January 25, 2010


by John P. Costella

August 23, 2000 :email 0967041809

In this email we get an insight into how the politics of propaganda completely overrode the rules of good scientific practice, when it came to publications on “climate science”. Steve Schneider of the Department of Biological Sciences at Stanford University in the United States complains to a number of his international colleagues:

… please get rid of the ridiculous “inconclusive” for the 34% to 66%subjective probability range. It will convey a completely different meaning to lay persons—read decision makers—since that probability range represents medium levels of confidence, not rare events. A
phrase like “quite possible” is closer to popular lexicon, but “inconclusive” applies as well to very likely or very unlikely events and is undoubtedly going to be misinterpreted on the outside

To anyone even vaguely familiar with probability and statistics, Schneider’s suggestion is unforgiveable; and it doesn’t take a Ph.D. to understand why. Forget about climate change, for the moment, and consider the simpler example of tossing a coin. If the coin is fair, and it is tossed fairly, then the likelihood of getting “heads” is 50%. Now, imagine that you had to describe how sure you are that you would get “heads” on the next toss, to your boss—or your spouse—without using any numbers. “It’s inconclusive” would accurately convey the fact that it’s just as likely that you would not get “heads” as it is that you would. “It’s quite possible”, on the other hand, conveys the impression that it’s a possibility that is quite likely; it biases the language in one direction, without faithfully conveying equal likelihood that reality could go in the exact opposite direction.

Indeed, placing any emphasis at all on a 34% to 66% confidence interval is a complete misapplication of probability and statistics. Standard scientific practice is to only consider a result to be significant if the probability of it being true is estimated to be greater than some pre-determined threshold—typically 95%, for everyday analyses, or some more stringent threshold if the ramifications of getting it wrong are more grave.
Tom Karl, Director of the National Oceanic and Atmospheric Administration’s National Climatic Data Center, compounds the comedy:

Steve, I agree with your assessement of “inconclusive”—“quite possible” is much better and we use “possible” in the United States National Assessment. Surveys have shown that the term “possible” is interpreted in this range by the public.

Despite Karl completely agreeing with his butchering of the language, Schneider is concerned that Karl’s term is still not alarmist enough. His response reminds one of Sir Humphrey in Yes, Minister:

Great Tom, I think we are converging to much clearer meanings across various cultures here. Please get the “inconclusive” out! By the way, “possible” still has some logical issues as it is true for very large or very small probabilities in principle, but if you define it clearly it is probably OK—but “quite possible” conveys medium confidence better—but then why not use “medium confidence”, as the 3 rounds of review over the guidance paper concluded after going through exactly the kinds of discussions were having now?

Indeed, if they continued this farce for long enough, they would eventually conclude that they may as well say that it is "overwhelmingly likely"! Remember, we are here talking about a scenario that—even according to their own calculations—was just as likely to be wrong as it was right!

No comments:

Post a Comment