Tens of thousands of participants from more than 190 countries and dozens of Indigenous groups are staging two weeks of meetings, protests, and negotiations during this year’s summit, known as COP30. Though no U.S. diplomats are present, Foreign Policy has seen a handful of conference-goers sporting white-and-green “Make Science Great Again” hats. California Gov. Gavin Newsom also made a defiant appearance on Tuesday.

BELÉM, Brazil—This humid Amazonian rainforest city is swarming with all the trappings of a United Nations climate summit except one: a U.S. negotiating team.

BELÉM, Brazil—This humid Amazonian rainforest city is swarming with all the trappings of a United Nations climate summit except one: a U.S. negotiating team.

Tens of thousands of participants from more than 190 countries and dozens of Indigenous groups are staging two weeks of meetings, protests, and negotiations during this year’s summit, known as COP30. Though no U.S. diplomats are present, Foreign Policy has seen a handful of conference-goers sporting white-and-green “Make Science Great Again” hats. California Gov. Gavin Newsom also made a defiant appearance on Tuesday.

The annual climate conference, held this year in Belém, is the first since U.S. President Donald Trump returned to the White House and triggered the United States’ second exit from the 2015 Paris Agreement. This time, Trump has gone beyond withdrawing from international climate diplomacy and is actively working to undermine it. U.S. sanctions threats last month against envoys from countries on the verge of reaching a landmark deal to limit global shipping pollution succeeded in blocking the agreement.

The threat of potential U.S. sabotage hangs over Belém, where countries are negotiating if and how they will speed up climate action.