"Global warming turned what would have been a moderate 19-year drought into one of most severe 'megadroughts' of the last 1200 years."
"Since 2000, the West has been stricken by a dry spell so severe that it ranks among the biggest "megadroughts" of the past 1,200 years. But scientists have found that unlike the decades-long droughts of centuries ago, this one has been supercharged by humanity's heating of the planet.
Researchers analyzed the dry and wet cycles that have swept across western North America over centuries by examining the ancient records inscribed in the growth rings of trees.
Cores extracted from thousands of trees enabled the researchers to reconstruct soil moisture and examine the West’s hydrological history, including long droughts that appear as sets of narrow growth rings running through the wood.
Using data from trees at 1,586 sites across the region, from Montana to northern Mexico, the scientists identified four other intense droughts, in the late 800s, the mid-1100s, the 1200s and the 1500s."