Mr. Trump, who has claimed that global warming is a hoax, said this week in an interview with The New York Times that he now saw “some connectivity” between humans and climate change, and that he would “keep an open mind” about whether to pull out of the Paris climate accord, as he threatened to do during the campaign.

Yet at the same time, some key positions on his transition team are occupied by people with a long history of rejecting the overwhelming scientific consensus on climate change.

Other than climate change, there are numerous environmental issues that he has never talked about and that he might be content to leave untouched. And once agency heads are in place, they may choose very different tactics from those discussed during Mr. Trump’s campaign or by his advisers. Two people considered to be in the running to head the Environmental Protection Agency — Jeffrey R. Holmstead, an energy lobbyist, and Robert E. Grady, a venture capitalist — also have experience in the complex machinations of the federal government.

“Every new administration comes in with an overestimation of what it can accomplish and how quickly it can accomplish it,” said Kevin Ewing, a partner at Bracewell, a Washington law firm.

If Mr. Trump does decide to withdraw from the Paris agreement, he will find it difficult: The accord went into force this month. He would also encounter tremendous obstacles were he to try to dismantle the E.P.A., another campaign threat.

But he may have an easier time abandoning other climate initiatives, including a United Nations-backed program to reduce the environmental impact of international air travel beginning in 2020. The United States has only informally committed to participate in the program, and the new administration could refuse to make that commitment legally binding.

One of the most powerful methods to hobble Mr. Obama’s domestic environmental initiatives would be to block financing for the E.P.A. and other agencies.