Sliding Yardstick for Emissions Is Problematic
By SINDYA N. BHANOO
Published: October 23, 2009
An accounting problem in the way some greenhouse gas emissions are calculated could critically hobble efforts to reduce them in coming years as nations move to combat global warming, scientists warn in a new report.
The accounting irregularity even gives the impression that clearing the world's forests, which absorb and thereby diminish heat-trapping carbon dioxide, is good for the climate, the scientists write in an article published Friday in the journal Science.
The problem boils down to this: In emission calculations, all fuel derived from plants and other organic sources -- including ethanol -- is generally treated as if it has no effect on carbon dioxide in the atmosphere, even though biofuels do emit carbon dioxide when burned.
This might make sense if the source of the fuel were, say, a crop of corn grown on barren land specifically for use as fuel, because the crop would have absorbed carbon dioxide as it grew, offsetting what it emits when ultimately burned.
But if an existing stand of forest land is cleared for fuel, its ability to absorb carbon dioxide is lost, and the net balance of the gas in the atmosphere goes up.
Several measures -- including an energy and climate bill passed in June by the House of Representatives, the Kyoto Protocol, drafted in 1997, and the European Union's cap-and-trade law, in which companies trade emissions allowances -- exempt emissions from biofuels without taking the source of the fuel into account, said Timothy D. Searchinger, the study's lead author and a research fellow at Princeton University.
''It literally means you can chip up the world's forests and burn them'' for fuel without noting the effect on the world's greenhouse gases, Mr. Searchinger said.
The article traces the problem back to the 1990s, when international organizations worked to create a framework for emissions monitoring. In the mid-1990s the Intergovernmental Panel on Climate Change recognized that when forests were cleared or when plants were harvested for bioenergy, the resulting release of carbon dioxide should be counted either as land-use emissions or energy emissions, but not both.
To create an international standard and avoid double-counting, the panel chose to classify these emissions in the land-use category.
Mr. Searchinger said the problem arose in 1997, when nations hammered out the Kyoto Protocol, which was eventually ratified by 184 countries. (The United States refused to ratify the agreement.)
The protocol imposes no limits on land-use emissions in developing countries. So if a forest is cleared in Indonesia and ends up as biofuel in Europe, Asia does not count the land-use emissions and Europe does not report the tailpipe emissions.
The end result is that the carbon release from bioenergy use is not counted at all.