kent_allard_jr: (morans)
[personal profile] kent_allard_jr
My old thesis adviser Andrew Gelman writes about climate trends today. He notes that it's really hard to predict future trends from past values, something you learn in intermediate stat classes (which is as far as I ever got, sadly) and worth reminding ourselves from time to time. Accurate predictions need a strong model, one consistent with the data but derived independently from it.

Do climate scientists have strong models? Well I only know stuff from Traveller and planet-building guidebooks for science-fiction writers, so I'm no kind of expert, but what little I learned suggests that dumping methane and CO2 into the atmosphere will, all else being equal, make the planet hotter. Are levels of these greenhouse gasses higher than they used to be? From what I've heard, yes.

Naturally, all else is not equal, and there are both negative and positive feedback loops. For example, higher temperatures can lead to more evaporation. That means more water vapor -- which as a greenhouse gas, increases temperature -- but also more cloud cover, which raises the albedo and cools the planet down. These complications, I suspect, add variability to the models and make predictions harder. Climate-change denialists may find that comforting, but not me: I'm not happy that we may end up in an ice age, or we might turn Earth into Venus, but Earth normal is somewhere in the middle so it's all OK. I'd rather take steps to ensure the climate doesn't oscillate out of control.

What's more, the denialists use rhetoric that makes them hard to take seriously. Global warming isn't a "fraud," and anyone who says so is a hack or a nut. Skepticism is called for, particularly with predictions and trends, but that kind of talk has no place.
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August 2012

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