December 8, 2009

Briggs: ‘The Copenhagen Diagnosis’ Fails Logic 101

The new IPCC report, a briefing for the Copenhagen attendees, fails to understand that a rise in temps does not constitute proof that man caused it.

FROM-Pajama Media

William Briggs

Our leaders have gathered in Copenhagen. There, in their winter of discontent, they pledge to do something about climate change.

Before everybody arrived, to make sure those leaders were briefed, they were given a document outlining the evidence for man-made global warming (a.k.a. climate change, or AGW). This is “The Copenhagen Diagnosis.”Stephen It’s-Getting-Cold-No-Wait!-Hot-Out Schneider and many other environmental persons took up pen to detail the best — or at least, most frightening — arguments for action. It is thus important to understand this document to discover whether the information offered is convincing … or even relevant.

The main evidence is contained in several bullets of the executive summary (readers are encouraged to download the document and follow along):

Surging greenhouse gas emissions: A picture is shown of CO2 and CH4 increasing (fig. 2) since 1980. But showing these gases are increasing in not proof that AGW is valid. AGW theory states that increasing gases cause dangerous warming. Therefore, what is needed, and what is lacking, is a demonstration that the causal link between the two — warming and increased gases — has been proven.

Recent global temperatures demonstrate human-induced warming:
They claim that the small amount of observed warming before the last decade is “consistent” with AGW. This is true. But there are many other theories of climate change; AGW is just one of them. The observed changes in temperature are consistent with many theories, not only AGW. And what of the last ten years of no change, or even cooling? It is dismissed as a “short-term fluctuation,” which is “usual.” The problem is that this “fluctuation” was not predicted by AGW models; this weakens our belief that AGW is correct.

Acceleration of melting of ice sheets, glaciers and ice caps: Even if this were true — and it is not so in recent years — it is not evidence that AGW is true. It is only validation that ice melts when it gets hot. Remember, we are after proof that the AGW theory is true. An observation of what happens when it is hot outside is not acceptable proof. We want to know what caused the air to get hot, not what caused ice to melt once it was hot.

Rapid Arctic sea ice decline: This merely repeats the previous point, and is also not valid evidence for AGW, particularly in light of that decadal cooling “fluctuation” we are experiencing.

Current sea level rise underestimated: When that ice melted, the water went into the sea (where else?), and so this point is again not evidence of AGW.

Sea level predictions revised: They must have had room left over for them to repeat the same point a fourth time. There is no other explanation for why they insert this non sequitur once more. Let us repeat: observations of what happens to something when the air is hot are not evidence that mankind causes global warming.

Delay in action risks irreversible damage: This is the most common — and most irresponsible — method of argument. It says bad things will happen if AGW is true. But it is logically impossible that what might happen could be proof for AGW. This is a scare tactic, a logical fallacy so blatant that we can only hope the “Diagnosis” authors blushed when they wrote it.

The turning point must come soon: Alas, this last point assures us that they did not blush, but were willing to commit the same fallacy again, and with gusto. Threats of doom are simply not proof of anything except excitability in the their authors.

So much for the summary. What can we learn from the document itself?

Skeptics will be pleased that critical studies of proxy reconstructions are cited (Soon & Baliunas and McIntyre & McKitrick), but they’re there only to show how open-minded the “Diagnosis” authors can be. For no sooner do they admit these criticisms, then do they immediately claim that these papers “have been rejected in subsequent work.”

Rejected is not, of course, the same as refuted, but who would notice a nice logical point like that?

But even if these criticisms were refuted, the subsequent “hockey sticks” and other pictures of historical changes in temperatures are not direct proof for AGW’s validity. The “Diagnosis” authors, it is obvious, do not understand this. They feel that because it might have been colder in the past, and warmer now, that this proves AGW. It simply does not.

Those observations are consistent with many theories of climate change, AGW being just one of them. What would be proof, and what is missing from the “Diagnosis,” is evidence that the AGW models have skillfully predicted future temperatures.

They have not done so.

In fact, to disguise the AGW models’ poor performance, they employ statistical slight of hand: every picture of temperature leaves out the last few years of cooling. This is because AGW models said it would grow hot, but we actually cooled.

The models, in other words, were wrong.

Lest our dear leaders notice this and become confused, the “Diagnosis” authors resort to the oldest logical fallacy. They simply assert: “We are smart people, therefore AGW is true.”

Unfortunately, and since people are so willing to believe, that might be all the proof that is needed.


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