(CNN) - As environmentalists wait to hear what President Barack Obama will say about climate change Tuesday night, they may be disappointed that one popular proposal won't be mentioned in his State of the Union address.
A senior administration official said the president will not announce regulations on carbon emissions for existing power plants, a standard already in place for new plants and a policy change sought by many environmental activists.
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Last year, the Environmental Protection Agency issued its first limits on greenhouse gas emissions from new coal power plants, but not ones already in place. That came after the administration released new standards on toxic pollutants and mercury emissions from plants in 2011.
The official added, however, that the president has "a number of other tools," hinting that Obama will mention in his speech some prescriptions the White House considers aggressive.
Even if the president doesn't outline a specific plan Tuesday night for existing plants, that doesn't necessarily mean the president will stop pursuing such action, says one environmental expert.
Melinda Pierce, legislative director for the Sierra Club, said her group has been encouraging the president to "announce that bold step" in the State of the Union address, but acknowledged it may come later in his second term.
"Whether or not he actually says the word 'carbon,' I think we will hear at least some broad commitment to moving us from fossil fuels to clean energy," she said.
The president placed a surprising emphasis on climate change in his inauguration address last month, a topic he largely avoided during the campaign. Obama vowed to combat climate change, "knowing that the failure to do so would betray our children and future generations."
"Some may still deny the overwhelming judgment of science," he continued. "But none can avoid the devastating impact of raging fires and crippling drought and more powerful storms."
Pierce said they're looking to see if he dedicates as much "real estate" to climate change in his speech Tuesday night. In his previous State of the Union speeches, Obama rarely used the term "climate change" but addressed ways to strengthen clean energy policies and tied proposals to incentives for job creation.
Pierce said she expects Obama to stay on a similar track tonight, given that the president's larger theme will focus on jobs and the middle class. If he doesn't go into great detail about environmental policy, she said, it won't signal a reversal from his inauguration speech.
"It just makes our campaign to continue to build support all the more important," she said.