John Holdren, in his first interview since appointed as Obama’s new science adviser, revealed earlier this month that “global warming is so dire, the Obama administration is discussing radical technologies to cool Earth’s air.” So is he a crack pot or does what he say make sense?
It might sound like science fiction, but Holdren elaborated, “as an experimental measure [the plan] would only be used as a last resort … It’s got to be looked at … We don’t have the luxury of taking any approach off the table … One such extreme option includes shooting pollution particles into the upper atmosphere to reflect the sun’s ray.”
Holdren compared the way humanity is facing dangerous climate change to passengers in a car with bad brakes heading toward a cliff in a fog, saying “The sensible passengers will certainly say: ‘Let’s put on the brakes, even if we don’t know it will save us. It may be too late. We don’t know exactly where the cliff is … Let’s get on with it.'”
But Holdren is not alone in considering geoengineering. The National Academy of Science is also looking at the subject in its new multidiscipline climate challenges program. And the American Meteorological Society is preparing a statement on geoengineering, stating “it is prudent to consider geoengineering’s potential, to understand its limits and to avoid rash deployment.” The British parliament has also discussed the idea.
But pro-environment people are concerned attempts at geoengineering would incur a multitude of predictable and unpredictable side effects (collateral damage), and decrease the pressure on governments and industry to reduce carbon emissions.
Climate geoengineering scenarios fall into at least four principal categories:
- Increased reflectivity (albedo) of the atmosphere, injecting sulphur dioxide, as suggested by Paul Crutzen, the Nobel Prize winner atmospheric chemist, or alumina particles, or even installing reflectors in space. The effects of Sulphur injections would simulate volcanic events, such as of Pinatubo (1991) or Tambora (1816), which resulted in cooling of the Earth surface by about 0.5 degrees. A principal concern is the consequent increased acidification of the oceans and slow-down of the hydrological cycle.
- Increased sequestration of CO2 in the oceans, enhancing algal blooms, phytoplankton and photosynthesis through fertilization with iron filings (iron being a limiting growth factor of marine algae), or constructing vertical pipe systems designed to enhance oceanic circulation and CO2 intake from the atmosphere.
- Biochar burial and soil enrichment. Combustion of plant waste under low oxygen conditions and burial as charcoal, removing carbon from atmospheric circulation and enhancing plant growth and photosynthesis, as well as soil enrichment. A major controversy erupted with objections to Biochar by George Monbiot, who questioned favourable references to this method by James Lovelock and James Hansen.
- CO2 draw-down involving capture of the gas by sodium hydroxide (NaOH) pipe systems (“Sodium trees”), followed by separation and burial of CO2, costed at about $US300 per-ton CO2.
A back of an envelope calculation suggests the reduction of atmospheric CO2 by 50 ppm would cost about $US10 — 15 trillion, although mass production may lessen the cost as well as contribute to employment. This is less than 10 years of military expenditure ($1100 billion in 2007).