Daily Archives: July 22, 2021

Bevy of Black Swans

Cliff Mass likes to refer to the recent heat wave in the Pacific Northwest as a “black swan” event. The term refers to “Black Swan Theory,” developed by Nassim Nicholas Taleb, which wikipedia describes as a “metaphor that describes an event that comes as a surprise, has a major effect, and is often inappropriately rationalized after the fact with the benefit of hindsight.


Here’s how Taleb himself defines a “black swan” event:

What we call here a Black Swan (and capitalize it) is an event with the following three attributes.

First, it is an outlier, as it lies outside the realm of regular expectations, because nothing in the past can convincingly point to its possibility. Second, it carries an extreme ‘impact’. Third, in spite of its outlier status, human nature makes us concoct explanations for its occurrence after the fact, making it explainable and predictable.

I stop and summarize the triplet: rarity, extreme ‘impact’, and retrospective (though not prospective) predictability. A small number of Black Swans explains almost everything in our world, from the success of ideas and religions, to the dynamics of historical events, to elements of our own personal lives.


I stop and emphasize the phrase “not prospective.”


Taleb means that there’s only retrospective explanation, there’s an absence of prospective (i.e. predictive) explanation. I’d like to remind Cliff Mass that extreme heat waves, of greater frequency and severity than seen before, has been a prediction of climate change science for decades. Therefore, according to Taleb’s own definition, the recent heat wave in the Pacific Northwest is not a black swan event.


Taleb emphasizes the folly of “explaining” an extreme event with major effect which nobody saw coming, as though we should have known all along. He’s got a point. I’ll emphasize the folly of the opposite mistake: to use “Black Swan Theory” to dismiss what scientists have been warning us about for decades, as nothing but an unpredictable outlier.


Perhaps Cliff Mass will insist that the heat wave in the Pacific Northwest was so severe, that nobody predicted a heat wave this strong. It was so much an outlier, we have to call it a “Black Swan.”


If we’re going to do that … then there are a whole lot of Black Swans popping up these days. All over the world. With a frequency, and of a blackness, far beyond what we’ve seen before, a veritable population explosion of Black Swans. The heat wave in the Pacific Northwest is far from the only example, but it is the one which Cliff Mass can’t ignore.



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