The figure below shows the relationship of carbon dioxide emissions from the burning of fossil fuels (with data from the U.S. Energy Information Agency) with global GDP (as measured in PPP terms and reported by Maddison).

A few things stand out.

First, the relationship between economic activity and carbon dioxide emissions is exceedingly close.

Second, from 2001 to 2006 the rate of increase of emissions per dollar of economic activity doubled as compared to the period 1990 to 2000. This is the same change in emissions that we documented in Nature last spring (PDF).

Third, while it is uncertain what exact effect the global economic slowdown will have on emissions, a good bet is that emissions will increase at a rate proportionately less. Though there is some uncertainty due to the fact that the sowdown may manifest itself to a greater extent in less carbon intensive sectors of the economy, such as in banking.

Finally, in 2006 the world averaged 0.62 tonnes of carbon dioxide for each thousand dollars of economic activity. To achieve goals of decarbonization of the global economy will require that this figure be reduced to between 0.15 to 0.25 tonnes per thousand dollars by 2030 (depending on your target and assuming a 3.5% annual GDP at PPP growth rate). No developed country in the world is anywhere close to achieving this level of decarbonization and no country is remotely on a path to meet such a goal.