According to a new study from NASA, the chances of a decades-long dry-spell by the end of the century are very high if current rates of green house gas emissions continue.
These so-called "megadroughts" can last 30 years or longer.
Researchers used several climate prediction models to forecast the likelihood of dry conditions between the years 2050 and 2100.
They found that if CO2 levels continue to rise along the current trajectory, there's an 80% chance of a megadrought in California, the Southwest and the Great Plains.
During such a period, those regions would not only see reduced rainfall, but higher temperatures would also likely suck out whatever moisture managed to sink into the soil.
The researchers called this the 'business as usual' emissions scenario, since it assumes little is done to curb greenhouse gas emissions.
The team also drew up predictions that assume humans somehow found a way to stop CO2 levels from rising after 2050.
Even in that scenario, there’d still be a 60%chance of megadrought in the next century. Currently, the regions faces a 12% chance of a prolongued drought, according the the study.
Lead author Ben Cook, climate scientist at NASA's Goddard Institute for Space Studies, said in a press release that over the last century longer droughts typically lasted a decade or less.
"What these results are saying is we're going to get a drought similar to those events, but it is probably going to last at least 30 to 35 years," he explained.
Based on records of drought detected in ancient tree rings, scientists believe North America saw similar naturally occurring megadroughts between 1100 and 1300.
The droughts of the next century could be even worse, said Kevin Anchukaitis, a climate scientist at the Woods Hole Oceanographic Institution who was not involved with this study.
The dry periods of the medieval era are suspected to have had "profound ramifications" for humans living in the Southwest at the time, he explained.
"These findings require us to think about how we would adapt if even more severe droughts lasting over a decade were to occur in our future."