‘Verifying
 Emission Cuts’

Cheryl Hogue’s article about the Copenhagen Accord mentioned the possibility of verifying emissions cuts through atmospheric measurements but understated the difficulty associated with deriving emissions increases or decreases from these measurements (C&EN, March 8, page 34).

The article said that there are models to estimate impacts from releases (the one for accidental releases mentioned in the article is considerably less well-known and less frequently used than the multitude of models that have been developed for continuous sources of air pollution) and that there are also models to infer the locations of a relatively small number of sources of relatively unusual emissions (from nuclear fuel processing). But this is very different from using ambient measurements to quantitatively derive regional changes in total emissions that are emitted almost everywhere by everything (with different stack temperatures, dispersion characteristics, etc.).

Those who are interested should 
look at the research that has been done over the past several decades with EPA’s six criteria air pollutants and the use of ambient measurements. Whereas atmospheric measurements (taken from carefully chosen locations) would be an important qualitative check, as acknowledged at the end of the article, it is considerably more difficult for the models to accurately “determine the location and magnitude of the original emissions,” as stated in the middle of the article, particularly when you are talking about “the location” being an entire country.

Todd Tamura
Petaluma, Calif.