About two hours north of Los Angeles, stands an ancient grove of big-cone Douglas fir trees. The telltale signs of decades-long droughts from centuries past lie deep within the trunks of its oldest trees. But inscribed just beneath the bark are traces of the worst drought these trees have ever withstood. …The rings inside the Douglas firs record a continuous climate history stretching back 500 years, nearly five times farther than rain-gauge records. But even though these trees are well adapted to this rugged landscape, they cannot survive without sufficient rainfall and moisture. For some of the trees, their unbroken story may be coming to an end. As a dendrochronologist, I examine tree rings to study climate. A recent study published in Nature Climate Change… concluded that there was probably not a drought as severe as today’s in the past 1,200 years. [to access the full story a NYT subscription may be required]