A little over two years ago I wrote an article for Environmental Leader declaring that 2007 would be the year of "Peak Carbon" in the US, such that GHG emissions would generally decline from that point on (with accommodation for random short blips upwards). In the short term I figured that the economy would get the curve to peak, and that then a series of other policy and economic factors would continue to drive the emissions downward in a steady matter.
If you read the comments you'll see that some people thought the whole notion was stupid, some said "doesn't matter unless China reaches peak carbon also", and others disagreed emissions were going to peak. I didn't disagree with the China point, but felt (and still feel) like a true downward trend in US emissions is an important milestone.
Based on the latest numbers from the EPA, it looks like there is good news on two fronts (see chart from EPA's carbon website). First, the data so far supports my theory - 2008 was lower than 2007, and 2009 took another good step downward. But even if you don't care about my prediction, the other good news was that the 2009 drop was bigger than the economic downturn would suggest. This indicates some real decarbonization of the economy, which is encouraging.
Like my predication, the data suggests that the decarbonization wasn't from a single trend, but from the accumulation of multiple shifts. Interestingly it was split between a reduction in the energy intensity of the economy, and a decarbonization of the energy supply itself. While the first is a mixed blessing since it usually indicates a further erosion of the US industrial base (and if those jobs just moved somewhere else, then the emissions just moved with them), but the second is a good sign, especially given the lack of momentum in federal energy and GHG emissions policy.
One thing that I think we need to start looking at more closely is the effectiveness of local, state and regional level efforts at clean energy deployment, coupled with new roadblocks to new coal plants. Evidence would suggest that there are some successes there that we should be paying attention to, and trying to replicate more broadly.
I also continue to believe that the 2009 experience will be representative of the general nature of the decarbonization of the US - the cumulative effect of lots of small and medium sized actions and policies, as opposed to a single big policy or technology which has a dominant effect.
So overall I'm gaining even more confidence in my prediction, and continue to hope that I was right on the money! If you want to vote for or against me, I've registered this as bet #436 at longbets.com. So far there's 7 against and 0 for!