A study of climate data taken from trees in the Western US reveals levels of drought that were significantly worse than anything experienced in the past century.

The 1930s drought that triggered The Dust Bowl, considered the worst US drought that century, was barely strong enough to make the list of worst droughts, according to scientists at Brigham Young University in Utah, who analyzed the state's climate record back to 1429.

"We're conservatively estimating the severity of these droughts that hit before the modern record, and we still see some that are kind of scary if they were to happen again," BYU geography professor Matthew Bekker said in a statement.

"We would really have to change the way we do things here," he said of what would happen if a drought more severe than the 1930s event were to occur again.

Through analyzing rings from drought-sensitive tree species such as Douglas fir and pinyon trees, Bekker and his collaborators were able to determine drought conditions of the old West.

There were 16 consecutive years of below average stream flow starting in 1703, the researchers reported, adding that the Webber River once flowed at just 13 percent of normal levels and has dropped to as low as 20 percent below normal on at least three occasions.

"The most severe drought in the record began in 1492, and four of the five worst droughts all happened during Christopher Columbus' lifetime," BYU said in a statement.

Compared to centuries past, the 1900s were a century of relatively stable climate in the West. The researchers' analysis suggests that the West's climate usually fluctuated far more than it did in the last century, with each of the five preceding centuries seeing more years of extremely dry and extremely wet climate conditions.

"We're trying to work with water managers to show the different flavors of droughts this region has had," said Bekker. "These are scenarios you need to build into your models to know how to plan for the future."

Bekker and his colleagues published their work in the Journal of the American Water Resources Association.