North America experienced an unprecedented 'hot drought' in the last century, new research shows

Western North America has experienced an unprecedented "hot drought" over the last century, especially over the last two decades, according to new research.

Western North America has experienced an unprecedented "hot drought" over the last century, according to new research that shows the amplification of heat in the region over recent decades.

"Hot drought," a climate phenomenon that occurs amid concurrent heat and drought conditions, has affected the western portion of the continent in recent decades at a frequency and severity that was not seen in the hundreds of years preceding modern times, the paper, published Wednesday in Science Advances, found.

Researchers studied tree rings using a new technique called blue light intensity, which involves shining visible light into the ring on the blue wavelength on the spectrum, Karen King, assistant professor of physical geography at the University of Tennessee, Knoxville, and author of the study, told ABC News. This allows the observers to gather a surrogate measure of ring density from year to year, which is then used for temperature reconstructions, King said.

Estimates from the tree rings can predict the severity of drought index, as well as seasonal precipitation, and allow the researchers to independently investigate the relationship between summer temperature and summer soil moisture, King said.