Seven Thousandths of a Degree

May 20th, 2009

Keith Hennessey, using the NHTSA’s analysis to see what effect Obama’s proposed emissions and fuel efficiency standards will have:

  • Both options would reduce the global mean surface temperature by one-thousandth of one degree Celsius by 2030.  The Obama option would reduce the global temperature by seven thousandths of a degree Celsius by the end of this century.
  • The effects on sea level are too small to measure by 2030.  By 2100, the Obama proposal (technically, the TC=TB proxy) would reduce the sea-level rise by six hundredths of a centimeter.  That’s 0.6 millimeters.

Hennessey served during the Bush administration and coordinated Bush’s fuel efficiency standards. It is worth reading his entire entry; it is an apolitical look at Obama’s proposal.

This underscores just how difficult having a significant effect on global warming would be. Obama’s proposal is quite aggressive — Hennessey calculates it will require about a 5.8 percent increase in fuel efficiency per year through 2016 — but its short and long term effects on the environment are not significant. Costs borne by consumers, and job losses (the NHTSA estimates around 150,000 jobs lost in the auto industry, resulting from more expensive cars and thus less cars sold) are rather significant.

So the economic effects of this policy are significant, but the environmental effects are not; imagine what it would take to seriously retard global warming. It makes clear the trade off in doing anything of note to slow global warming: significant economic loss, and therefore suffering for people across the globe.

This does not mean that this policy should not be implemented — but it does mean justifying it on its environmental effect does not seem reasonable. Reducing the United States’ dependence on oil is certainly a proper goal.

(Via Alex Tabarrok.)