Evidence-free Zone, Indeed

When I went to Alaska and Minnesota this summer, one of the (many) things that struck me was how hot the weather was--mid to upper 80s in Alaska, mid 90s (heat index close to 100) in Minnesota. I hoped that, at least, was something I could leave in Georgia for a few weeks out of the summer. I was wrong.

Then I thought, "I bet someone's gonna use this to talk about global warming and environmental legistlation." Well, here it is! Some senators (including McCain and Hillary) went to Alaska and Canada to talk to people about how hot it has been. (I'm guessing that was the reason for the trip.) So far, so good. But the thing that troubled me about the article was that these pieces of personal testimony were treated as some kind of evidence or confirmation for global warming (treated so at least by McCain, if no one else). Here are some tidbits from the article (emphasis mine):

Anyone doubting the effects of human activity on global climate change should talk to the people it affects in Alaska and the Yukon, U.S. Sen. John McCain said Wednesday. Fresh from a trip to Barrow, America's northernmost city, McCain said anecdotes from Alaskans and residents of the Yukon Territory confirm scientific evidence of global warming.

McCain said the trip has been valuable for the accumulation of evidence that can be used to push the bill.

Personal testimonies do no such thing. They do not establish the truth of claims, provide evidence for claims, or even confirm evidence for claims. What could they possibly add to analyses of trends in temperature over the course of years, decades, and centuries? Nothing. What could stories about how hot people think it is tell us about global warming? Nothing.

Personal testimonies do not belong in such debates. They belong on late night TV infomercials--and even then they don't actually provide evidence for anything. They only tell you that such-and-such diet pill worked for so-and-so. They tell you that this person lost weight with that exercise machine. That's it. Period.

One of the strengths of personal testimonies is that they provide actual, real (hopefully) examples of something that a "scientific" study might show. But they are just that--examples. Illustrations. Not evidence or confirmation (unless by "confirms" one means "backs up" or "corroberates," a much weaker relationship than one of evidential confirmation with which the article seems to be concerned). This is a strength because the testimonies, if true, cannot be denied. There is no denying that people in Alaska are hot, that the spruce beetle is wreaking its havoc upon the blue spruce all over the state, that people report erosion due to higher than usual melting, etc. Testimonies tend to stick with us and so act as a great persuasion in favor of a claim being made. We have more of a tendency to accept the claim. But persuasion is not evidence. We can be, and too often are, persuaded by bad arguments. The truth of the causal claim that human activity (driving SUVs, spraying CFCs into the atmosphere, etc.) has a damaging effect on global climate change is in no way affected by what Mrs. Smith says about her dried up gardenias. Causal claims are justified by much different standards.

"If you can go to the Native people and listen to their stories and walk away with any doubt that something's going on, I just think you're not listening," [McCain] said.

Opponents who ignore evidence of humans contributing to climate change, Clinton said, are participating in a trend of turning Washington, D.C. into what she calls an "evidence-free zone."

This is exactly the kind of rhetoric that puts the debate in a context where it doesn't belong. Putting the onus of the discussion on personal testimonies, as sad and pity-inspiring as they are, takes one out of the context of the sort of evidence that is needed and into the context of ideological persuasion.

Now, lest I be taken as uncharitable, it is true that the article mentioned the "overwhelming scientific evidence" for the causal claim that human activity is affecting global climate change. But such statements should be the focus (especially when we're talking about the basis for changing legislation) and should be squarely separated from the anecdotal "evidence" that is at the heart of the piece.

"You just keep saying something no matter how untrue and unfactual it might be, over and over and over again, and try to drive the politics to meet your ideological or commercial agenda," [Clinton] said. "That is a grave disservice to our country."

Indeed it is, Senator Clinton. Indeed it is.