Pipe dream

This blog is behind the curve in noting James Lovelock and Chris Rapley's letter to Nature, Ocean pipes could help the Earth to cure itself (see, for example, the BBC story here).

Responses from serious scientists and others seem to have been divided. For example, the felicitously named Quirin Schiermeier at Nature News (Mixing the oceans proposed to reduce global warming, 26 Sep, subscription only) reports a split of views on the likely net effect on atmospheric carbon dioxide concentrations:

"The concept is flawed," says Scott Doney, a marine chemist at [the Woods Hole Oceanographic Institution]. He says it neglects the fact that deeper waters with high nutrients also generally contain a lot of dissolved inorganic carbon, including dissolved CO2. Bringing these waters to the lower pressures of the surface would result in the CO2 bubbling out into the air. So contrary to the desired effect, the scheme could result in a net 'outgassing' of CO2, he warns. "There is no technological fix for this problem," he says.

Others say such a project would have no net effect on CO2 in the atmosphere. "At every meeting I've been to, when they have talked about this idea for surface ocean CO2 removal, the point has been made that you would bring up nutrients and inorganic carbon in the same ratio as you remove as biomass," says Ken Buesseler, a marine chemist at WHOI. And there are potentially many harmful impacts on sea life, he says.

In a BBC video report, Lovelock suggests that the pipes might specifically benefit coral reefs by bringing up cool water to save them. In the same clip John Shepherd, who is one of the most eminent oceanographers in the UK, says the idea may be dangerous, but he is not quoted on specifics, and I have not yet seen in any media an analysis by coral reef specialists of what they think the effects could be. Perhaps they don't think it is worth commenting on (Ove?).

One marine scientist I have talked to says:

This whole crazy scheme is proposed by people with no understanding of marine ecosystems or carbon cycles. Upwelling deep water just causes eutrophication and the algae will kill any coral reefs. Besides almost all the carbon taken up by algae is eaten, or rots, returning the CO2. Almost none is permanently buried, which is the only number that counts. This is the most inefficient possible method of carbon sequestration unless you turn the whole deep sea anoxic and kill all the fish.

P.S. 5 Oct: Oliver Morton hoists some comments from Professor Peter Williams into Nature's climate blog, including:

Even if the engineering problems could be solved, and the system made cost effective, both of which seem very doubtful, the proposal would have the reverse effect of that claimed.