Megadrought in SW by 2050: news shocks climatologist

Like many other Americans, I have had difficult absorbing the recently published news that megadroughts are scheduled into the future for the Southwest. Just did not want to hear that, read that, learn the details. But because I intend to go back to the Mojave this weekend, after being foiled last weekend, I forced myself to read up on the study released just a month ago.

For my readers sake, I tell myself.

Because yes, the news is bad. A cut-the-crap headline might read:

Endless drought in Southwest by 2050: Study

Think you can see it in a graph. Tell me if I'm wrong. Look at the fall-off in moisture in the lower chart.

Droughtprojections

Yes, this is a projection based on mathematical models that represent the atmosphere, and yes, the climatology is tied to soil moisture, and yes, it's a high-end (8.5 RCP) projection. But on the top panel you see it graphically compared to two other modeling systems, and they are in good agreement. A correlation of .86 in one case, and .85 in another. 

A couple of other notes from the paper: some of the models actually project somewhat wetter winters, but it turns out not to matter to the big picture. Still the region trends towards desiccation.

But forget about the science of drought. Think about the news, about forest mortality, about vast lands of trees, species and subspecies, drying out and dying off. It's difficult. I'm not sure I can.

Helpfully Ken Caldeira, of Stanford and many other institutions, steps in and helps us understand — no matter how difficult the news — in a letter to David Perlman at the SF Chronicle.

These model results are the most reliable model results available in the world today. The models have been tested again and again against a wide array of meteorological observations. 

KencaldeiraIf this was one model saying this, it might be a model artifact, but when nearly every model says more-or-less the same thing, you have to pay attention and believe it might be pointing to something real. 

I have looked at some of this model output before, but when you look at them as graphs of probability distribution functions it doesn’t really mean very much emotionally. 

When you stack these model projections against reconstructions of past climates, the results are so sobering that they have me ready to go out for a drink. 

I remember visiting ruins of American Indian civilizations in the desert southwest, places like Mesa Verde, where large civilizations flourished based on an agricultural foundation. It is thought that the rains dried up in year 1276, and a 23-year drought played a major role in causing this civilizations to fail, leaving us with the ruins we see today. 

If you look at the chart showing rain in the desert southwest (Figure 1), the drought of 1276 is like a little blip compared to what is in store for us. 

As a climate scientist, I sometimes think climate change is something we can just muddle through. I have been concerned about excessive alarmism, thinking that climate change might turn out to be not so bad for the average person after all.  These results have me questioning that complacent attitude.  

It looks like the droughts in store for us later this century will make the droughts that did in the Mesa Verde civilization look like child’s play. 

And after that? Let's just say, Caldeira doesn't perk up. Read the whole thing, if you dare.

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