Fran Pavley didn't come to the California Assembly in 2001 intending to put a Utah coal plant out of business or its workers out of jobs. She ran for office because she cared about the environment and thought she might find some way to break the logjam that kept lawmakers from regulating greenhouse gas emissions. During Pavley's first week in office, representatives from the Blue Water Network and the Coalition for Clean Air pitched an idea: For years, California had a waiver from the U.S. Environmental Protection Agency to set its own, stricter-than-federal standards for car exhaust. Why not pass a law to cut greenhouse gas emissions under the same authority?

Pavley, now a second-term state senator from the coast just north of Los Angeles, admits that she didn't quite understand the politics of it all. She succeeded nonetheless, and in 2002, then-Gov. Gray Davis signed Assembly Bill 1493, the "Clean Cars Standard," into law. The bill applied only to cars and trucks on California's roads; on its own, it could have little impact on global climate. Still, Pavley had established a beachhead: She had passed the country's first binding law to fight the pollution changing the climate.

In her next big move, Pavley went after the carbon footprint of energy production. More specifically, she went after coal. And this time, Pavley's legislating sent economic ripples far beyond her state's borders, to the communities of the rural Interior West that had over the past five decades come to depend on selling coal power to California's urban areas.

California has never had many coal plants; strict air-quality laws made them too expensive. Instead, starting in the 1960s, California utilities built thousands of miles of transmission lines to import electricity from Arizona, New Mexico, Utah and Nevada. When Pavley joined the Legislature, Southern California utilities imported close to half of their electricity from out-of-state coal plants, and exported the consequences – from respiratory illnesses to acid rain and mercury-polluted waterways. Environmentalists referred to it as "California's coal shadow." Toward the end of the 1980s, however, it had become increasingly clear that California couldn't completely escape that shadow: The coal burned for California's electricity emitted more carbon dioxide every year than 11 million cars. And carbon dioxide was warming the planet.

In 2002, the California Legislature ordered the state's utilities to begin adding renewables to their energy portfolios, 1 percent per year until they got to 20, with a deadline of 2017. Grid operators were urged to put efficiency and renewables before fossil-fueled electricity. But utilities, still reeling from the Enron-induced electricity crisis of 2000 and 2001, feared shortages and blackouts, and some were still planning more coal plants for neighboring states. Projects had been proposed in Nevada, Utah and New Mexico to serve San Diego and Los Angeles; the governors of California, Nevada, Utah and Wyoming were collaborating on the $3 billion Frontier transmission line to bring some wind, but even more coal-fired generation, to California. Had those plans succeeded, the carbon savings from Pavley's tailpipe law would have been wiped out completely.

Pavley and her allies weren't about to let that happen, and they had momentum on their side. In 2006, the Legislature easily passed a law moving the utilities' renewable energy mix deadline to 2010, and state Sen. Don Perata successfully carried a bill forbidding any new investment in power plants that emitted more than 1,100 pounds of carbon per megawatt hour – half what an average coal plant produces. Most sweeping of all, though, was Assembly Bill 32, the "Global Warming Solutions Act," which Pavley and Assemblyman Fabian Nuñez wrote in 2005 to push the state's total greenhouse gas load – including pollutants created on the state's behalf beyond its borders – down to 1990 levels before 2020. The bill needed 41 votes to pass. By the time Pavley and her fellow legislators were ready to subject it to a vote in 2006, it had 43 sponsors.

It would take several years for California's regulators, legislators and agencies to figure out how to achieve the global warming law's goal. But one step was clear: The state had to raise its renewable energy mandate steeply and quickly. The California Air Resources Board recommended 33 percent by 2020; then-Gov. Arnold Schwarzenegger made that official in 2008. It was a staggeringly ambitious target. "It's our Manhattan Project," Paul Douglas, the manager of renewable resource planning at the California Public Utilities Commission, said at the time. The generation associated with 33 percent is going to be the equivalent of 100,000 gigawatt hours." For perspective, in 2008 Pacific Gas & Electric sold to its customers 85,000 gigawatt hours of electricity. Close to half the state's renewable energy back then came from geothermal fields, and even that supplied less than 5 percent of the watts on the California grid.