US President-elect Donald Trump has famously said climate change is a hoax invented by the Chinese to erode the competitiveness of US industry, and that he wants to disband the powerful Environmental Protection Agency (EPA) and lift "job-killing regulations" on the energy industry to bring back fossil fuel.
So eyebrows were raised when former vice-president Al Gore - who put climate change on the American policy map and won a Nobel Prize - strode into the lobby of Trump Tower in New York on Monday to meet Ms Ivanka Trump.
There is speculation that Mr Trump's 35-year-old daughter may adopt climate change as her cause celebre. She moves in liberal circles socially, and recently met Hollywood actor Leonardo DiCaprio, who apparently gave her a copy of his recent documentary on climate change, Before The Flood.
Mr Gore, after meeting both father and daughter, was non-committal when quizzed by journalists camped in the Trump Tower lobby: "I had a lengthy and very productive session with the President-elect. It was a sincere search for areas of common ground."
Last week, Mr Trump's chief of staff Reince Priebus said the President-elect would keep an open mind, although his "default position" on climate change was that most of the scientific evidence was "a bunch of bunk".
Mr Trump's pro-jobs deregulation and energy agenda, as well as his views on climate change, have long worried environmental groups. "If Trump does try to undermine climate action, he will run headlong into an organised mass of people who will fight him in the courts, in the states, in the marketplace, and in the streets," wrote Mr Michael Brune, executive director of the Sierra Club, the US' largest and most influential environmental network in a blog post on Nov 10.
Mr Trump's first days in office will be a litmus test of his priorities - specifically the US$3.8 billion (S$5.4 billion) Dakota Access oil pipeline.
Running under a Missouri River reservoir, the 1,886km pipeline project has been the focus of unprecedented protests for months by a coalition of Native American tribes. As winter blizzards set in, a camp of protesters at the site has not dwindled but grown - opposing the pipeline on worries it infringes on ancestral lands, and an accident would affect water supply for thousands.
This week, the army, which must issue a permit for the pipeline, declined to do so, in effect punting the ball into Mr Trump's hands.
Trump transition team spokesman Jason Miller told the Associated Press on Monday that the President-elect supports construction of the pipeline, but would review the situation "and make the appropriate determination".
On the same day, Reuters reported that advisers to Mr Trump on Native American issues advocate freeing millions of acres of tribal lands from federal controls to open them up to exploration for mineral resources.
University of Virginia environment law professor Jonathan Cannon, formerly a senior official at the EPA, told The Straits Times that given Republicans' control over Congress, "a lot of damage can be done" to environmental regulations.
While Mr Trump could direct the EPA to amend or rescind regulations, he would have to explain each case convincingly to a court citing scientific data, said Prof Cannon.
Mr Trump has also indicated he could walk away from the Paris Agreement on climate change, which commits countries to curb carbon emissions to limit global warming. He could simply "choose not to do anything to implement the treaty", Prof Cannon said.
"He would face backwash from other countries but there are no penalties."