According to tree ring data provided by Qilian juniper samples from Qinghai province on the Tibetan Plateau, it seems that between a.d. 350 and 370, eastern Asia suffered a “megadrought”—which remains the worst drought recorded in the last two thousand years. The skies simply dried up. Northern China endured conditions at least as severe as those of the American dust bowl in the 1930s, or the Chinese drought of the 1870s—when
