With so little evidence to work with, David Keith, a Canadian physicist, proposed a workaround: The authors could conduct an “expert elicitation,” taking an anonymous survey about what they expected the evidence to eventually show.

At first, not everyone was willing to go along. Some scientists worried that making what amounted to educated guesses would mislead the public, they told Drilled and ProPublica. Benson and Metz, though, both argued that on such an important matter informed advice was better than nothing.

In the end, the group agreed to take the survey and to keep it off the record — they would “burn it afterward,” Keith recounted, making no mention of it in the official report. When the meeting concluded, some of the scientists popped their bottles of cava in celebration.