Pearls and Irritations

It is commonplace for political and corporate leaders to obfuscate public debate on issues they want to avoid by applying simplistic, linear concepts of cause and effect to events that have multiple causes. In the case of climate change, one wonders how long the media and the public are going to let leaders like Malcolm Turnbull and others get away with this blatant piece of cynical misdirection.

In response to the most recent, devastating bushfires in NSW, Malcolm Turnbull, in the tradition of so many climate change deniers before him, has dragged out the tired assertion that one can’t attribute any particular extreme weather event to climate change. In other words, he is tacitly asserting that we don’t really know that climate change is causing extreme weather events, therefore we cannot assume such events are evidence for action on global warming. It is unfortunate to see some climate scientists and environmental groups lending credence to this piece of cynical manipulation, and not opposing it with clear messages about the causes of events in complex systems like the Earth’s biosphere and the human body.

Consider the example of tobacco smoking and lung cancer. Most people – I suspect – would agree with the proposition that smoking causes lung cancer but if they assumed a neat linear relationship from smoking as cause to cancer as effect they would of course be wrong. We know that smokers in Australia have a higher risk of getting lung cancer than non-smokers, but nevertheless, a majority of smokers do not develop lung cancer. Genetic inheritance, nutrition in early life, drug and alcohol use, work environment, exposure to pollutants and many other factors affect risk of disease in general. There are many known risk factors for lung cancer other than tobacco smoke.

So, how do we discern and describe the causal relationship between smoking and lung cancer? Let me put it this way: the human body is a profoundly complex entity in which the presence or absence of a recognisable disease at any point in time is affected by interactions between multiple factors – all the complex internal biology of the organism, all the elements of the environments in which it functions; the constant interaction between the two. However, if you introduce frequent exposure to tobacco smoke over an extended period into this complex equation, then you are changing one key parameter of the system, a change that impacts immediately on how the organism (the person) functions and gradually, over time (as the smoking interacts with the person’s genetics, cellular functions, lifestyle, exposure to air pollution or what have you) progressively increases the possibility that lung cancer will develop. This is how the causal relationship between smoking and lung cancer works, a link that becomes manifestly clear when we look at populations, not individuals, and see that someone who smokes regularly is nine times more likely to develop lung cancer than a non-smoker; but it not a simple, linear one-to-one relationship.

This way of understanding causality in complex systems is not so difficult to grasp. If you removed all the speed limits on Australian roads you could predict with absolute certainty that the road toll would increase, even though many other factors would still be contributing to accidents. It would still be nigh impossible to predict exactly which individuals would be involved in those accidents. However, the causal relationship between the change in speed limits and the increased number of fatal accidents would be starkly obvious: one key determining parameter of the complex road using system is changed and the result will change in predictable (albeit complex) ways.

What causes weather? There are of course multiple factors involved, which interact in complex ways to produce the weather we actually get: the Earth’s rotation, temperature differences between equator and poles, land masses and oceans, evaporation rates and so on. The human-caused increase in CO² and other greenhouse gases in the atmosphere is changing one key parameter in this complex system – the extent to which the atmosphere retains heat – and this change is interacting with the other causal elements of climate and weather to increase the frequency and intensity of extreme weather events in predictable ways, even though it is difficult to accurately predict individual events.

So let’s be clear. If the increasing frequency and intensity of extreme weather events can only become a legitimate reason for action when a simple, linear causal relationship can be demonstrated between climate change and this particular bushfire, this cyclone, this flood; then that will never happen. As the massive toll of extreme weather events on human health, biodiversity, contagious disease, pollution, destruction of infrastructure, flooding of coastal cities and refugee movement mounts up over the next five or ten years, political leaders like Malcolm Turnbull will still be able to justify their lack of meaningful action by vacuously proclaiming that you can’t attribute any particular extreme weather event to climate change. This is puerile nonsense and an abuse of scientific understanding. It is time we all said so.

Dr Matthew Fisher is a public health researcher, political philosopher and artist. He works as a Senior Research Fellow with the Southgate Institute for Health, Society and Equity at Flinders University in Adelaide.

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