Are Extremes Increasing?

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From Watts Up With That?

Guest Post by Willis Eschenbach

As the result of an untimely rush of blood to my head, I posted the first comment on an article at PhysOrg entitled On this flooded island of homeless people, climate change has never been more real. Pulling out all the stops to tug at our heartstrings, the article talks about some homeless folks in Sacramento, California who apparently believed the recent drought would last forever. The story was also picked up by the LA Times and other papers. Of course, the LA Times can’t call them “homeless”, that’s not politically correct these days. The term currently used by noble virtue signalers is “unhoused” …

[Lest you think I am without compassion for the homeless, please read my posts “Fixing The Brakes“, “Fixing The EGR“, and “Wandering In Wonderland“. But I digress …]

In any case, here’s the backstory. As a result of thinking the river would never rise again, or perhaps not considering the river at all, a number of the “unhoused” took up residence on a spit of land jutting into the Sacramento river called “Bannon Island”. And of course, 100% predictably, after the last several years of little rain the recent strong rains slowly transformed the spit. First, it turned back into an island, then into a partially-flooded marsh. As the photo above shows, now these unhoused people have to travel to/from their unhouses by raft. Shocking, I know, and obviously a clear sign of “climate change” to the climate ignorati.

My comment was:

When California was dry over the last few years, that drought was blamed on “climate change”, and the people on Bannon Island were high and dry. Mostly high.

Now that we have rainfall again, Bannon Island is partially submerged, and the people on Bannon Island are wet, but likely still high … and that is also blamed on “climate change” …

You guys are a joke. If both wet and dry can be blamed on climate change, then EVERYTHING is the result of climate change. And that’s just nonsensical.

Get a grip. California has had both floods and droughts for untold millennia. And if you live on a low-lying spit of land in a riverbed, you can’t be surprised if the rain may flood your home.



Likely somewhat harsh in retrospect, but I don’t care for folks who turn human foolishness and lack of foresight into some kind of bogus climate morality tale.

Amid the usual mud-throwing personal attacks on me that are the typical response of people who have no scientific ammunition, someone said:

It is pretty clear even to high school students: more energy in a system with high contrasts and processes of mixture leads to increased extremes, on either side. You don’t even need earth science for this, of which much can influence the outcome, exacerbate or dampen events.

To which I replied:

While this may be true in theory, recently in fact there has been LESS annual variation in rainfall in Sacramento. Variations in the 1800’s were larger than today. See here for the actual data. (Note there is missing data for a few of the recent years.)

Unfortunately, the PhysOrg website doesn’t allow images in comments. If they had, I’d have posted up this graphic.

Figure 1. Monthly rainfall, Sacramento, CA. Source: KNMI

Of course, this was not convincing to the gentleman, who once again resorted to a personal attack, saying “It is true in practice and you are not a climate scientist.” I had to laugh at that, given that my work has been cited by the IPCC as well as in a Congressional submission to the EPA, and Google Scholar lists ~ 200 citations to my various scientific articles.

However, it did give me an idea about how I could measure “climate extremes”. I decided to take a look at a trailing standard deviation of the Sacramento rainfall data. “Standard deviation” is a measure of the spread of the data. If we’re currently getting more extremes, meaning more wet years and also more dry years, then the standard deviation of the recent data should be greater than that of the earlier years.

A “trailing standard deviation” measures the standard deviation of some number of years previous to a given year. I used a 30-year trailing standard deviation in the graphic below, meaning that each data point in time represents the standard deviation of the 30-year period prior to that time. Why 30 years? Well, calculations over that length of time are generally said to represent the climate rather than the weather. Here’s the result.

Figure 2. 30-year trailing standard deviation of the monthly rainfall in Sacramento, California. Photo shows one of the unhoused inhabitants of Bannon Island considering the vagaries and peccadilloes of the weather.

“Great,” sez I, “done deal!” … however, as has happened more than once, during the night I woke up and thought “Hang on, I left something out!” Grrr … what I’d left out is the fact that as the average rainfall decreases, as has happened in Sacramento, we’d expect the standard deviation to decrease as well. So Figure 1 was not showing what I wanted to investigate.

Of course, that kept me tossing and turning the rest of the night, until I got up early and redid my calculations by expressing them as the 30-year trailing standard deviation divided by the 30-year trailing mean (average) of the values. This removes the effects of the change in the mean over time. Here’s that result.

Figure 3. 30-year trailing standard deviation of the monthly rainfall divided by the 30-year trailing mean (average) of the monthly rainfall, Sacramento, California.

So that was encouraging. The shape of the curve changed, but the conclusion of decreasing extremes was unchanged.

Upon seeing that I had another thought, viz, “Well, maybe I’m missing short-term increases in extremes that are masked by looking at a 30-year time span”. So instead, I looked at 6-year trailing standard deviations divided by 6-year trailing means as shown below.

Figure 4. 6-year trailing standard deviation of the monthly rainfall divided by the 6-year trailing mean of the monthly rainfall, Sacramento, California.

Clearly, despite generally rising temperatures and “more energy in the system”, the variations in rainfall in Sacramento have been getting less extreme, not more extreme … go figure.

At some future date I might take a look at some other datasets … any suggestions regarding what data might be revealing gladly accepted, but no guarantees. Ars longa, vita brevis …

California rain is important to me because I live in a redwood forest about six miles inland from the Pacific Ocean, an hour and a half north of San Francisco … and the rain continues to fall. Supposed to rain every day for the next ten days, looks like a real frog-strangler. No complaints from me, though, it fills the water table so our water well will produce in the upcoming summer.

My best to all, wet or dry, housed or un,


As Is My Custom: I ask that when you comment, you quote the exact words you are discussing. This lets everyone know exactly who and what you are discussing, and it avoids many of the misunderstandings that plague the Web.