At the conference, it wasn’t clear which camp was coming out on top.

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Each December, more than 20,000 scientists who study the Earth system—seismologists, geochemists, climatologists—assemble for the AGU fall meeting in San Francisco’s Moscone Center, a set of three cavernous convention centers in the city’s financial district.

It is an incredible sight. Researchers in flannel and marmot fleece spill out of auditoriums, meeting rooms, and nearby Starbucks shops. They fill a hall as large as a city block with dozens of rows of poster presentations. They talk about invigorating questions in science—seemingly basic queries like how the moon formed and whether global warming makes Western wildfires more likely.

This year, too, they talked about politics. On the first day of the conference, a set of climate scientists talked to a packed room about how best to communicate the reality of global warming. Naomi Oreskes, a historian of science at Harvard University and the co-author of Merchants of Doubt, urged researchers to keep their public messaging on the issue simple.

“For us as scientists, simple feels simplistic. This leaves people confused, and it leaves the door open for climate-change denial,” she said. The solution was for researchers to just get over their fear of telling simple, emotional stories.

“Communicating science is not the same as doing science,” she said. The standing-room-only crowd nodded along.

The next day of the conference saw a less docile gathering. At noon on Tuesday, climate-activism groups held a protest to assert the reality of climate change and “stand up for science.” The rally was well advertised, and it was easy to get to, held at noontime only two blocks from the convention hall.

It was a frightening time for climate scientists. The Trump transition team had recently sent a lengthy questionnaire to members of the Department of Energy’s civil service. The team sought the specific names of employees who studied climate issues for the government or who had accompanied Obama-era political appointees on trips to international climate meetings. The survey suggested that the new administration would fire scientists just for doing their job. The protest was an easy way to register their discontent.

The rally’s “stage” was impressive. Scientists in white lab coats stood on steps of a Catholic church and held signs saying “PROTECT OUR COMMUNITIES, STAND UP FOR SCIENCE,” and “ICE HAS NO AGENDA—IT JUST MELTS.” Organizers had lined up an impressive set of speakers. Yet when the rally began, only a couple hundred people stood in the square.

“The bottom line is, we don’t want to be here. None of us want to be here. We want to be in our labs, we want to be in the field, we want to be with our students,” said Oreskes to the crowd from the rally stage.