SACRAMENTO -- Gov. Jerry Brown on Monday called California "the epicenter of climate change," and he urged other states to work with him to halt the rising temperatures that threaten the planet's future.

Brown's comments came during a speech to a University of California agricultural economics group. The address follows recent reports from scientists who warn that hotter temperatures are causing more intense wildfires and that it's already too late to stop the collapse of a huge West Antarctic ice sheet that will swell sea levels by as much as 12 feet.

The severe drought responsible for turning some of the Central Valley's prime farmland into crusty dirt is one example of how climate change is already impacting the Golden State, Brown said.

"I have a ranch where the temperature was over 100 degrees for 35 days," Brown said. "I know what heat looks like. Rattlesnakes like it, and it's not easy to manage if someone throws their cigarette butt out the window."

Brown sees his high speed rail project as one way to reduce greenhouse gas emissions and get some drivers off California's roadways. Each year, vehicles here travel 332 billion miles, and that figure is set to rise by 25 billion miles by 2020, Brown said.

For decades, Brown has garnered praise from environmental groups for making California a leader in energy-efficient building and appliance standards, and for signing a law requiring that 33 percent of the state's electricity come from renewable sources like solar and wind by 2020.

Over the past year, he has come under increasing criticism by green groups for his support of hydraulic fracturing -- or fracking -- the practice in which oil companies inject water and chemicals into the ground to crack rock formations to release oil and gas.

About two dozen people from a group called Californians Against Fracking demonstrated outside the California Museum, in Sacramento, where Brown gave his speech. They also disrupted a speech Brown gave earlier this year in Los Angeles on climate change.

For Hillary Aidun, one of the protesters, the reason to demonstrate is simple. "Climate leaders don't frack," said Aidun, who is affiliated with the Center for Biological Diversity.

Last year, Brown rejected plans for a statewide moratorium on fracking similar to New York's. Instead, he signed a law in September that requires companies that conduct fracking operations to notify all nearby property owners, obtain a permit from the state, conduct groundwater testing and disclose the chemicals they are using. The law takes full effect in 2015.

Environmentalists are launching local efforts to ban fracking, which they say increases the risk of groundwater pollution and boosts greenhouse gas emissions. On Tuesday, Santa Cruz County supervisors are expected to vote to ban the practice entirely in unincorporated Santa Cruz County. Measures to ban it are heading for the November ballot in San Benito and Butte counties.

"We are not going to shut down a third of our oil production and force more oil coming from North Dakota, where they are fracking a lot more, to come by train or more boats and ships coming in from all over the world," Brown said on CNN on Sunday. "We have got to start hammering at the demand as well as the sources of fossil fuel."

Contact Jessica Calefati at jcalefati@bayareanewsgroup.com and at 916-441-2101. Follow her at Twitter.com/calefati. Contact Paul Rogers at progers@mercurynews.com. Follow him at Twitter.com/PaulRogersSJMN.