Donald Trump’s decision to withdraw the U.S. from the Paris climate deal has “ignited” widespread environmental activism, musician and campaigner Bob Geldof said Wednesday.

The Live Aid benefit concerts organizer labeled Trump “a vulgar fool” and said the American president’s stance on climate change has encouraged several U.S. states to do more to address the issue.

Geldof is known for his political activism and has previously called Trump a “racist” and a “liar.”

In an interview Wednesday, the 65-year-old told CNBC: “What’s interesting is that, parallel with the withdrawal from the Paris agreement, is that the states and the cities have suddenly ramped up their acknowledgement of the problem, and started implementing far greater regulations than were actually asked for by the Paris agreement.”

Geldof said Trump’s Paris agreement withdrawal had “ignited the issue for the young.”

“They weren’t really captured by the existential threat of climate change,” he said. “But the reality of an oppositional position to the president that they didn’t want, that excited them and so you get a lot of activism now. So bizarrely, the very thing that Trump was denying was immediately accepted because he was denying it.”

In July, Trump declared the U.S. would withdraw from the Paris agreement, sparking an international backlash. A report this month suggested the president may soften his position, although this was swiftly denied by his administration.