The crew of the Vema and other research vessels also brought back samples. “This is a library of mud,” said Nichole Anest, director of the Lamont Core Repository. She gestured toward high shelving walls bristling with more than 40 miles of sediment cores drilled during those expeditions, some of them from over a mile below the surface of the sea.

Fine-grained red, green and white clays spilled out from opened cores on a nearby display table. “The mud includes remains of millions of tiny foraminifera,” Ms. Anest said, referring to a marine organism that lives both in the water column of the ocean and also in the sediments on the sea floor. “By analyzing the chemistry of their shells, we can determine what the climate was like when they were formed.”

One crucial insight from the core analysis was that Earth’s climate system has been far more volatile than anyone previously thought. It turns out it has a disconcerting tendency to change swiftly and dramatically rather than gradually over time.

A study by Dr. de Menocal of sediments off the coast of Africa showed that the present-day Sahara transformed from a lush savanna teeming with hippos and elephants to a virtually rainless desert in the mere geological blink of an eye (roughly a century) because of a sudden shift in the regional monsoon.

Could something equally disruptive happen now? They are taking that possibility seriously at the tree-ring lab, a long, gable-roofed structure that resembles a museum inside, with maps and cross sections of trees pinned to the walls and sitting on work tables.

“Tree rings are the bar codes of climate,” Dr. Williams said as he entered a room stacked high with polished tree cores. “They show us that the past 20 years in the U.S. Southwest have been as dry as any 20-year period in the last millennium.” Those drought-like conditions have increased the risk of megafires, which have already radically transformed the landscape in large swaths of the West.

Earlier generations of Lamonters may have been content to engage in pure scientific research, without concern for its practical implications. But scientists like Dr. Williams are increasingly focused on helping communities actively prepare for climate change. He is currently using his knowledge of fire and climate to advise officials in California about where best to direct future fire prevention efforts.