Extreme drought conditions are not as rare as they used to be
The ongoing drought in California has been a part of a lot of headlines recently. Recent rainstorms and the relative success of some conservation measures are leading to the same group of questions: Is the drought over? When will it end? And how will it end?
Instead of looking to the ground, scientists at Stanford University examined the sky. What they discovered is that the "extreme" atmospheric patterns that appeared in the recent past and contributed to California's current drought are not really "extreme" after all -- they're becoming more ordinary.
"... we find clear evidence that atmospheric patterns that look like what we've seen during this extreme drought have in fact become more common in recent decades." -- Stanford associate professor and scientist Noah Diffenbaugh
Low precipitation and high temperatures
In a recent study, Stanford graduate students and scientists examined whether different atmospheric pressure patterns have occurred with different frequency in recent decades.
Their analysis revealed that there had, in fact, been a significant increase in the occurrence of extreme atmospheric patterns in the very recent past. More specifically, the occurrence of atmospheric patterns resembling those that contributed to California's ongoing multi-year drought -- low precipitation and high temperatures -- became much more commonplace.
But while the frequency of atmospheric patterns that result in dryness do appear to be increasing, the patterns associated with wet periods are not declining. So the wild extremes are there but the rain isn't necessarily going away.
"What seems to be happening is that we're having fewer 'average' years, and instead we're seeing more extremes on both sides. This means that California is indeed experiencing more warm and dry periods, punctuated by wet conditions." -- Stanford graduate student Daniel Swain
— Stanford Earth (@StanfordEarth) April 1, 2016