US President Donald Trump has told the UN General Assembly that climate change was “the greatest con job ever perpetrated on the world”.

Addressing the global body at its New York headquarters on Tuesday (Wednesday AEST), he scoffed at past predictions warning of global disaster from climate change.

The vast majority of climate scientists have concluded climate change is happening, and that it is mainly caused by fossil fuel pollution.

Already, the world is seeing its effects: Floods are becoming more extreme and deadly, droughts are more widespread and severe and heat waves are more dangerous.

But Trump refused to be swayed and dismissed the scientific evidence.

“All of these predictions made by the United Nations and many others, often for bad reasons, were wrong,” Trump said. “They were made by stupid people.”

“They said global warming will kill the world, but then it started getting cooler. So now they could just call it climate change, because that way, they can’t miss. It’s climate change, because if it goes higher or lower, whatever the hell happens, there’s climate change.”

The US president also claimed green energy policies allow countries without restrictions to make money.

“The primary effect of these brutal green energy policies has not been to help the environment but to redistribute manufacturing and industrial activity from developed countries that follow the insane rules that are put down to polluting countries that break the rules and are making a fortune,” Trump said.

He also called the carbon footprint, or the amount of greenhouse gas emissions someone or something produces, a “con job,” arguing that those who pushed for reducing it, such as former US president Barack Obama, were hypocritical in their actions.

“The carbon footprint is a hoax made up by people with evil intentions, and they’re heading down a path of total destruction,” Trump said.

“A few years ago, I remember hearing about the carbon footprint, and then President Obama would get into Air Force One, a massive Boeing 747, and not a new one, an old one with old engines that spew everything into the atmosphere.”