Climate scientists say increasing global temperatures have driven soil moisture in the Southwest below a critical point, creating a positive feedback loop of hotter and drier conditions.
If history is any indication, the Southwestern U.S. may one day see the level of heavy precipitation it last experienced nearly 30 years ago. But while some experts debate when that could happen, others describe the last three decades as a slow and permanent shift to a new normal of hotter and drier conditions.
Scientists disagree as to when the drought officially began, but most point to between 1994 and 1999. The Southwest has seen at-or-above-average precipitation in just 10 of the last 31 years, setting the clock back to 1993, when torrential rain storms caused widespread power outages and infrastructure damage in Arizona. In the following years, the region has remained dry, driven by a warming Earth that reduces storm frequency and evaporates water before it can recharge subsurface aquifers or runoff into the Colorado River…