When an environmental law or regulation passes in California, it usually comes as a surprise to no one. After all, it’s California. So when the California Air Resources Board unanimously approved regulations to reduce diesel emissions—despite opposition from the trucking industry—most thought of it as “California being California.”

Now California may significantly reduce the regulations, because scientists drastically exaggerated the diesel emission levels from off-road machinery. The San Francisco Chronicle reports:

The pollution estimate in question was too high—by 340 percent, according to the California Air Resources Board, the state agency charged with researching and adopting air quality standards. The estimate was a key part in the creation of a regulation adopted by the Air Resources Board in 2007, a rule that forces businesses to cut diesel emissions by replacing or making costly upgrades to heavy-duty, diesel-fueled off-road vehicles used in construction and other industries.

The staff of the powerful and widely respected Air Resources Board said the overestimate is largely due to the board calculating emissions before the economy slumped, which halted the use of many of the 150,000 diesel-exhaust-spewing vehicles in California. Independent researchers, however, found huge overestimates in the air board’s work on diesel emissions and attributed the flawed work to a faulty method of calculation—not the economic downturn.

This isn’t the first time diesel regulations in California have come into questions because of faulty scientific reporting. In December 2009, two of the eleven board members “asked that the anti-pollution rules be suspended because they were partially based on a report by Hien Tran that found particulates in diesel emissions account for 3,500 premature deaths a year in California. Tran falsely claimed he had a doctorate in statistics from UC Davis.”

The cost of such regulations, which air regulators peg at $5.5 billion for the trucking industry, will increase the cost of transporting goods for businesses. Richard Lee of Tim A. Manley Trucking said, “It makes no sense to saddle the trucking industry with regulations that absolutely assures the collapse of thousands of taxpaying businesses.” For those businesses that don’t collapse, they’ll simply pass those costs onto the consumer. California is right to pull back on stringent, costly regulations on diesel emissions. Faulty science seems to be a running theme for justifying environmental regulations, and that, on top of the massive economic costs, is why the Air Resources Board should reconsider its Global Warming Solutions Act of 2006 (AB32), which would seek to reduce carbon dioxide levels to 1990 levels by 2020.

Contrary to the claims that AB32 will boost California’s economy from green investment and green job creation, the state cap-and-trade program would do the complete opposite by increasing energy prices, thereby causing a considerable reduction in economic growth, household incomes, and employment. Whether it’s federal or state, the logic is the same: Higher energy taxes will destroy many more jobs than they create.