by Judith Curry
I just received the reviews on the manuscript I submitted to special issue of the journal Climatic Change, entitled “Reasoning About Climate Uncertainty.” Overall, the review was pretty mild. One comment from the editor was about my paragraph that mentioned “black swans.”
The specific text from my paper:
The framework associated with setting a CO2 stabilization target focuses research and analysis on using expert judgment to identify a most likely value of sensitivity/ warming and narrowing the range of expected values, rather than fully exploring the uncertainty and the possibility for black swans (Taleb 2007) and dragon kings (Sornette 2009). The concept of imaginable surprise was discussed in the Moss-Schneider uncertainty guidance documentation, but consideration of such possibilities seems largely to have been ignored by the AR4 report. A key issue is to identify potential black swans in natural climate variation under no human influence, over time scales of one to two centuries.
The editor’s comment, linked to the last sentence:
Good point, you should elaborate how this would help science, policy
What is a black swan?
The concept of “black swan” comes from Nassim Nicholas Taleb, author of the book “The Blacks Swan: The Impact of the Highly Improbable,” .
The term “black swan” comes from the mistaken assumption that all swans are white. In this context a “black swan” is a metaphor for something that cannot exist. Black swans were discovered in Australia in the 18th century, thereby proving false the assumption that all swans are white. In Taleb’s context “black swans” are rare events beyond the realm of normal exprectation.
From the Wikipedia:
The Black Swan Theory or Theory of Black Swan Events is a metaphor that encapsulates the concept that The event is a surprise (to the observer) and has a major impact. After the fact, the event is rationalized by hindsight.
The theory was developed by Nassim Nicholas Taleb to explain:
- The disproportionate role of high-impact, hard to predict, and rare events that are beyond the realm of normal expectations in history, science, finance and technology
- The non-computability of the probability of the consequential rare events using scientific methods (owing to the very nature of small probabilities)
- The psychological biases that make people individually and collectively blind to uncertainty and unaware of the massive role of the rare event in historical affairs
Unlike the earlier philosophical “black swan problem“, the “Black Swan Theory” (capitalized) refers only to unexpected events of large magnitude and consequence and their dominant role in history. Such events, considered extreme outliers, collectively play vastly larger roles than regular occurrences.
Examples of black swans in Taleb’s context include 9/11, financial collapse, power grid failure, the internet, rapid climate change.
A key element of “black swans” is that while they are unanticipated, in hindsight they events are rationalized to seem obvious (it could have been anticipated with better use of available information). While we seem to be able to learn from recent black swan events, anticipating the next different black swan doesn’t get any easier.
Ten principles for a black swan proof world
An article in the Financial Times posts these principles from Taleb that addresses economic issues surrounding dealing with black swan events (text selected for relevance to the climate issue):
1. What is fragile should break early while it is still small. Nothing should ever become too big to fail.
2. No socialisation of losses and privatisation of gains. Whatever may need to be bailed out should be nationalised; whatever does not need a bail-out should be free, small and risk-bearing.
3. People who were driving a school bus blindfolded (and crashed it) should never be given a new bus. It is irresponsible and foolish to put our trust in the ability of such experts to get us out of this mess. Instead, find the smart people whose hands are clean.
7. Only Ponzi schemes should depend on confidence. Governments should never need to “restore confidence”. Simply, we need to be in a position to shrug off rumours, be robust in the face of them.
8. Do not give an addict more drugs if he has withdrawal pains. Using leverage to cure the problems of too much leverage is not homeopathy, it is denial. The debt crisis is not a temporary problem, it is a structural one. We need rehab.
10. Make an omelette with the broken eggs. We need to rebuild the hull with new (stronger) materials; we will have to remake the system before it does so itself. Let us move voluntarily into Capitalism 2.0 by . . . teaching people to navigate a world with fewer certainties.
Anticipating the climate black swan
Weather has these Black Swans too. It follows that blindly assuming continued warming climate trends will lead to the observation of slightly warmer temperatures year over year may work for a while, until a cold snap like the one that hit the eastern US at the beginning of last winter produced one of the coldest starts to winter in many years.
The recent winter weather arguably qualifies as a climate black swan, since people were predicting increasingly warm winters and the disappearance of snow. Once the anomalous and surprising event occurred, in hindsight the weather was easily rationalized in a variety of ways. The recent Queensland floods are another example, after the expectation of continued worsening drought conditions with climate change.
In an article by Marc Gunther on Climate Policy and Black Swan, which is rather unremarkable, there is one interesting quote:
What does this have to do with Taleb? I’m wary of trying to summarize his worldview but Taleb essentially argues that we know a lot less than we think we know. “My major hobby,” he writes on his website, “is teasing people who take themselves & the quality of their knowledge too seriously & those who don’t have the courage to sometimes say: I don’t know….” In essence, Taleb says we are not very good at understanding the past or present — his first book was called Fooled by Randomness — and that we are downright horrible at predicting the future.
Joe Romm asks the question “Is global warming a black swan?” He says:
Global warming obviously is not a black swan. It is an event “outside the realm of regular expectations” but one can’t say “nothing in the past can convincingly point to its possibility” In my 2006 post, I argued that rapid polar warming and the potential for a melting of the tundra and massive release of methane was a black swan. I suppose, for 99% of policymakers and the media it is a black swan, but in fact even the worst-case scenario for global warming isn’t technically a black swan. We have been warned as much as one could reasonably expect us to be warned, but we choose to ignore the warnings. In fairness, though, there is a massive fossil-fuel-funded disinformation campaign out there trying to convince us that all swans are in fact white. Would it were so.
Schneider et al. have a relevant paper entitled “Imaginable surprise in global change science“, which was published in 1998 before black swans became fashionable. From the abstract:
Decisionmakers at all scales (individuals, firms, and local, national, and international governmental organizations) are concerned about reducing their vulnerability to (or the likelihood of) unexpected events, ‘surprises.’ After briefly and selectively reviewing the literature on uncertainty and surprise, we adopt a definition of ‘surprise’ that does not include the strict requirement that it apply to a wholly unexpected outcome, but rather recognizes that many events are often anticipated by some, even if not most observers. Thus, we define ‘imaginable surprise’ as events or processes that depart from the expectations of some definable community. Therefore, what gets labelled as ‘surprise’ depends on the extent to which what happens departs from community expectations and on the salience of the problem. We offer a typology of surprise that distinguishes imaginable surprises from risk and uncertainty, and develops several kinds of impediments to overcoming ignorances.
Overall, the idea of climate black swans hasn’t been explored very much, but I think it is something that deserves further consideration. I agree that global warming itself shouldn’t be regarded as a black swan, although if some of the more alarming sensitivity predictions were to be true with accompanying extreme weather events, then it might arguably be a black swan.
The black swan concept seems useful in the context of Ferrari’s thesis, namely related to extreme weather events that are the opposite of what you would expect in a warming world.
Back to the Climatic Change article
So after pondering the black swan-climate nexus some more, I have decided to add the following text to paragraph cited at the beginning of the post:
A key issue is to identify potential black swans in natural climate variation under no human influence, over time scales of one to two centuries. This would entail understanding and analysis of the regional climate dynamics of extreme events on timescales of decades to centuries. Such an understanding is needed as the background against which dangerous climate change is assessed. The unexpected cold, snowy northern hemisphere winter (2010/2011) and the flooding (2011) in drought stricken Queensland highlights how our expectations of extreme events in a warmer world can be soundly trumped by natural variability of weather processes. Such variability has important implications for the assessment of dangerous climate change and for reducing vulnerability to weather disasters.