Friday, May 20, 2011

Global Warming Objections, Part I: Is Science Ever 100% Certain?

by Chuck Hall
In spite of an overwhelming amount of evidence that human activities play a part in global warming, there are still quite a few people who think that global warming is some sort of vast government conspiracy concocted by scientists. The goal of this ‘conspiracy’ remains unclear. There is still enough opposition to taking action on global warming that it is a major concern for those of us who care about the environment. This week I begin a series of columns examining some of the major objections to global warming and climate change.
Let’s start with this idea of ‘certainty’ about scientific data.
Imagine you’ve gone to the doctor for your annual physical. She runs the usual tests. When the results come back, she has some bad news for you: you have some of the symptoms of cancer.
You ask your doctor, “Can you be one-hundred percent certain that I have cancer?”
She tells you that she cannot be certain without further testing and possibly exploratory surgery. She wants to refer you to an oncologist. You tell her that unless she can be one-hundred percent certain that you have cancer, you’re not going to visit the oncologist, nor are you going to submit to further tests.
Some politicians don’t want to take action on global warming because they say that scientists cannot be 100% percent certain that human activities are contributing to climate change. Yet with each new study, we come closer and closer to the conclusion that human activities are playing a part. Would any reputable scientist come out and say, with 100% certainty, that global warming is caused by human actions? No. This does not mean, however, that there is not an overwhelming amount of scientific evidence. This is just a fact of how science works. Science is not arrogant enough to assume that anything can be known with 100% accuracy. This does not mean that a scientific probability is therefore false.
Let’s look at an example. Suppose I show you a pistol. The pistol appears to be in good working order, and properly loaded. This doesn’t mean, however, that the pistol is 100% guaranteed to fire. The firing mechanism could jam. The cartridge could misfire. A meteor might strike me before I could pull the trigger. There is any number of things that could prevent the pistol from firing. Since you cannot be 100% certain that the pistol will fire, does that therefore mean you would feel safe standing in front of me while I point it at you and pull the trigger?
As more and more evidence on climate change comes in, it becomes more and more certain that human activities are playing a part. Global warming was first conceived of in 1886. Back then they only had slide rules with which to crunch numbers. The supercomputers of today use climate modeling to make increasingly accurate predictions. One of the ways that we know these supercomputers work much better than the slide rules of a century ago is that the predictions made by climate scientists become increasingly accurate over time as the process is refined. In short, while it is impossible to ever know anything with 100% certainty, climate scientists of today are rapidly approaching the 99.999% certainty mark. And the news doesn’t look good.

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