Climate change is ‘almost assured’ to cause decades-long droughts in the American Southwest not seen since medieval times, scientists warn in a new study.
by Madeleine Gregory See full Vice article here
In medieval times, the US Southwest was routinely struck by decades-long droughts. Those megadroughts stopped around 1600, but climate change could bring them back.
In a study published on Wednesday in Science Advances, researchers from Columbia’s Earth Institute used climate models to study what caused the megadroughts. Using historical climate data, they determined that two things were to blame: changing ocean temperatures and excess energy trapped inside the Earth’s atmosphere (called radiative forcing)….
“Having paleoclimatic evidence shows you what happened in the past,” lead author Nathan Steiger said over the phone. “It helps verify projections that say the American Southwest is almost assured to have a megadrought in the next few decades.” …
According to the study, the biggest driver of these historical megadroughts were La Niña events, which made the Pacific Ocean unseasonably cold, pushing the storm path north towards Washington and British Columbia. A warmer Atlantic played a smaller role, shifting a high pressure system that blocked storms from rolling over the continental US. “Both a warm Atlantic and a cold Pacific change where storms go,” Steiger said. “They both result in fewer storms going to the Southwest.”