PITTSBURGH (KDKA) — Pittsburgh Mayor Bill Peduto said Donald Trump is a bully after the president tweeted about teen activist Greta Thunberg.

Mayor Peduto recently returned from Madrid at the UN’s latest climate change conference.

Teenage climate activist Greta Thunberg was with the mayor at the conference when she was named Time Magazine’s “Person of the Year.”

“I worry about her,” said Peduto. “She’s a 15-year old girl. It’s tough enough being a 15-year old girl, but being surrounded by 200 cameras constantly. I just hope that there’s someone watching out for her.”

One person with a different concern is President Trump, who tweeted Thursday about Greta’s designation.

(Photo Credit: KDKA)

“So ridiculous,” Trump tweeted. “Greta must work on her Anger Management problem, then go to a good old fashioned movie with a friend! Chill Greta, Chill!”

Social media erupted, while Peduto said Trump was using Twitter like he always does.

“The president has chosen, even before he was the president, to use his bully pulpit as a bully,” said Peduto.

After being at the conference, Peduto said he wants Pittsburgh to set the right example in the city’s efforts to reduce carbon pollution.

Mayor Peduto insisted Pittsburgh remains in the Paris Climate Accord, even as President Trump has sought to remove the United States from that agreement.

“The United Nations now realizes that no matter what countries decide to do, the actual implementation of climate change will be done on a local level,” Peduto told KDKA political editor Jon Delano on Thursday.

Part of the focus at the conference was on what cities and towns can do to limit pollution from transportation, large buildings, and other fossil fuel emitters.

“We know that we can at a local level be able to limit or to reduce the amount of carbon that we are putting into the atmosphere,” Peduto said.