In recent years, as developed economies have seen downturns in their economic growth due to the global financial crisis, an inevitable consequence has been a corresponding decrease in carbon dioxide emissions. It would be tempting to conclude that based on the decrease in emissions, the 2020 UK Climate Change Act target is now easier to reach. However the lesson that should be drawn is the folly of relying solely on carbon dioxide emissions as a policy metric, since emissions are so tightly coupled to economic growth.
The metric that we should be paying attention to is the rate of decarbonization of the economy, measured in carbon dioxide emissions per unit of GDP, as this integrates two metrics that we want to see go in different directions -- GDP up and emissions down. When we look at the decarbonization of the UK economy, we see that while the UK economy has continued to decarbonize in recent years -- significantly so in 2009 -- the overall challenge of decarbonizing the UK economy has changed very little.
I illustrate this with the following graph which provides an update to Figure 2 in my 2009 paper on the UK Climate Change Act.
The four red dots connected with the red line show actual decarbonization of the UK economy from 2006 to 2009. This data is encouraging as it shows a significant rate of decarbonization during the economic crisis. It is not directly comparable to the dim lines underneath since GDP growth (contraction) fell outside the bounds of my 2009 analysis. The dashed black line shows the rate of decarbonization implied by a 2.0% GDP growth 2010 to 2022, based on the updated data. There is some reason to believe that 2010 actually saw a recarbonization of the UK economy, which would imply that the next red dot would be higher than the one for 2009 -- we shall see when official data is released.
Regardless what happened in 2010, the implication of the updated graph is virtually identical to the conclusions that I reached in the 2009 paper and in The Climate Fix: To be on target to meet its 2020 emissions reduction target the UK needs to become as carbon efficient as France by no later than 2015, under any positive future GDP growth. The reduction in emissions in 2009 do not alter that conclusion. The overall sense I get from media reports is that this reality is generally, if not universally, understood.
Now for something interesting that I cannot explain [UPDATE: See the comments for a valuable exchange with the ever-helpful Harrywr2.]. I routinely use the US EIA data on carbon dioxide emissions, because it is authoritative and they use an apples-to-apples approach for all countries around the world, enabling comparative and aggregated analysis. But when comparing the US EIA data with the official data from the UK (here in PDF) there is a distinct bias -- the UK has its emissions growing at a considerably slower rate than does EIA, as shown in the following figure.
