Global climate change is another area where extreme statements are made, in this case on both sides of the debate, when there is little in science to defend them. Some things are quite certain. Carbon dioxide levels are rising and our consumption of fossil fuels and deforestation in the tropics are probably the main causes. There is a lot of evidence that the earth’s climate is warming: the glaciers in Alaska are retreating and great egrets are visiting northern Lake Huron. But here the consensus ends.
Climate change is a wonderful example to demonstrate the limitations of science. There are two fundamental characteristics of climate change that make it very difficult to use the empirical (scientific) method to predict the future. First there are simply too many uncontrollable variables — the empirical method works best when you can control all the variables except the one you are studying. Second, and even more significant, is the fact that we have only one planet to observe. If we had 50 planet Earths and increased the carbon dioxide levels on 25 of them, leaving the other 25 alone, we might be able to determine a statistical difference between the two samples. With only one Earth, we are reduced to complex computer models of questionable value, and a lot of guesswork.
Climate change is not about scientific certainty; it is about the evaluation and management of risk. I think it is fair to say that climate change poses a real risk, however small or large. When faced with the risk the logical thing to do is to buy and insurance policy. Unfortunately we have no actuarial science on which to base the size of the insurance premium; this is where the guesswork comes in. Is it worth reducing fossil fuel consumption by 60 percent to avoid global warming? Should we add the risk of massive nuclear energy construction to offset carbon dioxide emissions? What does “worth doing away” really mean? Is it possible that global warming might have more positive effects than negative ones?