Several factors, including La Niña events, have contributed to the expanded drought, meteorologists say. Conditions in the West may be setting up for a 'megadrought' by century's end, researchers warn.
The estimates from the National Research Council, taking advantage of more recent research, range from 19 to 55 inches. The study is expected to become a common frame of reference that coastal communities can use in planning.
Arctic monitoring stations show carbon dioxide levels are now above 400 parts per million. Carbon dioxide is the chief climate-change gas and stays in the atmosphere for 100 years. Before the Industrial Age, carbon dioxide levels were 275 ppm.