Um, ok... Let's recap that then.

Low CO2 levels -> Ice Age.
High CO2 level -> No ice age.

So we do know CO2 is responsible for it. We also know for a given fact that we pump a shitload of that stuff every single second of the day into the atmosphere. We also know that it keeps in the atmosphere and not "goes out into space". And although everybody would like to think that or at least like to think that the atmosphere is so big that it is not noticeable, they are so wrong that it hurts. The atmosphere itself is a tiny layer on the planet. Its a bit in the past but i think my old geography teacher made an example as to when the earth is a 1 meter diameter sphere, the atmosphere is a plasticwrap around the planet pretty much to scale.

So given there is not unlimited space in the atmosphere and we know we pump TONS of CO2 into it, you are of resolv that we are not responsible for it?

Lets take it two steps further. Yes there is CO2 in the ice. There is also methan, lots of it, and that SOB is even worse than CO2. The ocean also is full of CO2, about a thrid of what is put out, is absorbed by it, but the saturation levels are making the ocean now toxic to many creatures, food chains get killed of in very dramatic ways there. And lets not forget about the worlds largest carbon sinks: Trees. We keep burning them down like there is no tomorrow.

So we do our best to pump as much CO2 into the atmosphere as we can, which we already know for a fact, makes the planet warmer. With that ice starts melting. The melting ice releases more CO2, which in turn makes it warmer, getting more ice to melt, releasing more CO2. To make matters worse, the warm temperature dries up small rivers and lakes that usually keep a few gigantic forrests alive. Those trees and other plants, die, fall on the ground, start to rot and, yes you already guessed, start to release some more CO2.

I am not saying there is no release of CO2 elsewhere, in nature, but i am sure as hell it is us human beings who are responsible for getting the ball rolling.

What is more important though is that we try as people on this planet, to slow that ball down as much as we can, because its going ond where its going is gonna be awful either way. Unless you are going to die in the next 20 years, you will sit with the rest of us here and expierence some pretty nasty things.