Geoengineering: A Reasonable Solution to Climate Change?

Posted by Don Fullerton on Nov 13, 2009

Filed Under (Environmental Policy)

In SuperFreakonomics, the new book by Steven Levitt and Steven Dubner, the authors suggest geoengineering as a possible solution to climate change.  Their assertion has been so controversial that they devoted a long blog entry to its defense.  What is geoengineering, and how should economists think about it?

The National Academy of Sciences defines geoengineering as “options that would involve large-scale engineering of our environment in order to combat or counteract the effects of changes in atmospheric chemistry.”  The specific geoengineering that Levitt and Dubner analyze calls for injecting sulfate aerosols into the stratosphere.  The idea is that the aerosols form a shield to reflect sunlight, thus lowering global temperature.  A similar cooling effect occurs naturally after large volcanic eruptions.  Paul Crutzen, the Nobel Prize winning chemist, estimates that $25-50 billion could be enough to construct a sulfate aerosol shield to counteract a doubling in the current atmospheric concentration of greenhouse gases (see “Albedo Enhancement by Stratospheric Sulfur Injections: A Contribution to Resolve a Policy Dilemma”, Climate Change 77: 211-200).

The traditional solution to climate change calls for limiting greenhouse gas (GHG) emissions that cause global warming.  In a “meta-analysis” discussed in the Stern Review (p.242),  a 50% reduction in worldwide greenhouse gas emissions could cost 2% of world GDP or more.  Let’s see,  world GDP is about $70 trillion, so a 2% reduction in GDP costs $1.4 trillion.   While the comparison here is not exactly apples-to-apples, the point is that these mitigation cost estimates are significantly higher than geoengineering cost estimates ($25-50 billion).  Thus, it superficially appears that geoengineering is the “correct” economic solution to climate change.

However, geoengineering is an ex post solution, where society waits for the symptoms of climate change to become so severe that geoengineering is the only remedy to treat the symptoms.  In contrast, GHG mitigation tries to prevent the symptoms from ever occurring by trying to correct the root cause.

Many present the geoengineering solution as an insurance policy against the disaster of runaway climate change.   Shall we rely on the theory that temperatures can be reduced later, while we continue unlimited burning of carbon?  What if that insurance doesn’t work.  What if geoengineering doesn’t cool the planet as theorized?  What if the sulfates cause other environmental problems?  In addition, geoengineering cannot necessarily counteract the economic effects of severe climate change.  Imagine that society waits for “proof” of climate change, such as waiting for large sections of Arctic ice sheets to break off and raise sea level by a few feet.  At that point the economic damage is irreversible – regardless of the geoengineering temperature correction – with millions of people displaced from low-lying areas, billions (if not trillions) of physical capital submerged, and severe disruption to economic activity.  Then would GHG mitigation look like the bargain solution?