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 U.S. President Donald Trump an hour earlier.

Trump dismissed "perennial prophets of doom" on climate change in his keynote address. While he did not directly name Thunberg, she was sitting in the audience for his speech.

Trump announced the United States would join an initiative to plant one trillion trees, but also spoke at length about the economic importance of oil and gas and called climate change activists the "heirs of yesterday's foolish fortune tellers".