If you believe the James Lovelock and the Gaia hypothesis, the environment is stabilised by multiple negative feedback loops. However, the feedback is limited a

If you believe the James Lovelock and the Gaia hypothesis, the environment is stabilised by multiple negative feedback loops. However, the feedback is limited and will only compensate for a certain range of inputs - if these are exceeded, the entire system could "flip" into another stable configuration. Lovelock suggests that this has already happened once on Earth; the change from an anaerobic atmosphere to the present oxygen/nitrogen atmosphere, caused by the "pollution" excreted by anaerobic lifeforms (the bacteria now mostly relegated to your intestines). It's an interesting hypothesis with a fair bit of research ("daisyworld" simulation of global temperature stabilisation via albedo effects, the methyl iodide cycle, etc.) I believe his current position is that we're all doomed and the "flip" is underway.