The theory is that as the planet warms, the increased temperature will cause other reactions that cause further warming. Essentially, these feedbacks cause an amplification of a modest warming into an out of control disaster.
Well, that's the theory, anyway. So how does experimental evidence stack up against this theory? Not so well, actually:
You know, you'd think that if the science were so rock solid, experimental evidence supporting Global Warming would be found everywhere. Odd that so much of it isn't.
OK, so the world has warmed up a bit since 1950. This is terrible, because it means that the huge amounts of carbon stored in peat bogs will now start to be emitted into the atmosphere, which will cause more warming, which will release more peaty carbon and so on until all the Earth is a baking lifeless hell.
It must be true - it says so in New Scientist ("Peat bogs harbour carbon time bomb ... the process appears to be feeding off itself ... It's a vicious circle ... we have disturbed something critical that controls the stability of the carbon cycle in our planet"). Aaiee!
Steady on. Boffins working in Canada and Germany have looked into this properly, and they say it's a load of cobblers. Studying the decomposition of bog peat in the lab over two years, they have found that increases in temperature have no effect on peat's ability to sequester (that is, keep out of the atmosphere) its huge stores of carbon.