Wednesday, May 18

AGW is a crock

"Global warming" is one of those phrases that has a built-in ambiguity: There's no debate about the idea that the planet has warmed over the last century. In fact it's been warming for the last 330 years, since the last "Little Ice Age" around 1680.

The question is, what's the cause? It certainly *isn't* CO2, since the amount of that gas released by human activity was virtually nonexistent until around the late 1800's--but the planet had been getting warmer for a century by then.

The notion of CO2 as the cause of global warming--and specifically of human-caused GW--comes from five main observations:
  1. Since around 1960 (subject to my iffy memory--I'll try to confirm) an observatory on top of a mountain on the island of Hawaii has been measuring the amount of CO2 in the air. A plot of CO2 versus time has been increasing almost in a straight line since they started taking the measurements;
  2. We know from lab experiments that CO2 is fairly transparent to incoming energy from the sun, but substantially opaque to longer-wave heat reflected back from earth's surface. That is, it contributes to the "greenhouse effect";
  3. Earth has been warming during this period;
  4. Human-caused CO2 emissions--specifically from automobile and industrial combustion of oil, coal and natural gas--have risen sharply since around 1950.
  5. Finally, extraction of several very deep ice cores in Antarctica, covering roughly 800,000 years, seemed to show a high correlation between atmospheric CO2 and a couple of indicators ("proxies") of temperature. Ergo, CO2 must drive global temperature cycles.
This collection of observations strikes most people as highly convincing proof that humans are the cause of global warming, by means of high CO2 emissions.

Let me quickly admit that the first time I saw the CO2 plot from the Hawaiian observatory I thought "we're in deep trouble--you can't change anything in nature that much and not expect something to go seriously haywire."

But it turns out there's a lot more to the story--all of it weighing against CO2--let alone CO2 produced by human activity--having a measurable effect on GW.

Take the Antarctic ice cores, for instance: There certainly was a strong correlation between CO2 and temperature proxies--they both rose and fell at virtually the same time. But on closer inspection scientists found that that the two quantities were not exactly in-phase--and in fact, instead of temperature following changes in CO2 level, it was the other way 'round: CO2 started rising after temperature began rising.

Whoa. Wouldn't that mean.... Yes, it completely trashed the notion that CO2 caused temperature changes--at least at that location. Doesn't mean it couldn't happen elsewhere, but certainly wasn't true at that spot.

A second debunking factor is that the planet's been warming for 330 years, but humans have only been burning substantial quantities of fossil fuels since around 1930 or so (depending on your definition of "substantial"). That meant that some other factor was causing the slow warming. While CO2 might have a small effect, it certainly wasn't the main driver.

Similarly, a closer look at the effectiveness of CO2 as a greenhouse gas showed that it's a highly non-linear effect: by far the greatest heat-blocking effect occurs with the first 200 parts per million, with more CO2 producing smaller and smaller heat effects.

Oh, as to the higher CO2 levels lagging (instead of causing) temperature to rise? We've known for at least 150 years that the solubility of gas in liquids is inversely proportional to temperature. That means as temperature goes up, less gas dissolves.

Roughly three-quarters of the earth's surface is water, meaning there's an intimate contact between air and ocean. Raise the average ocean temperature by a degree or two in, say, a tenth of the ocean and that would squeeze quite a bit of CO2 out of seawater. Hard to say if that would account for a big chunk of the increase in atmospheric CO2 but it's certain a well-known effect.

So...if your kids (or grandkids) come home all teary about how teacher or Al Gore or Van Jones told ''em their parents were destroying Mother Earth and it was all the fault of capitalism or oil companies or the fact that we drive too much or...anything, show 'em this and tell 'em "AGW is a crock."

Remember, you heard it here first. Clear back in 2011.

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