A State Department science envoy announced his resignation on Wednesday, citing President Donald Trump’s response to violence at a white nationalist rally in Charlottesville, Virginia and the President’s attitudes toward climate research.

Daniel Kammen, appointed in 2016 as one of the department’s science envoys with a “focus on energy innovation in the Middle East and Africa,” tweeted his resignation letter to Trump.

“Your response to Charlottesville enables racism, sexism, & harms our country and planet,” Kammen tweeted.

In the letter, Kammen wrote that he decided to resign “in response” to Trump’s “attacks on core values of the United States.”

“Your failure to condemn white supremacists and neo-Nazis has domestic and international ramifications,” he wrote. “Particularly troubling to me is how your response to Charlottesville is consistent with a broader pattern of behavior that enables sexism and racism.”

Kammen wrote that Trump’s “decision to abdicate the leadership opportunities and the job creation benefits of the Paris Climate Accord,” which Trump in June announced the United States would abandon, and his behavior “to undermine energy and environmental research are not acceptable.”

“Acts and words matter,” Kammen wrote. “Your actions to date have, sadly harmed the quality of life in the United States, our standing abroad, and the sustainability of the planet.”