A new literature survey and synthesis has some grim news about drought:
Dry periods lasting for years to decades have occurred many times during the last millennium over, for example, North America, West Africa, and East Asia. . . . Climate models project increased aridity in the 21st century over most of Africa, southern Europe and the Middle East, most of the Americas, Australia, and Southeast Asia. Regions like the United States have avoided prolonged droughts during the last 50 years due to natural climate variations, but might see persistent droughts in the next 20–50 years.
Even apart from climate change, there have been very long periods of drought in the American West in the past. It’s probably no coincidence that settlement of the West took place in one of the wetter periods, not during one of these long droughts. After all, who would have wanted to settle there after several decades of severe drought? This means that — again, even apart from climate change — we need to be prepared for lengthy periods that are much dryer, which may mean massive changes in population and agricultural production.