Good, accessible, explanation of global warming

I just ran across the best, most accessible explanation of global warming I have yet to read. In particular, it addresses two common misconceptions that global warming deniers keep harping on, a) that water vapor is a bigger contributor to global warming than carbon dioxide (so why worry about carbon dioxide?) and b) carbon dioxide is such a small fraction of the molecules that make up the atmosphere (so how can carbon dioxide be having such a large effect?).

Art Hobson’s essay makes the point that water and CO2 are the two major contributors to global warming despite the fact that together they make up less than one percent of our atmosphere. The major components of the atmosphere (nitrogen and oxygen) play no role in the so-called “greenhouse effect.” Second, the key difference between water and carbon dioxide is that when water vapor levels get high, water condenses to form rain, and so the water vapor is removed from the atmosphere. This does not happen with carbon dioxide, so it is the level of carbon dioxide that controls global warming, despite carbon dioxide making up such a small portion of the atmosphere overall.

I will say that the essay is not entirely free of misleading language, in that the essay seems to imply that the levels of water and carbon dioxide are not too different. In fact, the water vapor content of the atmosphere is a few percent, while the carbon dioxide content of the atmosphere is 0.038 percent. So water vapor molecules are 100 times more numerous in the atmosphere than molecules of carbon dioxide. Therefore, the importance of carbon dioxide levels to global warming is still pretty surprising at first glance.

Art Hobson’s essay is not much longer than a letter to the editor, but it does a good job of getting at the heart of global warming. I recommend it to anyone.

Tim

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