I caught a clip of Sen. Obama bemoaning the image of the U.S. in the world, faulting us for using a quarter of the world’s energy, while being only 3 percent of the world’s population.

I was under the impression that our population of 300-million-plus was more on the order of 5 percent of the world population of 6-billion-plus. In fact, the greens whose talking points Obama was otherwise parroting say so over and again — keening about the injustice of such a privileged few emitting a quarter of the world’s greenhouse gases.

Except of course, that figure is actually between 22 and 23 percent of the world’s GHGs, last time I checked — for my forthcoming book. It is easy to imagine that — with Asia growing fast, and our own emissions dropping the past two years — the greens’ figure is now even further from the truth.*

Does Sen. Obama have a problem with a mere 3 percent — 5 percent, whatever — of the world’s population paying nearly a quarter of the U.N.’s expenses? Let’s assume “No.” So, why not? Presumably this is OK not from a pure redistributionist perspective, but because we create a quarter of the world’s wealth. Ah. I think we’re onto something about those energy use complaints!

In fact, the greens insist in the context of economic comparisons on using the Market Exchange Rate as their metric (although David Henderson has made clear it is utterly inappropriate; Purchasing Power Parity is the preferable standard). Apply MER to our equation here, and you see that the U.S. produces 28 percent of the world’s wealth in return for its 22 percent or so of the world’s GHGs.

Heavens. As it happens, the U.S. is disproportionately GHG efficient. If only the rest of the world met our standard, Kyoto would be met several times over.

But of course, bringing the U.S. to heel on Kyoto is not about GHG emissions, per se. It’s about wealth transfer, “leveling the playing” field, and all the rest that our friends have admitted to.

Turns out, Obama’s sloppy math has opened up an issue that’s a real debate-changer — if there were a debate, that is. One of the other candidates could score some points against him on this. But I doubt it.

*UPDATE: In fact, Obama’s claim is now further from the truth. The IPCC 4th Assessment Report estimates that global greenhouse gas emissions in 2004 were 49 GtCO2 eq. Total (gross) U.S. GHG emissions in 2004 were 7.078 GtCO2 eq. That means U.S. GHG emissions account for only about 15 percent of the global total. The difference between 15 percent and one-quarter of global GHGs is about equal to the emissions from the EU-15 — not an inconsequential amount.