William M. Briggs, Statistician

Reuters’s, on 3 January, had this headline, “2008 to be in top 10 warmest years say forecasters.”

A quote:

2008 will be slightly cooler than recent years globally but will still be among the top 10 warmest years on record since 1850 and should not be seen as a sign global warming was on the wane, British forecasters said.

Where to start? First, the anemic forecast. Suppose the global mean temperature is, as predicted by several models, increasing, though this increase is subject to fluctuation from year to year, such that for one or two years the temperature might actually decrease, but in the long run, the temperature will still increase. Call this scenario the increasing temperature climate. It is important to emphasize that the increasing climate schema is consistent with both a significant man-made component and with the change being due to external causes. Now suppose, as has also been proposed, that the global mean temperature instead followed this cartoon, depicting a cyclically-changing climate:

This cartoon (and those based on other potential climate scenarios) is also consistent with either man-made climate changes or with the changes being due to external causes. It is just that, in this picture, the man-made component is harder to quantify. This is because of the trivial truth that man must influence the climate (see this), and that this influence will either be trivial or significant.

So it is a tautology to say that either man-made global warming is significant or it is not. One of those conditions must be true. It is also observed that the global mean temperature is correlated from year to year, so it is a fact that the temperature is somewhat constrained, in the sense that we will see little change from year to year, no matter whether mad-made global warming is significant or not, and regardless whether a general increasing or a cyclic climate holds.

Lastly, it is also the case that the global mean temperature has been increasing since the late 1990s until 2006. In 2007, the temperature decreased.

So the prediction that “2008 will be in the 10 ten warmest years” has an overwhelming probability of being true regardless whether man-made global warming is significant or not, and regardless whether an increasing or cyclic climate holds. That is, no matter what, this prediction is probably true, and it is useless as its intent was to give indirect evidence that the increasing climate scenario holds and that the man-made component of global warming is significant. It does neither such thing. Presenting this prediction as news is a clever debating tactic, but it is misleading, because the alternatives are not presented, even though the forecast is just as much evidence for them.

“‘The fact that 2008 is forecast to be cooler than any of the last seven years does not mean that global warming has gone away,’ said Phil Jones, director of climate research at UEA.” Jones is right, partially. But he forgot to say, “That fact the 2008 is forecast to be cooler than any of the last seven years also means that it might true that the climate is cyclic and that man has no real influence on it.”

This forecast is not additional evidence that an increasing climate or that man-made global warming holds.

Some guy named Joel Connelly at the Seattle Post-Intelligencer has written another one of those “We must do something now” global warming articles. What makes his piece distinct is that he compares those who express honest skepticism in global warming claims with those who deny the holocaust.

This sort of thing is exceedingly moronic, yes, but it is one more empirical observation that shows Godwin’s Law continues to hold. That law states:

As an online discussion grows longer, the probability of a comparison involving Nazis or Hitler approaches one.

And let’s not forget that exquisite corollary of Godwin’s Law, Benford’s Law of Controversy:

Passion is inversely proportional to the amount of information available.

Connelly’s piece follows Benford’s Law, too, because of the one thing that I find happening with increasing frequency. Here’s a quote:

Nobody is certain what will happen.

So far, however, change has proceeded at a faster pace than even pessimistic scientists predicted a few years ago.

Who could have forecast a 2-degree rise in Antarctica’s temperature in just 35 years? Nobody forecast the breaking off of giant Antarctic ice shelves. The rapid shrinking of the Arctic ice pack has surprised researchers…

Nobody is “certain what will happen”, except Connelly of course, because he then uses the empirical fact that scientists with their best models have failed to predict actual observations to argue that we should believe those scientists’ models and that “we must act quickly, within a decade.”

My friends, the opposite is true. If scientists are failing to predict actual observations, then we should have increased skepticism that what those scientists are saying will actually come to pass. At the very least, we should increase the error bounds, the “plus or minuses”, that accompany their predictions.

It also does not follow that because the model error is negative, i.e. that more warming took place than was predicted, that the situation is even worse than we thought, and that even faster warming rates will occur. This argument is a logical fallacy unless it is conjoined with the additional premiss that “warming must occur, and that if our predictions show that less warming will occur than actually does happen, then even greater warming will take place.” But if you assume that premiss, then your argument is circular, and therefore useless.

Failed predictions should not lead to increased passionate belief in those predictions.