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May 31, 2006

Fact and Theory and Global Warming

Fact is that there aren’t many facts. But the difference between theory and fact is crucial in science and crucial to informed citizens who need to make crucial choices – some of which are based on fact and some on scientific theory. It is a theory – not a fact – that the recently observed speed-up of global warming is caused by human activity.  There is evidence for it but not proof.  That’s why it’s a theory and not a fact.

“Theory” is not an epithet.  We often must take action based on theory because it will be too late to act if we wait – possibly forever – for facts to be available.  I think global warming is one of those cases.  But it’s still crucial that we know the difference between fact and theory.

Scientists have believed for over a hundred years that the earth has been warming since a time twelve thousand years ago when much more of its surface was covered by glaciers.  (Before that, they thought that climate, geography, and species were all in steady states since creation  - that was the scientific consensus).

Recently, there has been evidence that the rate of warming is increasing.  Quite properly, many scientists were at first skeptical of this evidence.  Scientists are supposed to be skeptical.  They asked if warming was occurring everywhere or just in the places we happen to measure.  Good question since cities cause local warming without affecting global climate significantly.  They asked whether the variability was in the normal range of climate ups and downs or represented some sort of trend.  They asked if instrumentation could have changed.  Sure, some who asked these questions might have had impure motives.  But it was right, it was important to ask the questions.

The answer SEEMS to be that there has been a significant speedup of warming over the last century with real acceleration in the last couple of decades.  Doesn’t prove that this is a trend that will persist but is part of the evidence we need when considering action.  The case for action is stronger, not weaker, because the skeptics asked their questions.

In a thoughtful comment, Reader Paul S, who identifies himself as a chemist and a technical writer, takes me to task for not embracing whole-heartedly what he calls a “consensus” on global warming:

“Yes, it is always possible that the consensus could be wrong. It could be wrong in at least three ways: It might be that anthropogenic (human-caused) global warming is a complete myth. Or it might be real, but less severe than predicted. Or it might be more severe than predicted. Of these, only the first will reward us for doing nothing, and currently it appears to be the least likely possibility.”

Actually, the consensus could be right that global warming is anthropogenic and WRONG that we can do anything about it.  We could be past the tipping point.  That’s not an excuse for not acting but a very good reason to be skeptical that we’ll get the results we expect.

There is a form of very bad logic called post hoc ergo proctor hoc – Latin for the bad assumption that if A happens before B that A must have caused B.  We don’t know that the recent rise in carbon dioxide levels caused the recent warming.  There are good theories on how this could have happened but also good evidence that increased carbon dioxide levels are a CONSEQUENCE of warming.  Melting tundra releases carbon dioxide, for example.  There are also other greenhouses gases like methane, which come from cows, trees, and many other sources.

The anthropogenic theory does NOT explain why there were apparently other periods of very rapid warming before man got his hands on fire.  The evidence for these is strong.  The evidence that those warming spurts like the current one were accompanied by high concentrations of carbon dioxide is strong.  But the existence of these other spurts proves that there are other possible causes for global warming than human activity.  Perhaps the current spurt is also caused by something we don’t know about.  Hmmm….

Scientists, like all the rest of us, are affected by peer pressure.  The scientists who were skeptical of the fact of global warming are reviled rather than praised for their helpful skepticism.  It is dangerous to an academic career to say that the causal link between human activity and global warming is theory, not fact – almost as bad as admitting to having voted for theBushAdministration.  Because we know that political correctness works on scientists as well as ordinary mortals, the apparent growing consensus on an anthropogenic cause for global warming is suspect – not necessarily wrong, just suspect.

Paul S. also says:

“You do advocate taking steps, but you seem reluctant and hesitant. In the end, I think it's like any other case of taking precautions to avoid a disaster - boarding up windows when a hurricane threatens, or setting aside supplies for an earthquake.”

I am “reluctant and hesitant.”  That’s because the steps are very expensive, could be ineffectual or even have perverse results, and because “the consensus” is a theory which has not stood the test of much time or even reputable criticism.

Actually, I’m not hesitant about some steps like a return to nuclear power, increased use of wind, and solar because I think they are good ideas anyway.  I am hesitant about many proposed ethanol solution, huge subsidies or penalties, radical conservation aka the Luddites were right, and even carbon sequestration which is a great idea if there really is too much carbon dioxide but a waste of capital and energy if there is not.

We can’t hesitate to act in some of these ways.  We also can’t lose sight of the fact that we are acting on theory, not fact.  This means that we constantly try to DISPROVE the conventional wisdom; that’s the way science works.  We keep our skepticism.  We remain ready to change our actions if they prove either unnecessary or ineffectual (or counter productive).  Things could be worse than we think.  Maybe fast global warming is irreversible for the next five centuries whether it’s our fault or not.  In that case the priority is evacuating coastal areas, not reducing carbon dioxide emissions.

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