Over the past few weeks I’ve been engaged in an email conversation with about 30 energy analysts and environmental reporters about the rebound effect. That conversation has had many threads, but one of particular interest is a specific example I asked the rebound advocates to create. After some resistance to the idea, someone from the Breakthrough institute took up the challenge, but has thus far failed to respond to technical critiques of his example that reduce the projected rebound effects by an order of magnitude or more.
I summarized where we stand in a memo that I sent to the group today, which is downloadable here. The key points from my memo are:
1) In an effort to avoid misunderstandings about the complex phenomenon of rebound, I proposed to an email list of about 30 analysts and energy/environmental reporters that those supporting large rebound effects produce a simplified example, so we could dig into the buried assumptions that always afflict such analyses.
2) Jesse Jenkins of the Breakthrough Institute offered such an example, but failed to respond to substantive critiques of the assumptions behind that model that reduced the calculated rebound effect by factors of roughly 10 to 20.
3) Nevertheless, there was general agreement that the relevant research question should be “under what conditions is rebound a problem, and in those cases, how big is it?” Once this question is accepted, however, making blanket categorical statements like “energy efficiency never saves energy” (as blog posts on the Breakthrough Institute’s web site routinely do) is no longer appropriate.
4) The normal burden of proof is on those advocating the existence of some unexpected and novel effect to show the underlying causal mechanisms that lead to that result, so the assumptions can be peer reviewed. I can’t prove that large rebounds don’t exist, just like I can’t prove that black swans don’t exist in the absence of a perfectly accurate universal census of swan colors, but if someone brings me a black swan, the problem is solved. And that’s what those of us skeptical about large rebound effects continue to request: bring us a black swan!
I’m still waiting for a substantive technical response from the advocates for large rebounds, and will post more when I hear back.