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.
Comparison to 2000: Land-Use Change
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:
- In the revised data, total CO2 emissions from land-use change increased between 2000 and 2005. It is only the share of emissions attributed to land-use change that decreased. This result reflects that fact that while emissions in the land-use change increased, emissions in other sectors increased at even faster rates.
- The apparent decrease in land-use change emissions compared to the 2000 chart is entirely due to revised methodologies used to calculate deforestation in the underlying FRA data, and not to any actual decrease in deforestation rates. The working paper discusses this in more detail.
- Estimates of CO2 from land use change are still subject to large uncertainties. Studies cited by the IPCC 4th Assessment Report show error ranges of up to ±2,933 MtCO2 (±0.8 GtC) at the global level in the 1990s.
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.