Some elite US politicians’ denial of the science backing up climate change is worrying, the United Nations environment chief has said, adding that the fight against global warming would continue, even without the United States.

US President-elect Donald Trump has in the past dismissed climate change as a “hoax”, vowing during his campaign to pull the United States out of the Paris Climate Agreement, a deal among nearly 200 countries to curb global warming.

Trump, who won the November election on a range of populist promises to deregulate and revive the energy sector, has appointed to his cabinet climate change sceptics, including oil magnates - moves that have angered green groups.

Erik Solheim, executive director of the UN Environment Programme, said in an interview he was not concerned about oil industry stalwarts in Trump’s cabinet, because they brought experience in handling major energy projects and negotiations.

“However, I am concerned that some elite American politicians deny science. You will be in the Middle Ages if you deny science,” he told Reuters in the Indonesian capital, in response to a question about Trump’s cabinet picks.

Trump has appointed at least three cabinet members who have in the past cast doubt on the science behind climate change.

Oklahoma Attorney General Scott Pruitt, who opposed President Barack Obama’s measures to fight climate change, has been picked to head the Environmental Protection Agency.

Former Texas governor Rick Perry has been appointed to lead the Energy Department, which he once proposed scrapping altogether.

Rex Tillerson, chief executive of ExxonMobil Corp will be secretary of state, the country’s top diplomat.

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The majority of scientists around the world say global warming is causing rising sea levels, drought, and an increase in storms.

Solheim said even though Trump’s environmental policies remained unclear, the battle against climate change would continue.

“If the United States, in the worst case, were to withdraw from the Paris Agreement, we will depend more on China,” he added. “China and… many others will provide the global leadership we need.”

Since the election, however, Trump has said he will keep an “open mind” about the climate deal, and has also met former Vice President Al Gore, a leading climate change activist.