Friday, January 26, 2018

Drought? Or Normal?

God speed the plow.... By this wonderful provision, which is only man's mastery over nature, the clouds are dispensing copious rains ... [the plow] is the instrument which separates civilization from savagery; and converts a desert into a farm or garden.... To be more concise, Rain follows the plow.
--Charles Dana Wilber

Since this blog bounces between bicycling for fun to more serious issues such as transportation, health, and climate, I thought I would toss this out in the interest of sustainability issues.

Yesterday the Albuquerque Journal said that "Drought Returns to New Mexico". I would argue it never left. Drought has various definitions and understandings and can be defined on different time scales depending on one's frame of reference (agriculture, climatology, ecology, etc.); it generally means "golly, we are getting less moisture than we have come to expect based on our limited experiences". I tend to think of it in climate cycles, because climate tells us what variations we can expect. As civilizations, we have to manage our societies in light of that expectation. Rain does not follow the plow.

That said, there may be a modern variation to that theme of rain vs. plow that has a lot of credibility: climate change follows the smokestack.

So in the interest of trying to understand what is going on lately as far as that wet stuff that falls from the sky, here are two graphs from a John Fleck article in a 2012 issue of the Albuquerque Journal. Just looking at a century, there appear to be both short (a few years) and longer term (about half a century) cycles.  This is not meant as a prediction or alarm bell, but two things. We can, of course, expect short term El Nino/La Nina/ENSO cycles that mean snowpack/rainfall differences on the year to year basis. We can also expect, if this trend is not an aberration (see tree ring data below), longer term cyclicity in water feast and famine due to physical processes such as the Pacific Decadal Oscillation and other processes, sometimes coupled or that may be teleconnected, such as the PDO and AMO. Note also that if winter precipitation decreases while temperatures increase, this is a double whammy. Snowpack may not last as long due to increased early melting and sublimation. We may see higher transpiration rates in trees that may not be sustainable. Plus, insects such as bark beetles may rev their biological engines faster.

I guess its "ask a climatologist" time. Indeed, climatologists have been studying the underlying causes of "drought" cycles in the US Southwest. Some examples here, here, here, here, and here.

Here is that century long record of precipitation and temperature variation in New Mexico, from John Fleck's 2012 article.

Another way to look at precipitation cyclicity.  Elephant Butte Lake levels, ~1910-2015,  from John Fleck's blog.

Pacific Decadal Oscillation. Pretty similar to the Elephant Butte Lake graph, eh?

Finally, a long term tree ring record based model of precipitation in NW New Mexico, showing century duration cycles, from the International Tree Ring Data Bank.


Steve A said...

Suggesting "longer term feast and famine" seems like a low risk prediction...

Steve A said...

It would be interesting to see correlation between NM rainfall and climate over time exists. It may well be one of those places that gets more rain when world temperatures rise. When I read the news on climate change, I'm often reminded that, just as people don't go into HR because they're good at math, they don't go into journalism because they know beans about science.

Khal said...

From my limited reading, NM was likely to go into persistent drought during climate optimums during the last two millenia. But I would have to go back and refresh my reading.

Here is a reference.

John Fleck was an excellent scientific journalist when he worked for the Journal and would sit with scientists as he wrote his articles and cite them as references. He has since moved on to a faculty position at UNM.