I don't deny that we are destroying the world and the ecosystems, but how is CO2 responsible for the garbage in the oceans? 10'000 years ago we were living an

I don't deny that we are destroying the world and the ecosystems, but how is CO2 responsible for the garbage in the oceans? 10'000 years ago we were living an ice age. The prehistoric men didn't produce any CO2, yet our world has been warming up since then. This CO2 thing is very convenient to come up with new taxes (to steal your money!)