Researchers determined the California droughts that have affected the region between 2012 and 2014 have been the worst in 1,200 years.
Researchers looked at National Oceanic and Atmospheric Administration (NOAA) climate data and new tree-ring samples from blue oak trees in southern and central California, which are particularly sensitive to moisture changes and vividly display precipitation changes, Woods Hole Oceanographic Institution reported.
The researchers used the tree ring samples to reconstruct rainfall patterns back to the 13th century, and factored in the NOAA data to determine drought severity. The team also looked at NOAA's estimates of the Palmer Drought Severity Index (PDSI), an index of soil moisture variability.
While dry periods are not uncommon in California's history, the combination of record-high temperatures created the multi-year water shortages that have been ravaging the landscape.
"We were genuinely surprised at the result," said Daniel Griffin, an assistant professor in the Department of Geography, Environment and Society at the University of Minnesota. "This is California--drought happens. 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."
The region has experienced multi-decadal droughts, dubbed "megadroughts,"in the past, but those were most likely balanced out by some wetter years. The current short-term drought was determined to be worse than any past drought that spanned consecutive years.
The findings indicate the natural climate system is linked to human-caused climate change, and these types of droughts are likely to occur again in the future. California is predicted to have an exceptionally wet winter, meaning it would no longer be in a state of drought.
"There is no doubt 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," said Kevin Anchukaitis, an assistant scientist at Woods Hole Oceanographic Institution.
The findings were published in a recent edition of the journal Geophysical Research Letters.
