Indeed, but you're ignoring all the negative feedback elements. Put it this way: if positive feedback was the only factor here, then there would have been run away warming from, lets say, volcanic activity.
Furthermore, CO2 is actively soaked up by the oceans forming calcium carbonate, that is why the level of CO2 in the atmosphere has been decreasing over the last 100 million or so years (though, this is obviously a MUCH slower process than our immediate concern, which is the next 100-200 years).
What is being argued in the scientific field is the correlation between an increase of CO2 and the increase in temperature. Using the green house model this will have a logarithmic relationship, where a lighter initial concentration of CO2 has a great slope.
The climate is very very complicated, I would go as far as to say, as complicated as a biological entity. I'm willing to bet that research on it will still be very active a hundred years from now, if we haven't destroyed ourselves until then.