What's amiss in emission calculations?

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 gives the impression that clearing the world’s forests, which absorb and diminish heat-trapping carbon dioxide, is good for the climate, the scientists note in the journal Science.

The problem boils down to this: In emission calculations, all fuel derived from plants and organic sources — including ethanol — is generally treated as if it has no effect on carbon dioxide in the atmosphere, even though biofuels emit carbon dioxide when burned. This might make sense if the source of the fuel were 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 burned. But if 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.

An energy and climate bill passed in June by the House of Representatives, the Kyoto Protocol, drafted in 1997, and the EU’s cap-and-trade law, in which companies trade emissions allowances, all 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 GHG, Searchinger said.  The article traces the problem to the 1990s, when international organisations worked to create a framework for emissions monitoring.

Problem cropped up in ‘97

In the mid-1990s, the IPCC recognised that when forests were cleared or when plants were harvested for bioenergy, the 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 IPCC chose to classify these emissions in the land-use category.

Searchinger said the problem arose in 1997, when nations hammered out the Kyoto Protocol, which was ratified by 184 countries. (The US 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 tailpipe emissions. The result is that the carbon release from bioenergy use is not counted at all.

The Science paper is one of several recent articles calling attention to the error. James A Edmonds, chief scientist at the Pacific Northwest National Laboratory, arrived at similar findings in a paper published in Science several months ago.

His study found that under current accounting methods, a commonly cited global target of limiting carbon dioxide to 450 parts per million in the atmosphere could result in a vast expansion of bioenergy crops, displacing nearly all of the world’s natural forests by 2065.

NYT News Service