Disagreement is at the heart of science.

A while back, I attended a conference on asteroid impacts -- an esoteric subject, I must admit, but this column will be a wealth of information if Australia ever vanishes with a mighty whomp. Of more immediate use -- particularly for making sense of the contradictory messages we are hearing about climate change and what scientists say about it -- was an odd little experience I had at the conference.

It was a lecture about what is known as "the Tunguska event" -- an immense explosion in 1908 that smashed an estimated 60 million trees over 2,150 square kilometres.

All the textbooks say the explosion was caused by a cosmic object entering the atmosphere and exploding at high altitude. Scientists still argue about whether the object was an asteroid or comet, but that's all they argue about. Everyone agrees it was a cosmic collision.

Or so I thought. At this lecture, an astrophysicist argued that Tunguska was actually caused by a massive eruption of trapped methane gas. I'd never heard this theory before and I was floored. Here was a scientist with impressive credentials -- degrees, professorship, thick accent and superb mad-scientist hair -- arguing in numbingly technical language that what I thought was scientific fact is entirely wrong.

Afterward, I told another scientist I was surprised to hear that the nature of the Tunguska event isn't settled. He shook his head. It is settled, he said. No one buys the methane theory.

I realized later that this was an example of science working exactly as it should -- both the compellingly argued re-examination of a scientific issue, and the immediate dismissal of the new argument. Would others see it that way? Some, maybe. But many would not because many people really don't get science.

For them, scientists are white-coated priests doing arcane work in laboratories filled with Bunsen burners and bubbling test-tubes. Now and then, a scientist shouts "Eureka!" and takes his new discovery to fellow scientists, who discuss whether it is true or not. After a little time, the scientists agree.

If the verdict is good, the new truth is chiselled on a mighty stone tablet that lists all the unquestioned and unquestionable truths discovered through the ages. Collectively, these truths are Science.
[Top]

Pretty much everything about this image is false.

Start with that bit about everyone agreeing. It doesn't happen. Scientists are the most argumentative people on the planet, and I say this as an opinion writer. I know ornery.

When scientists say there is scientific agreement that something is true, they mean scientists have reached a consensus that it is true. They do not mean that scientists are unanimous that it is true. Scientists are never unanimous.

That isn't because science attracts crotchety people. It's because dispute -- skepticism, discussion, debate, argument, finger-pointing shouting matches -- is the very heart of science.

In science, there are no stone tablets. There are no unquestioned and unquestionable truths.

Scientists -- at least the good ones -- always avoid the language of absolute certainty. Instead, when they think something is true, they say things like "the evidence is strong" or "the likelihood is high." All knowledge is tentative. New evidence may come to light. Theories may have to change. Nothing is sacred, nothing is carved in stone.

You want to say the Tunguska event was caused by a methane explosion? Fine. Come to the conference and make your case.

Of course, scientists are not dispassionate creatures of pure reason. They are people and they can be as petty, political and pusillanimous as any person when confronted with a challenge to their work and careers. Haughty dismissal, nasty attacks and savage mockery are common. But so are respectful hearings of the sort given to the scientist pushing the methane- explosion theory, and that readiness to consider dissent -- along with a willingness to look at new evidence that may change old conclusions -- is what makes science special.

Last year, the national science academies of 11 leading nations -- including the Royal Society of Canada -- issued a statement on climate change. It is a perfect example of what I mean.
[Top]

"There will always be uncertainty in understanding a system as complex as the world's climate," reads the very first sentence. "However, there is now strong evidence that significant global warming is occurring. ... It is likely that most of the warming in recent decades can be attributed to human activities. This warming has already led to changes in the Earth's climate."

In recent weeks, the media have been filled with contradictory messages about climate change and what scientists think about it.

Sometimes we are told that most scientists are doubters, that only a minority thinks man-made climate change is real. More often, we hear precisely the opposite.

Who's right? The statement from the 11 science academies makes that pretty clear. And it's not the only statement of its kind. Pretty much every relevant scientific body has issued a declaration that man-made climate change is real and it's happening now. In 2004, the American Association for the Advancement of Science said there is no longer any "substantive disagreement in the scientific community."

That may be confusing. Chances are you have read interviews with scientists -- real scientists, with solid credentials -- who dispute climate change. How can they say it is settled when there are scientists who dispute it?

Simple: There are dissenters because there are always dissenters. And good for them. Some environmental groups attack all climate-change skeptics as kooks and shills for Big Oil but that's unfair and unscientific. There are kooks and shills among them, to be sure. But there are also real scientists dissenting in good faith. They deserve respect.

A scientific consensus must also be respected. Fifteen years ago, most experts and scientific organizations had doubts about climate change. The evidence just wasn't there. But it's there now. And so are the scientists.

By all the accepted standards of science, it can now be said that man-made climate change is a scientific fact.

You can contact Dan Gardner at the Ottawa Citizen.
E-mail: dgardner@thecitizen.canwest.com

Back to Columns

Home

Copyright © 2005  Dan Gardner
Website Design & Management by:  GRA Web Site Design Ottawa