“I felt that the whole multilateral world, the international framework for human rights, was just collapsing around me,” Ms. Yamin said.

When, from a meeting room at a United Nations climate conference in Marrakesh, Morocco, Ms. Yamin watched Mr. Trump win the election, she was despondent. She felt that her 30-year career as a government lawyer and climate negotiator had amounted to nothing.

“All of it was going up in smoke,” she said. “I couldn’t tell my clients, I couldn’t lie to the Marshall Islands, that we would fix this.” Ms. Yamin took a year off, spending most of her time in nature therapy classes and camping in the wilderness for weeks at a time.

During her time off, Ms. Yamin began reading about other social movements, like the anti-apartheid campaign and the suffragist movement, that used social mobilization and nonviolent resistance to advance their causes. “I felt that the climate movement was almost unique and fragile, relying mostly on insider tactics and not on movement building,” she said. “It wasn’t relying on the full sets of tools.”

It was this idea that reignited Ms. Yamin’s passion for climate and helped her get back to work. Instead of returning to climate diplomacy, Ms. Yamin joined the nascent Extinction Rebellion movement, a decentralized group that uses nonviolent action and civil disobedience, in 2018.

Initially, Ms. Yamin became the leader of Extinction Rebellion’s political team, using her knowledge of the diplomatic terrain to help the movement be more strategic in its activism and get more funding. Even in her new activist role, though, Ms. Yamin felt she was relying too heavily on her intellectual skills instead of putting her body on the line. When an Intergovernmental Panel on Climate Change report was issued in October 2018, Ms. Yamin was reading the report as activists filled Parliament Square in London. As she saw pictures of young people refusing to move and waiting to be arrested, she thought, “I want to be with them.”

Ms. Yamin spent the following two years working with Extinction Rebellion, organizing and protesting alongside other activists. She stepped down from her role with the group in 2020 because of disagreements with other leaders. Ms. Yamin said she believed the movement was not focused enough on climate justice.