Positive feedbacks are the dangerous kind. here's an Example of positive feedback: The temperature increase a little bit because of the greenhouse effect and so some polar ice melts. But polar ice is bright compared to the open sea. As result of the melting, then, the Earth is now very slightly more sunlight, so it heats some more, so it melts some more polar ice, and the process continue --perhaps to run away.
That's a positive feedback.............
Then there are negative feedback. They're homeostatic. An example: heat up the Earth a little bit by putting more carbon dioxide, say, into the atmosphere, As before, this injects more water vapor into the atmosphere, but this generates more clouds, clouds are bright; they reflect more sunlight into space, and therefore less sunlight is avail to heat the Earth. The increase in temperature eventually works a decrease in temperature. Or another possibility: put a little more carbon dioxide into the atmosphere. Plants generally like more carbon dioxide, so they grow faster, and in growing faster, they take more carbon dioxide from the air_which in turn reduces the greenhouse effect. Negative feedback are like thermostats in the global climate..........
BILLIONS&BILLIONS
CARL SAGAN
