Why does it matter if we caused anything? If the Earth is going to get too hot or too cold for our survival, we should try to stop it. Maybe we haven't affected the climate yet, but if we try we probably can.
It matters because it changes how we would try to stop it. If it's caused by something we're doing, we could just change what we're doing. If it's natural, then we need to find a way to alter nature. That gets into terraforming, which we really don't know how to do, and it'd probably be safer to to learn to live with the climate change rather than trying to stop it.
