California is on snow, wind and flood watches this month, as the Pineapple Express weather system drives Pacific water to the state. But scientists report the wet weather might relieve the region’s worst drought in 1,200 years.
‘This is California – drought happens,’ says Daniel Griffin from the Department of Geography, Environment and Society at the University of Minnesota. ‘Time and again, the most common result in tree-ring studies is that drought episodes in the past were more extreme than those of more recent eras. This time, however, the result was different. We were genuinely surprised.’
Griffin and his colleague Kevin Anchukaitis from Woods Hole Oceanographic Institute studied recently-released National Oceanic and Atmospheric Administration data on California’s Old Blue Oaks. This let them reconstruct rainfall in the region back to the 13th century. The researchers found that low rainfall levels are not unusual in the state’s history. What’s changed is that low rainfall is combined with sustained record high temperature.
California has also experienced so-called mega droughts in the past, episodes that were interrupted by heavy rainfall. The current drought appears to be worse than previous consecutive drought years without reprieve.
A very wet winter might help California escape drought next year. ‘But there is no doubt,’ says Anchukaitis, ‘that we are entering a new era where human-wrought changes to the climate system will become important for determining the severity of droughts and their consequences for coupled human and natural systems.’