This is an argument over the change in atmospheric CO2 from 0.03 to 0.04%. The value 0.04% is the same as that of water vapour, another greenhouse gas. Does such a change really have impact suggested?
Much of the time PROXIES are used to construct paleo data. This has its own inherent problems when it comes to extrapolation. The IPCC and MSM may claim the science is settled, I am still sceptical

https://www.sciencedirect.com/topics/earth-and-planetary-sciences/paleotemperature

You should also ask why "Global Warming" morphed to "climate change".
Climate has always changed, the evidence is irrefutable.