Show Me the Evidence

“This scenario portrays a ‘nonrenewable resource crisis.’ It is not a prediction. It is not meant to forecast precise values of any of the model variables, nor the exact timing of events. We do believe it represents the most likely ‘real world’ outcome. We will show another possibility in a moment… The strongest statement we can make about scenario 1 is that it portrays the likely general behavior mode of the system, if the policies that influence economic growth and population growth in the future are similar to those that dominated the last part of the twentieth century, if technologies and values continue to evolve in a manner representative of that era, and if the uncertain numbers in the model are roughly correct.”
Meadows and Randers, Limits to Growth, The 30-Year Update, italics in the original


Last week we defined our time, the Age of Limits, as the 50 year window or so in which the curves of the limits to growth (LtG) model run through their inflection points. To put it in Richard Heinberg’s memorable phrase, it is the age of Peak Everything. The graphic reproduced in that post was first widely disseminated among the reading public when it was published by the National Geographic magazine. It remains iconic in my mind, a laser focused representation of the ecological critique of industrial civilization.

The form the presentation takes is as iconic as the message itself for characterizing our time. Such a mathematical graphic weave numerous strands from the western history of ideas together seamlessly. I am quite sure most Nat Geo readers were able to immediately interpret those curves to understand their message, yet doing so represents a wide array of skills and assumptions unique to the modern mind. The algebraic curve as an expression of a mathematical function comes from Descartes in the 1600s but the idea that we can rationally ask about the future and expect it to unfold in a wholly natural way from the causes and conditions of the past and present is much older. Lucretius is our standard bearer in the western tradition here. The curves were generated using the calculus invented by Newton and Leibniz also in the 1600s but the use it is put to by the MIT team to interpolate trends and sketch out future conditions is only meaningful in the context of statistics and probability as they have been understood since the 1950s or so. These three; the calculus, statistics and probability, are the heavy lifters for most all the mathematical sciences which have so transformed our modern world.

The LtG graphic is iconic also in the sense of a stand-in, a symbol for something else. The actual World3-03 model which embodied the MIT team’s theoretical constructs is not in itself the only model or data set being considered when concerns about collapse are being aired. We will return to this point. That said, for the curious one presentation of the World3-03 model design can be found here and for the curious and computer savvy the full Vensim model can be found here.

What you see is a system science design which captures flows from sources towards sinks at various rates. The spaghetti looking aspect are the interactions between the various systems, the feedback loops that create the overall non-linear behavior the model exhibits. By changing the numeric value of the parameters we ask how the model will perform under different sets of assumptions. The rates and values set according to historic precedent creates the business as usual scenario, what is called scenario 1 in the quote above.

In the books Limits to Growth and Limits to Growth, the 30-Year Update a number of other scenarios are explored which ask questions such as what happens if there is twice the amount of resources available than initially assumed, or what happens if dramatic policy changes are put in place. In general such alternate LtG scenarios adjust the timelines, and the initial drivers sometimes fluctuate between a source crisis (not enough) and a sink crisis (too much) but nothing avoids a collapse once society is in a state of overshoot. This is the “general behavior mode” of the model. I encourage my readers who have not read the source material in these two books to do so. The careful consideration of objections and alternatives conveys the system science reasoning very well. It is not enough to dismiss the critique with hand waving.

Still, by itself the LtG study stands as a single piece of evidence. The question whether or not our existing civilization is sustainable over the next generation or two is the most important question the human species faces. Every person alive today not isolated from world affairs cannot help but wondering about the same question at some level or another. Everyone wonders where this Juggernaut is heading. The 30-Year Update put World3’s core question this way: “How may the expanding global population and material economy interact with and adapt to the earth’s limited carrying capacity over the coming decades?” Such an important question deserves as much careful thinking as we can give it. That requires us to gather more evidence.

Did you catch the important caveat in the quote that started this post? It’s been 12 years since the 30-Year Update was published and looking back it seems clear that neither the “policies” nor the “technologies and values” dominating our societies changed much from those which shaped the “last part of the twentieth century.” That is two of the three ifs mentioned. The final if, on the other hand, remains as relevant as ever; namely, are the numbers used in the model to represent aggregates and facts for which we have little data and are highly uncertain roughly correct?

This is the voice of science. It remains open to new information and correction. Science speaks in P-values, confidence intervals and error ranges when using mathematical data analysis.

The fate of humankind and the ecosphere is sufficiently fundamental that we should be willing to set aside whatever might interfere with clearly and correctly integrating and discussing the evidence. Impassioned political speeches and psychologically manipulative marketing techniques have no proper place in this discussion.

We are not trying to score points, as if this were nothing more than a clash of ideas taken up by a debating team. Our children’s lives hang in the balance. The emotionally manipulative and deliberately disingenuous is, frankly, pathetic and unacceptable and will not be considered any further. This is an adult conversation and they are not invited to a place at the table. Which leaves the seriously concerned to wrestle with the evidence.

The useful engagement with something like the LtG model is using it to sharpen our thinking about the real world. System science models have places of leverage, places where a small force applied can have results far out of proportion to its magnitude; much like the current from a 1.5 volt battery can control the electronic governor of a large industrial manufacturing process. Finding where in the system such points of leverage exist and experimenting with them when they lead to more positive outcomes or protecting them and monitoring them as critical trigger points when they threaten negative outcomes is one way of taking the evidence seriously.

Another is to examine an item such as topsoil loss and work to lower its rate by building up productive soil. The model gives some parameters around what might and might not actually be helpful.

Of course the LtG is only one model on the table. The climate change ecologists are running supercomputers day in and day out. The IPCC models are also on the table, right next to biodiversity graphs, ocean toxicity and all the rest. Those people seated around this table are engaged in a multi-model comparison, a meta-model study. Each model comes with its own uncertainties and the combination of models can potentially introduce more. In fact the greatest uncertainties typically cluster around questions about how one weakened system might react to another system which is slowly failing which itself depends on a system in crisis. All too often that is the state of the real world in all its complexity.

In the heads of every participant another model of sorts is guiding each of them to whatever beliefs they hold about what is really and truly going on. It is the nature of the mind to experience some things as more likely to be real and true than other things. The only question becomes how our convictions were arrived at, whether or not they remain open to new information, and what role reasoning about evidence has played in their formation.

“I recognize a distinction between dream life and real life, between appearances and actualities. I confess to an over-powering desire to know whether I am asleep or awake — whether the environment and laws which affect me are external and permanent, or the transitory products of my own brain.”
H.P. Lovecraft, letter to Maurice W. Moe, dated May 15, 1918

Lovecraft touches on something very profound here. Plenty to chew on from a contemplative point of view but the surface meaning is important to everyone waking up in the Age of Limits. It is interesting to ask ourselves within our contemplation just how willing we really are to sit at this table.

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