Well, it has finally rained!
At my residence in Three Rivers we received over two inches of precipitation last Friday night and early Saturday morning. Looking back through my weather log, we have not had that much rain within a twenty-four-hour period since January 2012.
The rain did wonders for my drought-stressed native-plant garden. By the following day I could already see the difference. Drought-withered plants were suddenly perking up. I could find green leaves where I had seen nothing but apparent wilt since June. Even my cactus garden looked happier.
Human morale picked up at the same time. My wife and I left a window open Friday night just to listen to the rain. The sound of water falling from the sky did wonders for us too.
This leads, of course, to the inevitable question: what does all this mean for the coming winter? Will we see a shift in our winter weather toward wetter this year? Is our drought going to be washed away by powerful storms?
The answer is that no one has any real idea.
As you may have read, the National Weather Service issued its winter forecast for the nation several weeks ago. To quote the agency’s news release, NWS scientists are predicting that California will experience “at least a 2 in 3 chance that winter precipitation will be near or above normal….”
This sounds encouraging, but let me caution you. Here in California, over the long run, about 40% of our winters fall into the dry category, with the remaining 60% divided equally between average and wet.
What this means, if you do the simple math, is that over the past several decades we have had approximately a 60% chance each year of having either an average or above-average winter. This, of course, is very close to the NWS forecast that we have a 66% chance of such an outcome this winter.
That said, allow me to throw a further complication into the mix. The logic of long-term weather forecasting is to study past conditions, find periods that are similar to now, and then expect the same thing to happen this time.
This logic makes a big assumption, however. For the same things to happen that happened in the past, then the climate must be the same, and that increasingly is simply not true.
California is significantly warmer now than in the recent past. To quote again from the National Weather Service: “2012 and 2013 rank in the top 10 of California’s warmest years on record, and 2014 is shaping up to be California’s warmest year” (ever).
And that leads us to the most important question of all: Does climate change make us more susceptible to drought?
In response, here’s a quote from a recently-published, peer-reviewed (that means serious science) article in the Bulletin of the American Meteorological Society: Using the best scientific models available, the authors concluded “that the human emission of greenhouse gases has very likely TRIPLED (my emphasis) the likelihood of experiencing large-scale atmospheric conditions similar to those observed in 2013” (extreme drought in California).
Put another way, the best available science is telling us that we should expect more frequent droughts in coming years.
All this science confirms a warning about our weather that your stockbroker may have given you under a somewhat different context — that “past performance is not necessarily indicative of future results.”
So, in the end, no one really knows what will happen this year. With a warming climate, which has heated the Pacific Ocean adjacent to California notably this fall, and with a mild El Niño apparently still chugging along, all bets are off.
In the midst of all this confusion, I’m sticking to the long-term forecast I issue every year about this time – “dry until proven otherwise.” I’ll be very pleased if “otherwise” does assert itself in coming months, but caution remains the best position.
And if we plan for dry and find ourselves wrong, wouldn’t that be nice.
© Wm. Tweed