How a Eurasian steppe empire coped with decades of drought
By Diana Crow The bitterly cold, dry air of the Central Asian steppe is a boon to researchers who study the region. The frigid climate “freeze-dries” everything, including centuries-old trees that once grew on lava flows in Mongolia’s Orkhon Valley. A recent study of the tree-ring record, published in March, from some of these archaic logs reveals a drought that lasted nearly seven decades—one of the longest in a 1,700-year span of steppe history—from A.D. 783–850. Decades of prolonged drought…