Overestimate fueled state’s landmark diesel law
10/08/10 San Francisco Chronicle — California grossly miscalculated pollution levels in a scientific analysis used to toughen the state's clean-air standards, and scientists have spent the past several months revising data and planning a significant weakening of the landmark regulation. The problem, and the revised counting method, came to light after Robert Harley, a UC Berkeley professor of environmental engineering, and a colleague at Lawrence Berkeley National Laboratory did their own evaluation, which was published in December in the journal Atmospheric Environment. Harley found that the board's estimates of nitrous oxide were too high by a factor of 4.5 and its estimate of particulate matter was off by a factor of 3.1, an extraordinarily high amount to be off scientifically. "The difference is large enough that it changes policy," Harley said.