Streetwise Professor

April 13, 2009

The Devil You Think You Know

Filed under: Climate Change — The Professor @ 4:14 pm


New presidential science advisor John Holdren (pictured above) is proposing the use of geo-engineering to counter a potential future catastrophic global warming:

The concept of using technology to purposely cool the climate is called geoengineering. One option raised by Holdren and proposed by a Nobel Prize-winning scientist includes shooting pollution particles into the upper atmosphere to reflect the sun’s rays.

Using such an experimental measure is only being thought of as a last resort, Holdren said.

“It’s got to be looked at,” he said. “We don’t have the luxury … of ruling any approach off the table.”

His concern is that the  United States  and other nations won’t slow global warming fast enough and that several “tipping points” could be fast approaching. Once such milestones are reached, such as complete loss of summer sea ice in the  Arctic,  it increases chances of “really intolerable consequences,” he said.

. . . .  

Holdren, a 1981 winner of a MacArthur Foundation “genius” grant, outlined these possible geoengineering options:

—Shooting sulfur particles (like those produced by power plants and volcanoes, for example) into the upper atmosphere, an idea that gained steam when it was proposed by Nobel laureate  Paul Crutzen  in 2006. It would be “basically mimicking the effect of volcanoes in screening out the incoming sunlight,” Holdren said.

—Creating artificial “trees”—giant towers that suck  carbon dioxide  out of the air and store it.

The first approach would “try to produce a cooling effect to offset the heating effect of carbon dioxide and other  greenhouse gases,” Holdren said.

But he said there could be grave side effects. Studies suggest that might include eating away a large chunk of the ozone layer above the poles and causing the  Mediterranean  and the  Mideast  to be much drier.

And those are just the predicted problems. Scientists say they worry about side effects that they don’t anticipate.

While the idea could strike some people as too risky, the Obama administration could get unusual support on the idea from groups that have often denied the harm of global warming in the past.

OK.  Comparing Holdren to Dr. John I. Q. Niedelbaum Frink was a cheap shot.  Holdren clearly views such an intervention as a last ditch measure, to be used only in extremis.  But there is something more than a little mad-scientistish about this scheme, even under supposedly dire conditions.   In particular, it seems to embed a serious internal contradiction, related to the unanticipated side effects feared by “scientists” (just who, exactly, it would be nice to know.)  

The internal contradiction arises from the stated rationale for geoengineering, namely, that there are “tipping points” where positive feedback loops lead to extreme, discontinuous climate changes.  Such tipping points/discontinuities/positive feedback mechanisms are characteristic of chaotic systems.  These are complex systems with dense, unknown, and likely unknowable interconnections.  The response of such systems to shocks is highly sensitive to initial conditions, conditions which are impossible to identify let alone measure.  (Indeed, even if the relevant conditions could be identified exhaustively, and measured, even slight measurement errors could lead to wildly flawed predictions of response.)  

This is explained concisely in Useless Arithmetic: Why Environmental Scientists Can’t Predict the Future, by Orrin Pilkey and Linda Pilkey-Jarvis:

[p]erhaps the single most important reason that quantitative predictive mathematical models of natural processes don’t work and can’t work has to do with ordering complexity.   Interactions among the numerous components of a complex system occur in unpredictable and unexpected sequences.

So, geoengineering would represent an exchange of a devil we think we understand something about (runaway global warming in which climate changes discontinuously in response to a small incremental forcing) for a devil we don’t (the response of the climate to a big shock, e.g., man-made volcanoes, in the midst of an already chaotic event).  

The choice here does not seem to be obvious, although an advocate of the precautionary principle would argue that the very unpalatability of the choice dictates more robust action now.  But that’s a debate for another day.

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1 Comment »

  1. Maybe we could get The Greens to cryogenically freeze themselves to cool the planet and lessen man’s impact on the earth. They could be unfrozen once us unbelievers have the earth sufficiently cleaned up so as for them to live the quality lives that they deserve!

    Comment by Bob — May 5, 2009 @ 8:24 pm

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