Before he became President, Donald Trump once called climate change a "hoax".

He came close to repeating that claim on Tuesday.

Trump compared climate change activists to "prophets of doom".

At a time when countries are under pressure to reduce the amount of carbon dioxide they put into the atmosphere, he boasted about America’s "vast" oil and gas reserves and indicated his determination to keep exploiting them.

In his keynote speech President Trump said: 'This is not a time for pessimism. This is a time for optimism.' Credit: AP

It was a remarkable speech and it is remarkable that the Australian government, which sees the recent bush fires as evidence that it is a victim of climate change, couldn’t bring itself to criticise it.

Australia’s finance minister, Mathias Cormann, was in the audience at Davos.

He defended Trump’s address, describing it as "a great speech, a fantastic speech".

Australian finance minister refuses to criticise President Trump's views on climate change, despite Australia wildfire crisis:

As far as President Trump is concerned, it’s business as usual.

As if to make the point he had dinner on Wednesday night with the bosses of the big oil and gas companies BP, Shell and Saudi Aramco.

President Trump position on climate change is at odds with international consensus, it’s at odds many American companies and it’s at odds with the science, which is clear and warns that mankind faces a climate emergency.

Trump at Davos: How much of a blow are the president's comments to the climate change agenda?

The question is can the world avoid catastrophic levels of global warming without the cooperation of the United States, the world's second biggest emitter of carbon dioxide?

The Paris Agreement still holds but most countries aren’t on course to hit the targets they set themselves to eliminate their carbon footprints.

Net zero by 2050 is what we need to hit.

It currently looks impossibly difficult.