Cascades of Contingencies


Fluctuations, unpredictability, and a causal chain so complicated the best we can hope for is a forecast. I am talking about the climate and the strange market place of weather patterns that it throws at us. According to some drastic climate changes in the past may well have been contributing factors in a range of significant historical events, but we need not confine ourselves to the archaeology of weather to see that the smallest disturbance arising from an unforeseen event can lead to a startling cascading effect in our climate.

That climate science has become an interesting mix of the speculative and the empirical may seem problematic to some, but the best recent research has been neatly combining the two. This is leading not to a ‘widely speculative’ or ‘theoretical’ angle on climate science, but to much more tempered approaches to the development of climate oriented public policy. Many climate scientists are bugged by the phenomena of retroactive justification that mars much of the science.

There is no shortage to studies outlining how our natural predictive capacities or the range of our technologies failed to spot some unforeseen event or another. Often our failures are a mix of over dependence on these technologies coupled with human error. In many ways the original event is the easiest bit to understand. In retrospect we are can often deduce the series of convergences that led to the original event, but an interesting phenomenon is that we find it much harder to keep track of the resulting cascading effect.

In large-scale climate events such as the recent flooding in Australia (which is still causing problems) it is not the original event that baffles us, but the sheer pace with which its effects multiply and set in motion a process of minor disasters that cumulatively cause chaos (see how fast this can happen in the current blizzards in the United States). In their recent study on ‘Rescuing ecosystems from extinction cascades through compensatory perturbations,’ recently published in Nature Communications, Professor of Physics at Northwestern University Adilson Motter and his assistant Sagar Sahasrabudhe argued that when it comes to species extinction the perfect storm of perturbations in food supply (arising from climate change), the over-exploitation of resources, the rise of invasive species, and the destruction of habitat sets in motion an irreversible casual link that culminates an extinction event for at least one species along the chain.

This is significant in its own right, but it is the effect that this single extinction event has on those that remain that is striking. It leads to a cascade of further extinction. They insist that the precise nature of this cascade is uncertain rendering any predictive model that does not include the uncertain practically useless in relation to the ‘knock on’ effect of extinction events. This renewed emphasis on the uncertain and the contingent is also found in the recent research of K.C. Armour of the Department of Physics and G.H. Roe from the Department of Earth and Space Sciences at the University of Washington.

In their recent article on ‘Climate commitment in an uncertain world,’ published in the latest issue of Geophysical Research Letters, they examine climate commitment. Predictions of climate commitment, namely an attempt to extrapolate from damage done the degree of warming we are committed to regardless of current changes, are difficult since they are already operating at a staggered pace measuring according to the delayed effect of forces that alter the climate. Although climate commitment is often taken as the minimal condition that most public policy on climate change accepts Roe and Armour insist that the degree of uncertainty is actually increased when we include the fullest possible picture of constraints (such as current aerosol radiative forcing).

In essence undersampling might reduce the degree of uncertainty in our models, but it can never reduce the uncertainty implicit in what is being modelled by eliding contributing factors. At the heart of all these studies are warnings that the renewed interest in discussing climate change in terms of its minimal possible impact is an ultimately misguided affair. Although the more factors we include in our models the less clear the picture will be there is little point in generating a clear picture that only tells half a story. In the end such models will only ever produce perspectives.

Read more great article on Celsias:

Climate Change All Too Visible in Australia

The 20th Century Reanalysis Program

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  • Posted on Feb. 7, 2011. Listed in:

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