Within a few decades, a significant chunk of the US could be in for the worst drought in more than a millennium. That's if we don't change our greenhouse-gas-emitting ways, scientists say: A study co-author says the chance of a megadrought in the central and western US sometime this century is more than 80%, the AP reports. A megadrought is one lasting at least 35 years. The data shows "more convincingly than ever before that unchecked climate change will drive unprecedented drying across much of the United States—even eclipsing the huge megadroughts of medieval times," an outside expert tells the Smithsonian.
The Southwest has an 80% risk of megadrought at the current rate of emissions, but even if we drop to "moderate" emissions, the risk remains high, the Smithsonian reports. Scientists turned to more than a dozen different climate models to examine the future; as for the past, they got information from tree rings, which show how wet each year was. "There are degrees of screwed, and this paper suggests we’re falling off the cliff," another expert tells Slate. Still, we have "ample warning" to make changes, a researcher tells the Smithsonian. "We just need to make serious cuts in greenhouse gas emissions … Otherwise the next generations of Americans are going to have a huge problem on their hands." (Already, California's drought has reportedly meant the loss of 11 trillion gallons of water.)