California’s current drought is certainly historic. But how historic is it?
Scientists can use variations in the thickness of ancient tree rings to reconstruct past environmental conditions.
The width of the ring is controlled by temperature and precipitation.
Daniel Griffin / University of Arizona
A group of scientists did that for California.
They created a record much larger than the kind instruments can provide.
NOAA / Via droughtmonitor.unl.edu
Without seeing their results, see if you can place the current drought in its proper historical context.
Mark Ralston / Getty Images
