For me what stands out about June’s feature articles is that the article that sparked the most debate was Mike Pope’s offering. Presumably it had to do with the fact that he sought to debunk Plimer’s climate change scepticism.
For some time now I have been intrigued by the AGW debate, I have been intrigued by the confident assertions that limiting concentrations of CO2 in the atmosphere to so many parts in the million will halt global warming. Then there are those who deny either AGW or just plain global warming and again with the same blind confidence. It seems that this debate highlights some basic shortcomings in the way we understand the notion of scientific objectivity.
Apart from philosophers of science very few of us spend a great deal of time in reflecting on how we assess scientific knowledge. Our shorthand view appears to be that science “proves” the truth and falsehood of particular statements of fact. Clearly the assertion that global warming is caused by human activity is a statement that is either true or false. The majority of us rely on our scientists to tell us whether or not it is true or false. But here we encounter our first problem: not all scientists agree on whether this is true or false so what do we do? Can a statement be both true and false? Given that science is objective does it not follow that we need to have universal agreement? Is doubt consistent with scientific belief?
When people are introduced to scientific reasoning they are generally introduced to four concepts: determinism, empiricism, testability and parsimony. Generally speaking these four are sufficient to understand most of the work that is carried out by scientific research yet when it comes to thinking about global warming these four fall well short of providing us with the tools we need to understand this debate.
In our high school science course we were generally taught that science is about joining the dots - if all events are caused then the role of science is to identify precisely what causes can be assigned to which events. Rarely is there any discussion about the possibility of uncaused events. Equally the examples with which we are confronted tend to be relatively straightforward - dropping a brick out of a window is a good example of cause and effect. The problem is that many events are the product of a complex chain of events so how does one decide what are the determining factors?
Empiricism is supposed to be a help in that regard. We rely on our senses to observe the world around us. From those observations we should be able to work out the relationship between possibly unrelated events. This works well when we simply rely on our own senses but even then we are faced with a rather fundamental problem: what if there are events that are incapable of being observed by our senses? How much of our understanding of the natural world is mediated by a variety of instruments such as microscopes?
When it comes to climate change we have a problem of time - over what period should we be considering our observations? Here the problem is complicated by the fact that the weather observations that have been made over time were scarcely of a consistent quality and even these span over a period of roughly 300 years: 300 years in the life of a planet that is measured in billions of years. So again we do rely not on direct observations but on the inferences we can make by looking at the geological record.
Understanding the history of climate change is forensic science at its most elegant. For example, analysis of Antarctic ice cores show that levels of carbon dioxide and methane in the atmosphere are now higher than they have been for the past 650,000 years while the rate of increase over the past 100 years is greater than at anytime over the past 20,000 years. When we consider that evidence we note that the rate increase over the past 100 years has been keeping pace with our industrialisation one is tempted to the conclusion that there is a link between human activity and current climate change.
But how can we be persuaded that the historical record gives us an insight into what the future holds? The moment we attempt to use this data as a basis for determining what the future looks like we are confronted with the fact that we are dealing with a dynamic system. At best all that we can say is that, if we continue the way we are, future generations will be facing consequences that will be anywhere from mildly uncomfortable to catastrophic. There are simply too many ifs and buts to be confident about what the future holds.
This brings us to the third element of scientific reasoning: that of testability. Much of the debate about whether or not climate change is caused by human activity could easily be resolved if there was some form of testing the hypothesis. But what experiment can one run to demonstrate whether or not the AGW hypothesis holds? Any computer-generated model will be open to question because of the limitations inherent in modeling of all sorts. If questioned I suspect that the majority of people will quite rightly be suspicious of any future forecasts; intuitively we know that we simply do not have the ability to predict conclusively what is going to happen to the earth’s climate in a 60-year period. Paradoxically the longer the time line the more likely that the predictions will be reasonably accurate, the problem is that it is of little value for us to know what the climate will be like in the distant future for there is no guarantee that there will be any humans around to make the observations.
The fourth element of scientific reasoning that of parsimony is what most scientists rely on. Parsimony demands that we embrace the theory that provides us with the simplest explanation that fits in with our observations. It is this principle that has been guiding the advice that scientists have been given to politicians - while it could be a coincidence that the rise in CO2 levels corresponds to global industrialisation the fact remains that when one plots the growth in CO2 in the atmosphere against industrial growth one is struck by how closely the two correlate.
Yet the sceptics are right - none of this represents a knock down argument in favour of any particular policy. In fact I would argue that as long as we are deluding ourselves that this debate can be resolved by an appeal to science we are ignoring the real substance of the debate; for at its heart it is a debate about the sort of choices that governments should make. Those choices may be informed by science but they cannot be made by science.
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