The original version of this chart appeared in Navigating the Numbers: Greenhouse Gas Data and International Climate Policy. The original chart used year 2000 data; the data used in this chart are from 2005.
The most significant change compared to 2000 concerns the net contribution of atmospheric CO2 from land-use change. In both 2005 and 2000, these data come from research published by Woods Hole Research Center, which was revised in 2008. Revised rates of deforestation in the underlying Forest Resources Assessment (FRA) data produced significantly lower estimates of CO2 from land use change compared to the previous research. As a result, CO2 from land use change accounts for a significantly lower share of GHGs than in the original chart: 12.2% as compared to 18.2%.
It is important to note that:
Update: In November 2009, a group of forest experts (which included WRI) released this statement on how new research was producing revised, lower estimates of emissions from land-use change. That statement put the best current estimate at about “15 percent if peat degradation is included,” cautioning that a precise estimate is impossible due to substantial uncertainties. The joint statement is consistent with the 12.2% estimate in this chart, since the latter does not include peat degradation.