Drought in California and Climate Change: They are linked

A paper just out now in PNAS by Noah Diffenbaugh, Daniel Swain, and Danielle Touma shows that “Anthropogenic warming has increased drought risk in California.” From the abstract:

… We find that although there has not been a substantial change in the probability of either negative or moderately negative precipitation anomalies in recent decades, the occurrence of drought years has been greater in the past two decades than in the preceding century. In addition, the probability that precipitation deficits co-occur with warm conditions and the probability that precipitation deficits produce drought have both increased. Climate model experiments with and without anthropogenic forcings reveal that human activities have increased the probability that dry precipitation years are also warm. Further, a large ensemble of climate model realizations reveals that additional global warming over the next few decades is very likely to create ∼100% probability that any annual-scale dry period is also extremely warm. We therefore conclude that anthropogenic warming is increasing the probability of co-occurring warm–dry conditions like those that have created the acute human and ecosystem impacts associated with the “exceptional” 2012–2014 drought in California.

Read more here: http://scienceblogs.com/gregladen/2015/03/23/drought-in-california-and-climate-change-they-are-linked/