That was one hairy drought, not so long ago. Could it be pinned on our changing climate, or was it another example of the climate’s usual twists and turns, its natural variability? I spoke recently with Richard Seager (Lamont-Doherty Earth Observatory, Columbia University). Seager is lead author of a paper, “Causes of the 2011-14 California Drought,” published in the Journal of Climate. When you need to study something big — a bridge, an airplane, a skyscraper — you build a model before you build it.