Scientists… measured tree-ring growth from forests that included 800-year-old trees. They learned that snowpack reductions in the late 20th and early 21st centuries were unlike any other period dating to at least the year 1200.
But no more than half of the declines can be explained by natural shifts, the study shows.
Alarmingly, their studies indicate that allocation of water in the western US based on estimates made 100 years ago may no longer be tenable.