Generally causation and correlation can only be distinguished by running experiments. Given that we only have 1 earth climate, long time needed to gather reliable results, and the quite apparent correlation, which experiment would you like to run for next 50 years, slow down co2 output to see if climate warming slows down, or continue increasing co2 output, and see where that leads?

Infact, increasing co2 output would be kind of boring experiment, we've tried that already.