By Dr. David Evans

Let’s break down the case for human-caused global warming logically:

1) There is plenty of evidence that global warming has been occurring recently.
2) There is ample evidence that carbon emissions causes warming and that the level of atmospheric carbon dioxide is increasing.
3) But there is no evidence that carbon dioxide emissions are the main cause of the recent global warming.

The alarmists focus you entirely on the first two points, to distract you from the third. The public is increasingly aware of this misdirection. Yes, every emitted molecule of carbon dioxide (CO2) causes some warming - but the crucial question is how much warming do the CO2 emissions cause? If atmospheric CO2 levels doubled, would temperatures rise by 0.1, 1.0, or by 10.0C?

We go through the usual “evidence” offered by alarmists, and show that in each case either it:

• Is not evidence about what causes global warming. Proof that global warming occurred is not proof that CO2 was mainly responsible.
• Is not empirical evidence; that is, it is not independent of theory. In particular models are theory, not evidence.
• Says nothing about how much the temperature would rise for a given rise in CO2 levels.

Despite spending $50bn over the last 20 years looking for evidence of point (3) above, the alarmists have found none. In two instances they expected to find it, but in both cases they found only evidence of the opposite - and they have kept awfully quiet about those cases. If they just had some evidence of (3) they could just tell us what it was and end the debate.

We note that there used to be some supporting evidence, but better data later reversed that evidence. Instead there are now at least three independent pieces of evidence that the temperature rises predicted by the IPCC due to carbon dioxide emissions are exaggerated by a factor of between 2 and 10, primarily due to the assumption of overly positive water vapor feedback in the climate models. Finally, we discuss some examples of what would constitute evidence. The evidence must of course be empirical, meaning that it is independent of theory.

Typical Evidence
Typical Alarmist Offerings of “Evidence”: Polar Bears, Glaciers, Arctic Melt, Antarctic Ice Shelves, Storms, Droughts, Fires, Malaria, Snow Melt on Mt Kilimanjaro, Rising Sea Levels, Ocean Warming, Urban Heat Island Effect. Although each of these issues may say something about whether or not global warming is or was occurring, none of them say anything about the causes of global warming. It would make no difference to these issues if the recent global warming was caused by CO2 or by aliens heating the planet with ray guns.

The IPCC Said So

So what is their evidence? Chapter 9 of their latest Assessment Report 4 (2007), “Understanding and Attributing Climate Change”, contains no evidence. That CO2 is the main cause of the recent global warming is an assumption in much of what they say, and they find many ingenious ways of saying it and implying it using complex language. But repetition is not proof, and nowhere do they present any actual evidence. If you doubt me, read it yourself then say what the evidence is in your own words.

Often the assumption takes the form that nearly all the temperature rises since the start of industrialization are due to CO2 rises, or that there are no other possible significant causes of global warming.

Computer Models are Evidence
Computer models consist solely of a large number of calculations that, individually, you could do on a hand-held calculator. So models are theoretical, and cannot form part of any evidence.

Computer Models Incorporate a Lot of Sound Empirical Science
Yes they do. The climate models contain some well-established science that has been verified by empirical observations. But they also contain a myriad of:
• implicit and explicit assumptions
• omissions
• guesses
• gross approximations.
A single mistake in any one of these can invalidate the climate models. Typical engineering models that mimic reality closely contain no untested assumptions, material omissions, guesses, or gross approximations. They are the result of mature understanding of the reality being modelled, and have been tested ad nauseum in a wide range of circumstances. On the other hand, climate science is in its infancy, individual models routinely fail most tests, the climate models are riddled with untested assumptions and guesses, they approximate the atmosphere with cells a hundred kilometres square and hundreds of meters high, and they do not even attempt to model individual cloud formations or any feature smaller than the cell size. Don’t let the word “model” fool you into thinking climate models are better than they are.

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