three fourths was entrained and released with hot flue gases, only the coarser particulates being caught in stacks or incorporated into boiler slag and scoria (3)

    A 50,000,000 ton fleet of such coal burning ships operated early in the 20th century(4). Owing to the low energy density of coal relative to oil, its annual coal consumption often exceeded its registered tonnage. While the highly efficient , if ill fated Titanic consumed 1.5% of its 42,000 tonne displacement daily, ordinary vessels of the period typically combusted their displacement in bunker coal in less than 50 days underway. This created enormous marine fuel demand. Europe’s 1913 export of 213 million tons of bunker coal represented less than half the world total (5)

    Coal ash typically contains from 2.5% to 8.5% iron (6). Much represents the oxidation of pyrites( FeS2), and coproduction of SO2 during combustion may enhance the bioavailability of fly ash iron by converting finely divided iron oxides into sulfates.

    With on the order of a Teragram of iron being released and dispersed at sea annually in the early 20th century, ( range .39 to 2.16 TG) frequent replenishment of the aerosol iron flux along heavily traveled shipping lanes may have assured phytoplankton in mineral deficient ’marine desert ’ regions a continuous ancillary supply of the iron m=necessary for metabolism and growth.Studying the quantities and composition of coal combusted along historic shipping lanes may accordingly shed light on the risks and benefits of smaller CO2 sequestration experiments today, and even illuminate why 20th century climate falls near the low end of many model estimates of radiative forcing .(6)

    (1)Patching together a world view, 2007 Nature 450, 761

    (2)Martin, J. H., K. H. Coale, K. S. Johnson, S. E. Fitzwater, et al. 1994: Testing the Iron Hypothesis in Ecosystems of the Equatorial Pacific Ocean. Nature, 371, 123-129.

    (3) https://www.EPA.gov/rpdweb00/tenorm/coalandcoalash.html

    (4) LLOYDS REGISTER , https://www.coltoncompany.com/shipping/statistics/wldflt.htm

    (5)J. F. Bogardus Geographical Review, 1930, 20, 4. pp. 642-651

    (6) S. K. Gupta, T. F. Wall, R. A. Creelman and R. P. Gupta 1998, Fuel Processing Technology 56, 1-2 Pages 33-43

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    tony lovell said:

    Soil Carbon – helping to reverse global warming, desertification and biodiversity loss

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