In my last column I wrote about the significance of our very warm winter and what it means to the natural water regime upon which we so profoundly rely. This time I want to explore several issues related to precipitation. Be forewarned – this is another “tough love” column. I want to introduce some difficult facts we are going to have to face.
By most accounts, we are now in the fourth year of a “drought.” By this, we mean an exceptional period when our average precipitation fails and we are left unnaturally short of water. Everyone is waiting for the drought to “break” and for conditions to return to “normal.”
But what if this isn’t true? Is there any evidence that suggests that what we think is exceptional may instead be a new long-term pattern? Sadly, the answer is yes.
I regularly read that our current series of dry years (I’m going to step away from the word “drought” for a few paragraphs) is “unprecedented.” I frequently see two arguments for this assertion.
The first is that we have not had four successive years this dry since we started keeping modern weather records in California in the second half of the nineteenth century. The second argument is that tree rings and other data collected from nature suggest that California has not been this dry for a millennia or so.
The problem with these arguments is that the periods involved – even the thousand-year term – are not long enough to capture the full unpredictability of California’s highly variable climate.
Sadly, there is substantial precedent for our current situation. To find it, all one has to do is take a look at the huge amount of data scientists have collected in recent decades about the climate history of California. Such information can be found in the growth rings of trees, silt layers in natural lakes and bays, and even pollen samples taken from the lower levels of mountain meadows.
All this information adds up to tell us some fascinating – and truly scary – things.
The first fact is that the past century – the time we tend to look back on as “normal,” was one of the wettest periods in California in the last seven thousand years.
Another fact is that there was an astounding prolonged dry spell in and around the ninth and tenth centuries (850-1090) and another half a century later (1140-1320). Note that these two events persisted (respectively) for 240 and 180 years. In addition, over the past thousand years, there have been repeated dry spells of 10-20 years duration.
Ponder these two “droughts.” Those who lived through them – the native people of California were already long established then – surely didn’t see them as temporary dry spells. These long periods of dryness were simply the way things were.
And there’s more. Going back further into time. Between 5,000 and 10,000 years ago, the Sierra Nevada was so much drier than now that areas that currently support dense forest had only scattered pine and sagebrush growing on them. That was also, we should note, a period that saw temperatures like those we are moving toward very rapidly as the climate warms.
All this, by the way, has been written up repeatedly by climate scientists and paleoecologists and also generally ignored by both our elected officials and the voting public.
And here’s another troubling fact. The region that adjoins California to the east – the Southwest – has been in a “drought” now for sixteen years. The big reservoirs on the Colorado River – Lake Powell and Lake Mead – are both so low that their managers do not see them filling again in the foreseeable future. Many folks there have stopped talking about “drought;” instead, they’re looking at their difficult situation as a new reality.
Could the same things happen here? Perhaps they already are. And are we ready to talk about “new realities?” Perhaps it’s time.
Notice that I’ve gotten this far without even mentioning climate change. In my last column, I wrote about how our warming climate is likely to drastically reduce snowpack runoff. That’s what happened this year. But what will happen to our precipitation?
The answer, quite honestly, is that no one knows for sure. What the climate models do say, however, is that we should expect continuing warming and more extreme weather events – both bigger storms and longer dry spells. This is exactly what seems to be happening in California.
Where does all this leave us? I believe that it’s time to move beyond our current model of seeing ourselves as suffering from an exceptional “drought” that is likely to end soon and return us to “normal.” We might well be at the beginning of a prolonged dry cycle – a new reality. Perhaps it will last 240 years – no one really knows.
It’s time to face the possibility that dry weather is our “new normal” and that our circumstances are not merely temporary.
Will we ever see a wet winter again? The answer almost certainly is yes, but how such a winter will work is highly uncertain. A pattern of increased drought with occasional intense floods might not be a bad starting point.
California now has almost 40 million people living within its borders, but it still also has large and rich remnants of its natural ecosystems. Our civilization has yet to deal with how to live in California if it turns dry for decades or longer, but this is not true of nature.
The natural systems of California that are here today exist because they were able to survive the challenges of the past including prolonged periods of aridity. What can they tell us?
We’ll explore that question in my next column.
© Wm. Tweed