US Treasury Secretary Steven Mnuchin said that Greta Thunberg should study economics before speaking on fossil fuels.

"After studying economics at university, she can come back and explain to us," Mnuchin told reporters on January 23 at the World Economic Forum in Davos, Switzerland. The statement was made by the US Treasury Secretary after Greta Thunberg ordered that the investment in fossil energy be stopped immediately.

"Is she an economist? Who is she? I don't understand it," Mnuchin said. He paused for a moment, then said that this was just a "joke".

The administration of US President Donald Trump and environmental activist Greta Thungberg have been discussing indirectly since January 21 during a discussion session in Davos, but the organizers have sought to help avoid a confrontation between the two sides. .

Thunberg harshly criticized US policy at the World Economic Forum, while Trump spoke on January 21 sarcastically "apocalyptic prophets" and "predictions of perdition", while Thunberg was sitting in the audience.

Before leaving the resort town in Switzerland, Trump said he would be "pleased" to meet Thungberg, who Time magazine voted as Person of the Year.

Thungberg echoed the climate warnings in a speech in Davos, emphasizing that it was time to "alert" because "the common home was burning", as she spoke in Davos last year.