When someone tells you they are about to expose a swindle, you'd expect them to tell you in what it is the swindle consists. In the case of human-activity-induced global warming, you might expect them to explain the theory behind the alleged looming human-caused disaster.

This, however, the Channel 4 Swindle documentary makers entirely fail to do. Instead, they tell you what Al Gore said in his absurd movie "An Inconvenient Truth".

In particular, they have Al Gore pointing to the similarity in the pattern of variation in atmospheric carbon dioxide concentration and in global mean temperature over the last 650,000 years, from which the audience (Al Gore's audience, that is) is supposed to infer that carbon dioxide concentration controls temperature. (Interestingly, perhaps, the YouTube clip from Gore's "Truth" movie that we linked to in an earlier post has now been pulled.)

Channel 4's Swindle team correctly point out that changes in atmospheric carbon dioxide have generally followed, not led, temperature changes: the lage being about 800 years. That means that if there is a cause and effect relationship it must be the opposite of the one Al Gore suggests.

So the Channel 4 production effectively debunks Al Gore, and at the same time leaves the viewer to believe that Al Gore's presentation is all there is to climate change science. A piece of misdirection at least as pernicious as Gores's.

It is not my intention to remedy the deficiency in Channel 4's documentary by providing a disquisition on the postulated role of carbon dioxide in climate change, but it needs to be pointed out that there is a vast difference between, on the one hand, saying that a small natural changes in atmospheric carbon dioxide concentration did not, in the past, drive the major observed changes in global mean temperature, and on the other hand, saying that an abrupt artificial doubling in atmospheric carbon dioxide due to fossil fuel combustion will have no effect on global climate.

In fact, everyone seen in the Swindle documentary, Richard Lindzen and Dr. Wunsch of MIT, the people from NASA, and even, with a little persuasion, the Eeore-like Nigel Calder, the one-time editor of pop-sci mag, The New Scientist, would agree that doubling atmospheric carbon dioxide concentration will, all other things being equal, raise global temperature by a small but significant amount.

The real scientific argument, as we have discussed elsewhere, is about all other things that will not be equal. And sorting that out is an interesting and challenging scientific question. So if you want to know what the theory of human-induced climate change is all about, be warned: you'll learn nothing from C4's production.

But the Swindle documentary not only misinforms about what it claims to debunk, it makes the absurd claim that the theory of human-induced climate warming is preventing development in poor countries. As evidence, they show an African mother, with a child strapped to her back, cooking in a hut over an open fire. Such smoke exposure, C4 tells us, kills millions of women and children, and is one of the evil consequences of denying Africans coal-fired electricity generating stations.

This is total bunk. I was raised in a house without electricity. Until just over 100 years ago the entire human race was raised without electricity. What those of us in the more developed world had, until recently, was not electricity but chimneys. Yeah, those concerned about Africans breathing too much smoke should introduce them to the technology of the stove pipe.

If later on, they want air conditioning and TV, then by all means let them burn coal. There's nothing to stop them except their own poverty and the Swindle team have nothing to say about alleviating that.

There is one other thing the Swindle team failed to mention. While asserting that carbon dioxide comprises a tiny, practically negligible, fraction of the atmosphere, they neglect to mention the impact that doubling the concentration will have on the biosphere quite independently of any climatic effect. Here's how it works.

Plants absorb carbon dioxide from the atmosphere and produce sugar and every other organic tissue constituent from it. Carbon dioxide enters the tissues of a plant by diffusion. But if there is a path for carbon dioxide to diffuse into the tissue, there must be a path for water vapor to diffuse out of the tissue.

What that means is that plants exchange water extracted from the soil for carbon from the atmosphere. But the supply of water available to most plants is limited. When that supply is used up, plants simply close the diffusion channel by which water and carbon are exchanged and photosynthesis comes to a halt. That means plant production is water-limited.

Now consider what happens if you double the atmospheric concentration of carbon dioxide. Carbon dioxide will diffuse into the tissues of a plant more quickly because there is now a steeper concentration gradient (photosynthesis in the leaf removes carbon dioxide causing the tissue carbon dioxide concentration to approach zero). And if carbon dioxide diffuses into the tissue faster, that improves the rate at which plants exchange water for carbon dioxide. In other words, if plant production is water-limited, it is equally carbon dioxide limited.

So if you double the atmospheric carbon dioxide concentration you will more or less double plant production on all but most well-watered soils. Greater plant productivity means greater crop yields, greater crop yields mean more people. Ready for a 12-billion-person planet? Personally, I incline to a more-the-merrier view, but how about you?

That won't be all of it. Species composition of forests and other ecosystems will change as some species take advantage of the increased carbon dioxide concentration more effectively than others. Changing the composition of plant communities will likely mean mass extinctions of organisms dependent on existing plant communities.

So anyone who tells you that doubling the concentration of carbon dioxide in the atmosphere is unimportant, is almost certainly wrong and if that's what you're being told by a well-endowed broadcaster, I'd say you have been targeted as the victim of a swindle.

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