There’s a big carbon footprint report out today from Brookings. It ranks cities according to their per capita carbon emissions. Sort of, anyway.

Before I pick on it a little, I guess I should mention that Northwest cities do exceptionally well. Out of the 100 cities in the analysis Portland ranks 3rd, Boise is 5th, and Seattle 6th. There’s very little difference between them.

That’s wonderful and all, but the analysis only covers about 50 percent of emissions. It excludes, for instance, commercial and industrial energy, maritime and aviation emissions, and some other signficant pieces of the pie.

The scope of the research is understandably limited to available and comparable data, which makes the rankings possible. Specifically, that means the numbers for residential energy and transportation. And that’s a winning hand for Northwest cities simply because the region’s electricy grid is based heavily on hydroelectricity (and hydro doesn’t emit greenhouse gases). Now, there’s nothing wrong with taking credit—our electricity system is pretty darn clean—but in an analysis of such narrow scope, it tends to make us look better than we really are.

What’s surprising to me is how well the Northwest cities also do in terms of transportation emissions. Portland ranks 10th, Boise 11th, and Seattle 27th. Frankly, I’m surprised both by the rankings and the differences between them; surprised enough that I’m a little skeptical. But what do I know?

Maybe the most important lesson from the report is a semi-geeky one.

  • Greenhouse gas inventories are an emerging field—and they’re tough. There are few standardized accounting protocols, the measurements are damnably complex, and any accounting requires a bunch of judgment calls. (We’ve written about this a bit here.) It turns out that one of the most important climate strategies for local governments is simply figuring out what their emissions are. Toward that end, Seattle and King County should take credit—they’re pioneering this stuff.

    I don’t want to sandbag the report. I’m glad Brookings did it. It’s a good exercise, even if it’s only a partial accounting. Plus, they should also get props for framing the issue just right: cities matter, but we really need comprehensive federal legislation. In fact, the Seattle P-I has an exceptionally good article that contextualizes the study:

    Another problem with these assessments, according to a local energy policy expert not involved in the project, is that nobody really agrees on how to measure a carbon footprint.

    “There is no one perfect method for these calculations,” said Anne Steinemann, a University of Washington professor of civil and environmental engineering. Steinemann and colleagues at Vanderbilt University recently analyzed carbon footprint methods and found them highly inconsistent.

    “There isn’t a standard, and it’s maddening,” agreed King County Executive Ron Sims, who is leading an effort to create such a standard. Last week, Sims was at a meeting in Albuquerque, N.M., sponsored by a U.N. initiative called the International Council for Local Environmental Initiatives, where officials discussed the lack of a routine measure.

    “We’ve been working on that for King County and expect to come out with something very detailed and comprehensive sometime this summer,” Sims said. Numerous municipalities have contacted King County eager to adopt this much-needed urban planning yardstick, Sims said.

    Steinemann said she had not read the Brookings Institution report but respects Brown’s expertise in this area and assumes that the data had to be limited in order to maintain the consistency of their analysis.

    “It can be useful when taken in context,” she said.

    That’s exactly right: useful when taken in context.

    I applaud the nuance from everyone—from reporter Tom Paulson, from the author Marilyn Brown, and, it seems, from everyone quoted about the effort. It’s nice to see an elevated discussion like this.