No one likes to be left out. (Photo by charamelody.)

Last week, I highlighted some energy projections from 2000 or so that substantially underestimated the growth of renewables. Mainly I wanted an excuse to repost Michael Noble’s list. So as not to merely thieve, I added a few musings of my own, reflecting my ongoing obsessions with the dynamics of distributed energy and the values-based assumptions buried in economic models. I didn’t think about it all that much, to be honest, nor did I aspire to offer a comprehensive account of why projections fail. (The much-more-qualified Nate Silver has a book on that subject coming out in September.)

Turns out, though, the post was quite popular! It has now been linked to by both David Leonhardt and Paul Krugman of The New York Times. Normally I’d be thrilled, but the post in question has the unfortunate feature of being, um, wrong. Well, maybe not wrong, but it nibbles around the edges and misses the main course.

Why were projections of renewable energy growth from 2000 so woefully off the mark? The main answer, which I passed over in my post, is policy.

The International Energy Agency and U.S. Energy Information Administration do not try to predict policy changes; they project based on the current policy regime. In 2000, there wasn’t much in the way of clean-energy policy. Since then, however, there’s been a great deal, and those policy changes are the biggest driver of renewable energy growth. Michael Levi makes the point well: “without supportive policy that wasn’t in place a decade ago, renewables wouldn’t have done nearly as well. If we want more renewable energy in the coming years than the EIA and IEA currently project, we’re going to need new and more robust policies too.”