Louise Linton, the wife of Treasury Secretary Steve Mnuchin, deleted an Instagram post on Saturday in support of Swedish climate activist Greta Thunberg. Mnuchin had recently said at the World Economic Forum in Davos, Switzerland, that Thunberg needed to pursue a degree in economics before calling for the U.S. to divest from the fossil fuel sector.

“I stand with Greta on the issue,” Linton said, referring to climate change. “We need to drastically reduce our use of fossil fuels. Keep up the fight @gretathunberg.”

Thunberg told Mnuchin that “it doesn’t take a college degree in economics to realize that our remaining 1.5° carbon budget and ongoing fossil fuel subsidies and investments don’t add up.”

At the same time, Mnuchin has called his remarks a “joke.”

"The comment I made in Davos is there are a lot of important issues that impact the global economy, and I just hope that we balance these other issues, and we talk about these other issues as much as we talk about the environment." Mnuchin said.

Thunberg has also attracted the attention of President Donald Trump. In a viral speech in September, Thunberg said that ecosystems are collapsing and people are dying due to climate change.

“She seems like a very happy young girl looking forward to a bright and wonderful future. So nice to see!” Trump responded sarcastically.

Thunberg became famous due to her school strike for the climate movement, which calls on school children internationally to skip class to raise awareness about the environment.