Thursday, February 15, 2007
Global Warming and Red Herrings
Two arguments are often made by skeptics of climate change. The first is that the link between human activities and global warming is not definite. The second is that while "climate alarmists" claim that a consensus exists among scientists on this issue, there is no such thing as consensus in science.
Both arguments are red herrings.
Skeptics who say that the link between climate change and human activities "isn't definite" are throwing up a red herring because the statement distracts from what they really mean: Despite the very strong body of evidence favoring a link between human activities and significant climate change, they do not favor action for other reasons — usually economic reasons. Policy action never requires certainty. So folks who raise this argument should be asked why they demand certainty with climate change.
The answer, of course, is that they want to ensure inaction.
Science never proves hypotheses and theories with 100 percent certainty. From the perspective of logic, it is impossible to rule out every possibility, because we have not conducted every conceivable observation or experiment, and we haven't lived in the future. It is always possible that we haven't thought of something. So we can only test the predictions arising from theories. And as the philosopher of science Karl Popper pointed out, if the predictions hold up with repeated testing, then the best you can say is that the theory has been well "corroborated."
I like that word and I try to use it when I can in my science stories.
So folks in the petroleum industry who make the lack of certainty argument are technically right. The link isn't, quote — definite — endquote. It never will be. But it is very well corroborated that human activities are causing significant changes to the climate.
When they say it to us, we might ask them whether they think the predictions made by their corporate economists are "definite," or whether their calculations of petroleum reserves are "definite." They would have to answer "no." And then we could ask whether their companies should not drill for oil in a promising spot because the predictions that oil is there are not "definite."
The "no consensus on climate change" red herring is just as distracting. Once again, policy can proceed without consensus on the underlying scientific issues. We might just decide that action is warranted as a kind of insurance policy — just in case the scientific projections are right. Speaking now as a citizen, not a journalist, I would say that we should have taken that approach long ago, before the current consensus emerged. If we had, we would be in a much better position both geopolitically and environmentally.
In this case, of course, a consensus really does exist. "Consensus" means "general agreement." And the word "general" means "affecting or concerning most people." I think it is completely accurate to say that most scientists who study one aspect of climate change or another and who publish in peer reviewed journals agree on some of the fundamental aspects of climate change, but by no means all aspects.
There is simply no question that most such scientists would agree that humans are very likely responsible for most of the observed warming over the past 50 years, and that potentially disruptive changes are likely to continue. This is one of the conclusions of the Intergovernmental Panel on Climate Change.
But if the word "consensus" bothers you, call it a "general agreement." Or forget trying to affix a one- or two-word label and be punctiliously precise like Libby Rosenthal and Andy Revkin did in their story for the N.Y. Times on the day of the IPCC release. They referred to the conclusion from "the leading international network of climate change scientists."
Global warming is a huge and complex subject with many unknowns. For example, will it snow more or less here in Colorado? Some of the predictions are for more snow and some are for less, and the science is uncertain. What about sea level? How fast will it rise and how high? The IPCC was pretty conservative there, backing off some of the scary scenarios floated last year about 20 feet of rise by the year 2100. But those scary scenarios are still credible. You can say with utter accuracy that paleoclimate records demonstrate the following: The last time the Arctic was as warm as computer models say it will be by the year 2100, sea level was indeed 20 feet higher.
Should we be worried? Stepping out of my role as a journalist again, I'll say unequivocally: I think so. But there's no consensus on this question. And maybe that's the problem.