September 16, 2014

California drought? That's climate change

Both Jeff Masters of Weather Underground and Joe Romm have details in this.

What's called the Ridiculously Resilient Ridge of high pressure, the one that sent wintertime Pacific moisture far, far north of California and continues to affect it now, is influenced by climate change.

Oh, and as for denialists who pooh-pooh computer models? With the aid of computer models, this was predicted a decade ago, Romm notes.

And, it won't get better. Romm, quoting NASA:

… it is important to note that the dipole is projected to intensify, which means more extreme future droughts for California. Historical data show that the dipole has been intensifying since the late 1970s. The intensified dipole can be accurately simulated using a new global climate model, which also simulates the level of greenhouse gases in the atmosphere. Simulations with only natural variability show a weakening dipole, which is opposite to what is currently being observed. Moreover, the occurrence of the dipole one year before an El Nino/La Nina event is becoming more common, which can only be reproduced in model simulations when greenhouse gases are introduced into the system
Romm also quotes Michael Mann noting that the UN's climate change reports have been on the conservative side on issues like this.

Meanwhile, per other modeling, Masters says that research shows that if the "polarity" of this ridge, this dipole, flips, extremely wet years in California — think El Niño winters — could be even more drenched than in the past.

That said, for the next winter, although Masters mentions a likely El Niño, and a likely strong one, ahead, the National Weather Service seems to disagree. Its winter precipitation maps show a modest chance of above normal precipitation in Southern Calfornia, south of Bakersfield, only, and nothing for the north. Those odds go up from modest to moderate from Arizona to West Texas. Still, the NWS maps seem to be saying that if there is an El Niño, it won't be huge.

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