Carl Sagan mentioned another theory on
albedo, in which the increase in
inclement weather caused by
global warming increases the cloud cover naturally, acting as
negative feedback for free. The drawback, of course, is that we may be stuck with the
bad weather.
And we can't really depend on this, since it's still just a theory. A competing theory is that the melting of the polar ice caps due to the greenhouse effect will act as a positive feedback, and accellerate global warming, since we'll be both decreasing the amount of white reflective surface on the earth and increasing the amount of hydrocarbons in the atmosphere (there are many trapped in the ice).