By Brian
Here's evidence of a positive feedback problem, something that's pretty common scientific vernacular, but has--thanks to bloggers like Kevin--begun to merge into popular discourse.
Elizabeth Kolbert's forthcoming book, Field Notes from a Catastrophe, frames the problem in exquisite detail. The idea will be intuitive to anybody who--because it's their favorite shirt, and it just fits so well--has made the mistake of wearing black clothing in the desert and so, to avoid the discomfort of being a heat sink, has changed to something white. The dark stuff makes you hot and the white stuff leaves you (relatively) cool.
Well, ocean water, because it's pretty dark, absorbs a significant amount of heat, which increases the surface temperature of the earth. A warming earth surface, though, means that glacier ice--even though it's remarkably effective at reflecting incoming sunlight--will melt, fast. And when glaciers melt and recede, they expose more dark ocean to the sun, speeding up the process until the glacier has disappeared altogether and can no longer act as a defensive mirror.
Unfortunately, the parallel phenomena that cause global warming are littered with positive feedback mechanisms (melting permafrost, for instance, exposes pockets of long-contained greenhouse-gas bubbles, which, once released, contribute futher to the heating process, melting more permafrost and on and on we go). Which means that, now that the warming has started, cutting emissions just might not be enough at this point to keep us safely cool.
UPDATE: A sassy li'l commenter pointed out a bit of unfortunately unclear language. The paragraph about glacier ice has been changed accordingly.
