1. The last few days of June 2021 have prompted a significant update in my Bayesian bookshelf for 2050. That’s the imaginary 100-centimeter bookshelf on which I keep mental models of what I expect for that year, with each book getting shelfspace proportional to my current guess as to its probability, and the basic rule that models shrink when their narrators are more surprised than the alternatives. The surprise in this case was the “heat dome” in the Pacific Northwest (specifically 116°F in Portland, OR and 121°F in Lytton, BC). It was announced by cbsnews as a “once in a millennium” event, quoted by Slashdot (news for nerds) as
Pacific Northwest Bakes Under Once-In-a-Millennium Heat Dome – Slashdot
In our historical record of North America’s Pacific Northwest this heat dome registers a statistical standard deviation from the average of greater than 4. In layman terms, that means it falls more than 4 deviations to the right of the center of a typical bell curve (shown below) and that equates to values with less than a 99.99% chance of happening.
In other words, statistically speaking, there is a 1 in 10,000 chance of experiencing this value. So, if you could possibly live in that spot for 10,000 years, you’d likely only experience that kind of heat dome once, if ever.….
2. As some of the commenters note, that’s at least somewhat bogus: it assumes a normal distributed variable over many centuries, which is not very likely. In fact I believe it conflicts fatally with the standard stuff about the Medieval Warm Period, the Little Ice Age (ending in 1850 or so, as our records were about to begin?), and all the rest. Climate is clumpy. On the other hand, we do see a reasonably normal distribution within the current clump. So — how to think about it? As I see it, there are three basic ways to look at this: wobble, slide, and hop. (Really, that’s “just a wobble” vs “just wobble and slide” vs all three.) Each is a narrative with a narrator.
Wobbler: Take it at face value, guys: we’re within a climate clump. That means that values do wobble but the distribution is reasonably normal through the clump (over a century now). So, the heat dome stasis is really enormously surprising but it’s possible and it happened and we don’t need to adjust any priors: it will be equally, or almost-equally, unlikely next year. The improbability shrinks when you remember that “Portland” and “Lytton” weren’t pre-specified: if one in ten thousand places has a one-in-ten-thousand event, that’s okay, right? Right? Well, that doesn’t quite fit: this is one in ten thousand improbability for the occurrence of a (North Pacific) heat dome like this, and there are less than a dozen substitute places, not ten thousand of them. It is not the case that we have independent random variables for each small town or even each substantial city. Still, the point is that this event could just be a random wobble in the data: (“Statistics Means Never Having To Say You’re Certain.”)
I didn’t give the wobbler much shelf-space before, maybe 5%, but now he rather suddenly shrank to around 2%.
Slider: We’re not just within a clump, we’re within a clump in which the temperature has risen a couple of degrees over the past century and it’s still going up.. When people talk about once-in-a-millenium becoming once-in-a-century or once-in-a-decade, surely that’s what they’re usually doing, and until just now that has seemed pretty much adequate, indeed I dominated the shelf, like so:
- Think of the distribution of temperatures in 1880 as a normal bell-curve sort of graph; think of the distribution of temperatures in 2021 as another which is similar but the mean is two degrees up.
- Now, think about a large college classroom (mine, teaching at Colgate in 1990) with a lot of young men and young women. Graph the male heights, graph the female heights: very similar bell curves, but with the means separated by about two inches. Oh, looky here! Almost all the very tall are male.
- In just the same way, if you could look at two distributions of temperatures, from long ago and now, almost all the very high temperatures would be now: that’s the way normal curves normally work. So the kind of graph that the Economist shows here, where extreme highs seem to behave more dramatically than it sounds to say “the mean is two degrees up”, is not a surprise.
I’m reasonably sure slide is part of the problem — in fact I’d give that a 99.9%. But just slide? (Or rather, just wobble and slide together?) Does slide lead me to expect events like this? No, even though I don’t have the data to work out the odds for myself: the event was described as a major surprise to weather forecasters who are certainly well aware of what I just said, but who initially thought that the weather models predicting the crisis must be wrong. This was simply not within their zone of plausible outcomes. In fact that one-in-ten-thousand was based on current data within the models, i.e. based on how far we’ve been sliding. The slide is real and certainly makes static heat domes slightly more probable each year than the year before, but as an explanation for What’s Going On Overall it has to shrink as long as there’s an alternative narrator who is less surprised and does less shrinking. And there is, and we call him
Hopper: Yes, climate is clumpy, we’ve been within a clump, but this isn’t within the reasonably probable values of that clump, so just consider that maybe we’ve hopped out of it into a new clump, a clump in which things like “heat domes” of stalled weather happen with drastically increased frequency.
That’s disturbing, and I tend to downrate it on the grounds that most of the time things keep on keeping on and predictions of phase change turn out to have been motivated reasoning. Still, if I have to downrate wobbler as very improbable and slider as inadequate, then some sort of a hop needs an uptick because they have to add up to very nearly 100%. (I’m always trying to allow 0.00….01% for various extreme improbabilities which I won’t start listing except in desperation.)
