Obama pledged Monday to respond to what he called "the threat of climate change," saying the failure to do so would be a betrayal of the nation's children and future generations.
"Some may still deny the overwhelming judgment of science" that global warming exists and has human causes, Obama said, "but none can avoid the devastating impact of raging fires and crippling drought and more powerful storms."
The president has pledged to boost renewable energy sources such as wind and solar power, along with more traditional energy sources such as coal, oil and natural gas.
"The path towards sustainable energy sources will be long and sometimes difficult. But America cannot resist this transition. We must lead it," Obama said.
Environmental groups praised the mention of climate change, a topic virtually ignored during the presidential campaign. They said they will insist on Obama keeping his promise to make climate change a top priority in a second term.
A key test could be the proposed Keystone XL oil pipeline that would run from western Canada to the Texas Gulf Coast.
Obama blocked the pipeline last year, citing uncertainty over the project's route through environmentally sensitive land in Nebraska. The State Department has federal jurisdiction because the $7 billion pipeline begins in Canada.
Republicans and many business groups say the project would help achieve energy independence for North America and create thousands of jobs.
But environmental groups say the pipeline would transport "dirty oil" from tar sands in Alberta, Canada, and produce heat-trapping gases that contribute to global warming. They also worry about a possible spill.
"Starting with rejecting the Keystone XL pipeline, the president must make fighting global warming a central priority," Margie Alt, executive director of Environment America, said Monday.
Alt and other environmental leaders said they are counting on Obama to set tough limits on carbon pollution from coal-fired power plants and to continue federal investments in renewable energy sources such as wind and solar power.
Obama tried and failed in his first term to get a climate change bill through Congress. Efforts for a new climate bill would trigger major resistance in Congress, especially in the Republican-controlled House.
Scott Segal, an energy lobbyist who represents utilities and natural gas drillers, said Obama "missed the opportunity to remind listeners that climate change is an international phenomenon" that will require international solutions.
By imposing "inflexible" national policies to curb climate change, Obama could restrain the U.S. economy without delivering promised solutions, Segal said.