Teen climate crusader Greta Thunberg delivered a thought-provoking speech at the World Economic Forum in Davos, Switzerland, on Tuesday urging an immediate action on climate change as she reminded the world: "Our house is still on fire."

President Donald Trump tore into environmental "prophets of doom" at the Davos forum Tuesday, rejecting fiery warnings from teenage campaigner Greta Thunberg, and lauding the "unprecedented" US economy just hours ahead of his impeachment trial back home.

Activist Greta Thunberg said on Tuesday planting trees was not enough to address climate change, in an apparent rebuke to a pledge in Davos by US President Donald Trump an hour earlier.