Can you provide an argument against CO2 being the main cause of Global Warming?

So most documentaries, scientists and whatnot always give information about how CO2 is the main reason for global warming seeing that it causes the greenhouse effect and all. Let’s see if we flutherites can provide a detailed argument against this. Surely there are other reasons for Global Warming. A detailed scientific argument would be appreciated. You can include examples, quotes, causes. We have to win our imaginary opponents. Please don’t give responses about how CO2 is the main cause as this post is against the fact that CO2 is the main cause for Global Warming.
If you think that it is the main reason, would you be able to temporarily change your opinion and argue with yourself? Challenge.