U.S. Treasury Secretary Steven Mnuchin took a jab at climate activist Greta Thunberg on Thursday during a news conference with reporters at the World Economic Forum in Davos, Switzerland, reported Reuters.

"Who is she? The chief economist?" Mnuchin told reporters. "After she goes and studies economics in college, she can come back and explain that to us."

Mnuchin's witty remark came several days after President Trump indirectly called climate activists the "prophets of doom."

Mnuchin said many developed and emerging economies are moving towards a much cleaner process of extracting and processing fossil fuels, but calling for investors to "divest" from energy is idiotic at the moment.

Thunberg demanded world leaders and top investors at Davos to immediately divest from energy and transition into the green economy.

Climate change was the dominating theme at Davos this year – the 17-year-old climate change activity said world leaders were doing very little to prevent the planet from burning.

She told Davos attendees that "our house is on fire" as global emissions of carbon dioxide are rapidly rising.

President Trump told reporters as he departed Davos on Wednesday that he would've liked to listen to Thunberg and insisted the U.S. had the greatest "numbers" of clean air and water quality.

The president said Thunberg should concentrate on other countries - a reference to China and India - where pollution is out of control.

"There is a real misinterpretation of the U.S. policy. Let me be very clear: President Trump absolutely believes in clean air and clean water and having a clean environment," Mnuchin said.

And several hours after Mnuchin slammed Thunberg – she responded with a tweet that said, “My gap year ends in August, but it doesn’t take a college degree in economics to realise that our remaining 1,5° carbon budget and ongoing fossil fuel subsidies and investments don’t add up. 1/3.”

My gap year ends in August, but it doesn’t take a college degree in economics to realise that our remaining 1,5° carbon budget and ongoing fossil fuel subsidies and investments don’t add up. 1/3 pic.twitter.com/1virpuOyYG — Greta Thunberg (@GretaThunberg) January 23, 2020

Thunberg added, "So either you tell us how to achieve this mitigation or explain to future generations and those already affected by the climate emergency why we should abandon our climate commitments."

So either you tell us how to achieve this mitigation or explain to future generations and those already affected by the climate emergency why we should abandon our climate commitments. 2/3 — Greta Thunberg (@GretaThunberg) January 23, 2020

And now we wait for a response from Mnuchin...