A few years ago California became the first state to pass a law aimed at capping greenhouse gas emissions from major industries and threatening penalties for noncompliance. Opponents of California's 2006 Global Warming Solutions Act (AB 32) have been working throughout the year to defang the measure before it can take effect in January. The showdown between AB 32's supporters and its opposition comes to a head this Election Day, when Californians vote on Proposition 23, a ballot measure written to keep the state from implementing AB 32's provisions until the state unemployment rate stays at 5.5 percent or below for four consecutive quarters.

Prop 23 supporters contend that cutting carbon dioxide and other greenhouse gas emissions 25 percent by 2020 places a heavy financial burden on the state's existing industries that will lead to lower profits, discourage some businesses from moving to California and eventually create massive layoffs.

Those opposed to Prop 23 believe that the state's businesses should take the environmentally responsible action of adhering to AB 32's provisions, and that any job losses in the short term will be more than compensated for by employment opportunities in the state's growing renewable energy industry. They also point out that any attempt to meet the ballot measure's employment requirements is a fool's errand—California's unemployment rate in September stood at 12.4 percent.

The Prop 23 campaign has suffered from its own disingenuousness and appears to be losing traction. Earlier this year it was revealed that most of its biggest supporters, and donors, hailed from out-of-state oil companies—in particular Valero Energy Corp. and Tesoro Corp., both based in Texas. In fact, the millions of dollars these companies put into Prop 23 helped get it on the November 2 ballot. As a result, last week 68 investors that collectively manage $415 billion  in assets issued a statement urging voters to reject Proposition 23 (pdf).

Scientific American asked Stanford University professor of civil and environmental engineering Mark Jacobson to weigh in on the debate and the possibility that, if Prop 23 fails, the sentiments behind the ballot measure might resurface elsewhere.

[An edited transcript of the interview follows.]

Is Prop 23 still a major issue in the upcoming election? What is at stake if it does pass?
It looks like Prop 23 is headed for defeat according to the latest polls. If it were to pass, it would be devastating for efforts to address CO2 as a greenhouse gas, since California right now is the only state that can control CO2, thanks to a waiver from the EPA [U.S. Environmental Protection Agency] allowing the state to do so. Even though the U.S. Chamber of Commerce is suing the EPA to try to prevent implementation of California's waiver, other states can now follow California's lead and obtain such a waiver. If Prop 23 passes, however, it is unlikely that other states will implement CO2 controls, since they would feel they do not have a mandate to do so. In sum, Prop 23 would dissuade other states from implementing CO2 controls and prevent California from implementing its own controls, damaging the green tech industry.

Why did Prop 23 (at least at one point) become such a large issue related to this election? Are Californians concerned that AB 32 will cost them a lot of money, in taxes or otherwise?
Proponents of Prop 23 have provided inaccurate information about the effects of air pollution regulation. The financial benefit of air pollution regulation, compared to the cost of such regulation, historically (from 1990 to present) has been four to one, according to the EPA. The White House Office of Management and Budget (OMB) came up with a similar conclusion (and ratio) under the Bush administration.

[In 2003 the OMB reported that "societal benefits" of EPA regulations significantly outweighed costs of compliance between the years of 1992 and 2002. After analyzing the costs and benefits of 107 regulations promulgated by agencies across the federal government, OMB found that total benefits of federal rules were three to five times greater than total costs. Benefits were estimated at $146 billion to $230 billion annually, whereas yearly costs were estimated at $36 billion to $42 billion.]

Why would a California citizen want to vote for Prop 23? What does a voter have to gain by its adoption?
Voters would have been deceived into thinking that Prop 23 will cost jobs. There is little to gain.

If Prop 23 is not adopted, where else might the sentiments behind it resurface? Might Proposition 26 also be an outlet for those opposed to spending the money to cut greenhouse emissions?
Yes, Prop 26 is a related ballot initiative designed to allow industry and others to continue polluting. So long as the oil, coal, gas, biofuels and other combustion industries have money they will continue to spend it in efforts that result in keeping the air unhealthy and climate problems alive with the goal of making more money for themselves.