Washoe Lake, in extreme western Nevada a few miles from my house. It's a natural lake that fills a shallow basin in the middle of this valley. It had dried up completely in 2015 after several years of drought (left inset). Last season we got an average winter, which partly filled the lake, but by late September it had largely dried up again (middle inset). Now, however, it's full, with several years' worth of water even if the drought returns. Flooded trees (right inset) show how much the water's risen, and in fact it's come up another foot or so since the picture was taken.

This also illustrates my amusement at the notion that desert areas of the American west are going to become "uninhabitable" due to drying out from climate change. It's just as likely they'll become even more subject to severe flooding. An area (Lemmon Valley) in north suburban Reno, consisting of a shallow basin with a dry lake bed (playa) in the middle, is an example. Not only is the playa filled, but it's overfilled, such that houses around are flooded and likely will remain so till late spring, as there's no place for the water to drain. Now, of course the existence of the playa shows that water _sometimes_ accumulates there, but a flood on this scale hasn't happened since the houses were built!

The flooding in California this season, which has spilled over the Sierras into western Nevada and refilled Washoe Lake, results from a so-called "atmospheric river" of moisture-laden air (more poetically termed the "Pineapple Express") that originates from warm tropical water off Hawaii and flows northeast. Global warming is likely to make for stronger atmospheric rivers, and the USGS has even described a scenario in which the Pineapple Express locks in place for most of the season and turns California's Central Valley into a lake. It _has_ happened once; the governor-elect of California was rowed(!) to his inauguration in Sacramento in 1860.

In fact, the precipitation in mountainous areas in middle latitudes worldwide is subject to large year-to-year variability, and the most likely climate-change scenario is that that variability becomes even more extreme. A nuisance? Yes, especially if you've built next to a playa. But it's a long way from "uninhabitable!"

UPDATE: Sorry, I forgot to make the insets visible to "everyone". Fixed!