Sunday, October 11, 2009

Climate quackery

I just stumbled across this from the BBC: "[In 2007] the IPCC's Fourth Assessment Report concludes it is more than 90% likely that humanity's emissions of greenhouse gases are responsible for modern-day climate change."

Pretty damning, huh? Except it isn't. ">90% likely" is another way of saying "<10% that this could happen by random chance" or, as it's often shown in scientific papers, "p < 0.1". Or, rather, that's how it might be shown in scientific papers if they were published with such loose bounds - but they're not. The publication standard for most reputable journals is 5% significance. My supervisor once described it thusly: "if you haven't proven it to 5% significance, you haven't proven it". And with good reason - no journal's reputation could survive long if it published, on average, one incorrect study each issue.

One- and two-sigma errors crop up all the time. In a moderately-sized physics class, you would expect one student to get a result two standard deviations from the mean, not through incompetence but through random errors. With a "science" as complex, fuzzy and politicised as climatology, p<0.1 is a null result.

The BBC also has this graph of atmospheric CO2 readings from Mauna Loa from 1958 to date:

Here's my rather less scary one from the same data:

Note that the population of the world reached 3 billion in 1960 and 6 billion in 1999, so the atmospheric CO2 per person is down over 40% in that time! Hardly convincing, prima facie, that people are the problem.

Then, of course, we have this BBC piece telling us that the hottest year on record was 1998 and that temperatures have been stable for the last decade - and will quite possibly decline over the next 20-30 years. I'll not mock the secret models which have utterly failed to predict any of this, but suffice to say that if you put garbage in, you get garbage out, and it's not a good idea to set policy based on garbage.

So, yeah, "global warming" (or "climate change" as people prefer to call it now that it's not actually getting warmer) is very much unproven. And yet... we're forced into using mercury-filled lightbulbs, taxed through the nose for petrol and flights, "encouraged" to use renewable energy sources as our politicians argue over whose hair-shirt is hairier and who can cut emissions the most.

History will judge harshly the current mass-hysteria over climate: "they actually thought they were saving the world"

- KoW

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