STUDY: Megadrought Emerging in Western U.S. is the Worst in 1200 Years

April 19, 2020 at 11:48 pm

The last 20 years have been the driest in over 1000 years according to tree-ring data, and scientists don’t expect conditions to get better anytime soon

O.C. Fisher Lake in San Angelo, Texas, in 2011. Credit: Tony Gutierrez, AP

The Western United States has now entered into a climate-driven megadrought, says a new study out of Columbia University.

For the study, scientists looked at 1200 years worth of tree-ring data and found the last 20 years have been the driest  since 800 AD.

They looked at 9 states from Oregon and Montana down through California and New Mexico. The rings of old growth trees revealed changes in soil moisture levels over the centuries.

Cross section from a ponderosa pine tree from southern Arizona.

They tell the story of dozens of major droughts in the Western half of the United States over the last millenium, but none so dry, widespread and long-lived as the one that began in 2000.

Catastrophic wildfires, decreasing snowpack and dwindling water resources have become the norm for Westerners over the last couple of decades, but with rising temperatures and explosive population growth, this may just be the beginning the researchers warn.

Climate change has increased temperatures in the West by 2.2 degrees Fahrenheit in the past 20 years. Since warmer air holds more moisture, it is increasingly being drawn out of the soil.

M ajor agricultural reservoirs in the region, such as Lake Mead and Lake Powell, have shrunk dramatically. And insect outbreaks are ravaging dried-out forests, making them even more vulnerable to fire. And fewer forests mean hotter temperatures, perpetuating the cycle.

“I think the biggest impact is the West-wide increase in very large and intense wildfires, which will get even worse in a warmer future and perhaps unimaginable during a future megadrought,” Jeff Lukas, with the Western Water Assessment at University of Colorado, told CBS.