More evidence we've reached "peak water" in California, by @Gaius_Publius

The concept of "tipping point" — a change beyond which there's no turning back — comes up a lot in climate discussions. An obvious tipping point involves polar ice. If the earth keeps warming — both in the atmosphere and in the ocean — at some point a full and permanent melt of Arctic and Antarctic ice is inevitable. Permanent ice first started forming in the Antarctic about 35 million years ago, thanks to global cooling which crossed a tipping point for ice formation. That's not very long ago. During the 200 million years before that, the earth was too warm for permanent ice to form, at least as far as we know.

We're now going the other direction, rewarming the earth, and permanent ice is increasingly disappearing, as you'd expect. At some point, permanent ice will be gone. At some point before that, its loss will be inevitable. Like the passengers in the car above, its end may not have come — yet — but there's no turning back....

I think the American Southwest is beyond a tipping point for available fresh water. I've written several times — for example, here — that California and the Southwest have passed "peak water," that the most water available to the region is what's available now. We can mitigate the severity of decline in supply (i.e., arrest the decline at a less-bad place by arresting its cause), and we can adapt to whatever consequences can't be mitigated.

But we can no longer go back to plentiful fresh water from the Colorado River watershed. That day is gone, and in fact, I suspect most in the region know it, even though it's not yet reflected in real estate prices.

With Californians crossing their fingers in hopes of a super El Niño to help end the state's historic drought, California's water agency just delivered some startling news: for the first time in 120 years of record keeping, the winter average minimum temperature in the Sierra Nevada was above freezing. And across the state, the last 12 months were the warmest on record. This explains why the Sierra Nevada snow pack that provides nearly 30% of the state's water stood at its lowest level in at least 500 years this last winter despite precipitation levels that, while low, still came in above recent record lows. The few winter storms of the past two years were warmer than average and tended to produce rain, not snow. And what snow fell melted away almost immediately.

Thresholds matter when it comes to climate change. A small increase in temperature can have a huge impact on natural systems and human infrastructure designed to cope with current weather patterns and extremes. Only a few inches of extra rain can top a levee protecting against flood. Only a degree of warming can be the difference between ice-up and navigable water, between snow pack and bare ground.

Climate change has intensified the California drought by fueling record-breaking temperatures that evaporate critically important snowpack, convert snowfall into rain, and dry out soils. This last winter in California was the warmest in 119 years of record keeping, smashing the prior record by an unprecedented margin. Weather records tend to be broken when a temporary trend driven by natural variability runs in the same direction as the long-term trend driven by climate change, in this case towards warmer temperatures. Drought in California has increased significantly over the past 100 years due to rising temperatures. A recent paleoclimate study found that the current drought stands out as the worst to hit the state in 1,200 years largely due the remarkable, record-high temperatures.

• Change won't be linear; there will be sudden bursts at tipping points.
   
• Pessimistic predictions are more likely to be right than optimistic ones.

This [incidence of extreme weather] is "a" tipping point, not "the" tipping point. We have slid into a "new normal" for weather, but please note:

• We're talking only about the weather, not a host of other effects, like extreme sea level rise. I don't think we've passed that tipping point yet.
   
• We can stop this process whenever we want to — or rather, we can force the "carbon bosses" and their minions in government to stop whenever we want to stop them. They have only the power we collectively allow them to have.

It really is up to us, and it really is not too late in any absolute sense. For my playfully named (but effective) "Easter Island solution," see here. For a look at one sure way out, see here.