The past 22 years in a drought-stricken portion of North America has been the driest stretch for the region at least since the year Charlemagne was crowned emperor of the Holy Roman Empire, researchers say.
The western United States and parts of northern Mexico are experiencing their driest period in at least 1,200 years, according to a recent peer-reviewed study published in the journal Nature Climate Change.
The scientists used tree-ring records from thousands of trees at hundreds of sites to reconstruct summer soil moisture across the centuries, said Park Williams, one of the authors of the study. Some of the rings were able to give researchers a look at soil moisture dating back to 800 A.D. -- the year Charlemagne was crowned as the first emperor of the Holy Roman Empire.
Replies