From Bloomberg News:

By Lynn Doan

Governor Jerry Brown said it may take as long as 18 months for California, the third-largest oil-producing state, to complete an environmental review of the oil and gas drilling technique known as hydraulic fracturing.

Technological advancements have ignited a boom in the development of fields that were once deemed uneconomical, particularly in shale formations. California lawmakers approved regulations for state oversight of fracking in September.

The state’s Monterey Shale field may hold 15.4 billion barrels — two-thirds of the nation’s shale-oil reserves, according to U.S. estimates. Environmental groups including the Center for Biological Diversity’s Climate Law Institute say fracking poses unacceptable risks of air and water pollution.

“I think we ought to give science a chance before deciding on a ban on fracking,” Brown, a 75-year-old Democrat, told reporters following a conference in San Francisco yesterday.California’s study will become “the most comprehensive environmental analysis of fracking to date,” he said.

The technique forces water, sand and chemicals underground to break up rock layers and free trapped oil and gas. It has helped drive U.S. oil output to the highest level since 1989.

While groups have raised concerns about pollution from fracking, Brown said the drilling boom has also helped cut U.S. emissions as companies switch from burning coal to cheaper and less-carbon-intensive gas.

“So this is a very complicated equation,” he said. “You can be sure that California is doing everything it can to reduce greenhouse gases and support a sustainable economy.”

Brown spoke after a ceremony with the governors of Oregon and Washington to sign an agreement to put a price on emissions and adopt fuel standards, bringing their efforts to cut greenhouse-gas pollution closer to those of California and British Columbia.

Under the agreement, Oregon will build on existing programs to set a price for carbon emissionsand Washington will impose limits and establish a market to meet those caps. British Columbia and California will maintain existing efforts, and all four will link programs “where possible” to offer consistency.

The accord falls short of creating a regional carbon market, an aspiration in California since the state began a cap-and-trade program when the U.S. federal government was unable to come up with a national system in 2010. A movement to establish a market across the western U.S. and parts of Canada fell apart two years ago after some states decided to pursue other means of cutting emissions.