3. So — what models are out there that fit with a hop? The main hop model, the only plausible one I’ve got, is that the (polar) jet stream is getting more wiggly, less reliable as a weather-pusher. This model is almost trivial: the jet stream is powered by a temperature/pressure gradient, climate change has been warming the poles more than the equator, so the jet stream weakens, fails in its usual task of guiding the prevailing west-to-east temperate-zone winds. A century ago, says hopper, the heat dome would have been pushed along and scattered by those prevailing winds, but this time they did not prevail. Specifically, that may have to do with the warming of the western Pacific and other incidentals, but generically we can expect this to happen more and more often, even beyond the merely exponential (!) rise that’s due to the part of a normal curve that we’re in.
4. On the failing-jet-stream hypothesis, Hopper is not talking about the temperature shift in itself, simply weather (temperature, humidity, pressure, wind) that doesn’t move along as much as it used to so the local and global averages may stay put as time goes on, the local and global standard deviations may stay put, but the local correlation of each day with the next and with the next week will tend to rise because the weather formations themselves will tend to stay put geographically. (If I’m visualizing correctly; at any rate, hopper is expecting an altered distribution of the daily, weekly, monthly rates of change more than an altered distribution of actual values.)
5. I’ve personally read and talked about the wiggly jet stream notion in the past few years, but I’ve mostly held with Scott Johnson’s view from last February:
Blaming a wiggly jet stream on climate change? Not so fast | Ars Technica “The hypothesis is easy to understand, but it’s far from a consensus.” And there are plenty who don’t buy it and they’re not change-deniers. Sure — it’s a “maybe so, maybe no: plausibility high but data insufficient…probability significant but not so high.” I was giving it about 25%….but that’s when slide seemed sufficient for what was happening.
6. And of course it’s not going to be a consensus even now, but on my Bayesian bookshelf it now gets quite a bit more space than it did. Overall, in advance of the heat wave I’d have been at 5:70:25, and now I’m more at Hmmm…. I’m tempted to say 2:45:53, with hop being slightly dominant in my world-view. Why only barely dominant? Looking at my reactions when I try to set it higher, I think that it’s partially an issue of well-earned modesty: I know that I don’t know much, so I’m not prepared to pull hard against what I see as the prevailing trend. Ouch.
7. Yes, that means I should probably split off that factor somehow to consider it explicitly; after all, my general confidence in Official Professional Expertise went down significantly during the pandemic, after going down from reading Yudkowsky’s “Inadequate Equilibria”, after going down from certain financial events in 2008. For now, I was just going to say 2:45:53. However, I’m in the process of reading Julia Galef’s “Scout Mindset” book and she has various mental exercises, hypothetical questions/statements you can work through to get a better sense of what you really think about something, and in the spirit of her exercises I just asked myself: what if I were talking with a few of the experts who seem convinced that it’s not true, and then with others who seem convinced that it is? I find that I can’t imagine being willing to move hop below 50% no matter what the first group said, but I’d be barely willing to move it up to 90% when talking with the others. So, I’m going to split that difference (50+90)/2 = 70, and go to 2:28:70, more or less swapping slide with hop while maintaining a low epistemic confidence.
8. That leaves me two tasks: one is to try to reduce the level of my ignorance, so I’ve been writing a post about jet streams and other “geostrophic flows”. The other is to put down at least part of my sense of consequences. What trends in future agriculture, forestry, fishing, industry, politics, and war do I now give more weight to, and how does technological change interact with each?
9. Basically, hopper thinks open-ground agriculture is going to be even more difficult than shifter has been expecting. That will push several technological options, already in progress: Fast Company notes, in Is indoor farming about to have its moment?, that “it’s getting harder to grow food outside as climate change makes it more likely that farms face droughts, heat waves, flooding, and other disasters. Corn and wheat and other crops that likely don’t make sense to grow inside will have to find other solutions—such as new varieties that can better resist drought, for example—but for some foods, vertical farming could help fill a gap.” Forbes, in Is The Future Of Farming Indoors? has the same attitude but more of a focus on: “One of Square Roots’ indoor farms, for example, produces the same amount of food as a two- or three-acre farm annually, just from 340 square feet. This yield is achieved by growing plants at 90 degrees, and by using artificial intelligence (AI) to ensure the environment is optimal for each specific plant, including the day and night temperatures and amount of CO2 needed.”
10. And where does that trend stop? Does it stop? In ScienceDirect I see Cellular agriculture — industrial biotechnology for food and materials: “It is somehow surprising that the explicit use of entire plant cells as food has only recently been suggested despite the established practice to exploit tissue and organ cultures of ginseng for food supplement production in Asia.
Plant cell culture medium is chemically fully defined and consists mostly of inorganic ingredients, that is, salts, sugar (usually sucrose) as carbon source and some low concentration vitamins and phytohormones.” So, can we turn sunlight & carbon dioxide into sugar more efficiently than green leaves do? That’s a pretty low bar, and the fact that we don’t want most of the plant makes it lower. At this point, my 2050 shelf has expanded sections on a variety of possible technologies that could be involved in generating corn meal and wheat flour, without corn or wheat fields… and the biggie is AI/robotics/InternetOfThings, with genetic engineering having expanded space too. And that need not be bad in itself, but the road from here to there is kinda bumpy.