You may not be able to trust Exxon for objective data on emissions and our planet but you sure can't trust advocacy-based political groups in a highly-charged political state like California either.
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... 
writes the San Francisco Chronicle.

Clearly the California Air Resources Board had a goal in mind - endorsing a solution by trumping up data to make it the clear choice - and that meant boosting pollution estimates by 340%.

Result: Costly upgrades to heavy-duty, diesel-fueled off-road vehicles used in construction and other industries, money that never needed to be spent but for which businesses have no choice, and in a recession could certainly be spent better than an unfair mandate, and therefore a forced subsidy, for diesel manufacturers.

Previously, this ridiculous advocacy group overstated 'deaths' related to diesel emissions for the same purpose, which means now the state has to spend money undoing all of their work.

The difference between the far left and the far right when it comes to manufacturing results to meet their agendas is non-existent.
Mary Nichols, chairwoman of the California Air Resources Board, offered no explanation when The Chronicle questioned her about the diesel emissions miscalculation. She was recently asked why the air board estimate of a nitrous oxide source was off by at least a factor of two - air board scientists have since revised their numbers, and data show the estimate was off by 340 percent. Nichols' response: "I can't answer that for you."
Maybe voters can answer it in November.