Nestled in the forest behind a guard house just north of the border between New York and New Jersey off Route 9W is one of the world’s greatest meccas for climate change research. Here, perched on the lip of the Palisades, a half-hour north of Manhattan, is a sylvan 180-acre campus where researchers have helped to untangle mystery after mystery. No other geoscience lab was as influential… as Columbia University’s Lamont-Doherty Earth Observatory. …”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.