The Clean Air Act is the president's handiest tool for moving forward. The Natural Resources Defense Council has outlined an approach, using that law, which it figures could cut the emissions from existing power plants by 26 percent from their peak in 2005.
The World Resources Institute has recommended several other actions, all within the president's unilateral powers: phasing out the use of certain hydrofluorocarbons; setting lower standards for the methane emissions from natural gas systems; and focusing on more energy efficiency from homes, businesses and factories.
Obama set a new energy efficiency goal in his speech, but offered few specifics. "Let's cut in half the energy wasted by our homes and businesses over the next 20 years," he said. "We'll work with the states to do it. The states with the best ideas to create jobs and lower energy bills by constructing more efficient buildings will receive federal support to help make it happen."
Some executive actions should be easy to accomplish, and doing so quickly could make a difference right away. For example, now that Congress has extended the tax subsidy for wind energy projects, Treasury and the I.R.S. could quickly publish the fine print to make clear what it takes to qualify this year. Thirty members of the Sustainable Energy and Environment Coalition in the House have written that without a quick clarification, uncertainty will continue to impede some wind projects.
None of this will come without a fight, as the president's harshest critics made plain.
"President Obama seemed more concerned about climate change than job creation," said Thomas Pyle, president of the Institute for Energy Research, a nonprofit that promotes free-market energy and environmental policy. "For this administration, a deadly hurricane means a chance for carbon taxes. A crop-killing heat wave means another opportunity to attack the coal industry."
In the official Republican respponse, Florida Sen. Marco Rubio stressed the importance of fossil fuels. "God also blessed America with abundant coal, oil and natural gas," he said. "Instead of wasting more taxpayer money on so-called 'clean energy' companies like Solyndra, let's open up more federal lands for safe and responsible exploration."
House Speaker John Boehner also weighed in with a detailed rebuttal of the president's climate remarks. "The Obama administration's so-called 'green energy' agenda has destroyed jobs at home, shipped jobs overseas and left American taxpayers holding the bag for millions of dollars in failed pet projects," Boehner said.
The president is not without allies; but their path remains unclear.
Rep. Henry Waxman (D-Ca.) and Sen. Sheldon Whitehouse (D-RI), both crusaders for action on climate, are putting together what they call a "bicameral climate change task force" to solicit ideas from a wide range of actors. And six scientific societies are calling on the president to convene a climate summit.
Senators Barbara Boxer of California and Bernie Sanders of Vermont, meanwhile, said they would unveil comprehensive legislation on Thursday that would impose a fee on carbon emissions to pay for much higher spending on conservation and renewable energy.
Despite the costs, not all business groups are opposed.
The Business Council for Sustainable Energy, which represents energy efficiency, renewable energy and natural gas companies, said that even if Congress remains gridlocked "in the short term, clean energy industries will work with the Administration to ensure that commercially-available clean energy technologies are fully utilized to reduce emissions."
One trick will be the administration’s embrace of natural gas and oil drilling on public lands, part of its all of the above approach to transforming the nation's energy landscape.
"The natural gas boom has led to cleaner power and greater energy independence,” Obama said. "That's why my administration will keep cutting red tape and speeding up new oil and gas permits."
In quick reply, the 350.org group dismissed that approach in a Twitter message: "Let's be clear: gas drilling is NOT a climate solution."