Stardate 20011227.1558

(On Screen): This article discusses the fact that there's a "low" probability of the West Antarctic Ice Sheet melting: "only" one chance in 20 over the next two hundred years. Were that to happen the result might be a 5 meter rise in world ocean levels, but not to worry! It would happen slowly and could be reacted to.

It misses a different scenario which has been proposed: that the WAIS might detach and slide out into the sea over a period of a couple of days. (Cores have shown that the whole thing is sitting on a layer of slush.) It might take years for the resulting icebergs to melt, if they did, but the effect on world ocean levels would be very rapid; it would propagate around the world in no more than a couple of weeks. (There'd be time to evacuate, but nowhere near enough time to build the necessary dikes.)

But then the article talks about it melting, and that's not a foregone conclusion. There's a different possibility. If it were to slide off into the sea, it would break up into millions of icebergs with a surface area far greater than the WAIS has now, and they'd all be white. That would raise the average albedo of the earth, reflect more sunlight back into space, and cause a general cooling. This would cause more snowfall, increase in the size of glaciers and snowpacks all over the world, further increasing albedo, and perhaps create a self-sustaining cycle leading to a new ice age in a few hundred years.

This is, in fact, one of the theories about how ice ages happen. And in fact, there's strong evidence that the WAIS did vanish completely during the last interglacial period. Did it set off the next ice age when it did so?

So what could we do about it if it were to happen? About the rise in ocean level, absolutely nothing. About the onset of a new ice age? Well, um, err, (ahem), how to put this? We could release lots of greenhouse gases.