By Paul Rogers, San Jose Mercury News

In the most sweeping action the federal government has taken to date to combat the warming of the planet, President Obama on Tuesday announced the nation’s first mandatory restrictions on greenhouse gas emissions from new and existing power plants.

The new rules, a centerpiece environmental initiative of Obama’s presidency, follow the lead that California set last year when it began to impose statewide greenhouse gas limits on power plants, factories and other industrial sources.

Speaking at Georgetown University, Obama took a swipe at climate deniers and described global warming as a major threat to the nation’s economy, farm production and its environment, noting that severe storms, droughts and forest

“We limit the amount of toxic chemicals like mercury and arsenic and sulfur in our air and water,” Obama said. “But power plants can still dump unlimited amounts of carbon pollution into our air for free. That’s not right. That’s not safe. And it needs to stop.”

The announcement sets up years of legal and political battles, with environmentalists and the administration on one side and the coal and utility industry, along with most Republicans in Congress, on the other. Opponents contend that the rules will cost too much and drag down the economy.

Experts said Tuesday that the president’s new climate strategy — which does not require approval from Congress — is expected to boost Silicon Valley companies involved in solar, wind, energy efficiency and other cleantech businesses, while also spurring more construction of large solar and wind projects in the Southern California desert.

“This is important for our environment and for the Silicon Valley companies that have made this the cleantech hub of the world,” said Carl Guardino, CEO of the Silicon Valley Leadership Group. “Companies like SunPower, SolarCity and Tesla Motors are leading the way in developing the innovative technologies and financing we need to meet the goals of deploying more renewable power, advancing energy efficiency and delivering on the promise of next-generation transportation.”

Obama’s new strategy on climate change also included broad new initiatives to increase renewable energy construction on federal land, tighten rules for appliance efficiency and begin planning for coastal cities and other areas to deal with the effects of the warming climate.

“This is exactly the way environmental policy moves forward in this country,” said Mary Nichols, who chairs the California Air Resources Board. “California starts out and takes a leadership post, then other states join in and the federal government comes in, and eventually we get a nationwide program. I think it’s great.”

Power plants — mostly from the burning of coal and natural gas to generate electricity — produce 33 percent of the nation’s greenhouse gases, the largest source. By comparison, all cars, trucks, planes, trains and boats account for 28 percent.

Obama is able to crack down on the dirtiest power plants through executive action.

In 2007, the U.S. Supreme Court ruled that the federal Environmental Protection Agency can regulate carbon dioxide, the primary gas that traps heat in Earth’s atmosphere, under the Clean Air Act — the same as it does with soot, lead and other types of air pollution.

“This is the change Americans have been waiting for on climate,” said Michael Brune, national executive director of the Sierra Club, based in San Francisco. “President Obama is finally putting action behind his words.”

Coal industry and utility groups are expected to try to block the rules through lawsuits. The new regulations, scheduled to be released next summer by the EPA, will make coal-fired power plants — which emit more greenhouse gases than other types of power plants — more expensive to build and operate.

“The last thing our economy needs right now is another layer of government red tape that will make it harder to grow businesses and hire more workers,” said House Speaker John Boehner, R-Ohio.

Obama’s new climate plan also directs the Interior Department to approve enough renewable energy projects, such as solar and wind, on public lands by 2020 to power 6 million homes. Millions of acres of California desert are federally owned by the Bureau of Land Management. In addition, it makes up to $8 billion in loan guarantees available for energy efficiency projects and advanced fossil fuel technology.

It also expands energy efficiency standards for federal buildings and home appliances, an area where California has led since the 1970s. And the plan commits to developing new gas-mileage standards for heavy-duty trucks on 2018 models and later.

Nichols said she doesn’t anticipate the new rules on power plants will upend California’s carbon-trading market or result in higher utility bills for California consumers. She noted the state already has a law requiring mandatory carbon limits from power plants and that California law requires that 33 percent of the state’s electricity come from renewable sources by 2020.

California uses very little coal-fired electricity because coal is not mined in the state and because power plants run on natural gas, which burns more cleanly, and have fit better with the state’s strict smog regulations. California’s electricity mostly comes from natural gas, hydroelectric power, nuclear energy and renewables.

Globally, the 10 hottest years on record have all occurred since 1998. Sea level rose 7 inches in the 20th century. Ice sheets in Greenland, Antarctica and the Arctic sea are all shrinking in size, as are most of the world’s glaciers.

“We don’t have time for a meeting of the Flat Earth Society,” Obama said. “Sticking your head in the sand might make you feel safer, but it is not going to protect you from the coming storm.”