Actually there are ways of finding out over longer periods of time and CO2 levels track that. Perhaps they aren't being clear about weather pattern changes as deforestation can have that effect and tricky to do anything about especially as populations increase and living standards too in an add way. The main problem is said to be rain forest but there are theories about what the deforestation of europe did.
When a member of the global warming swindle people edited New Scientist. He cam up with some work some one did a while ago that suggests there is some sort of natural cycle. A bloke was into focalised beetles particularly where the gulf stream hits the UK. Species found suggested that the gulf stream turns of periodical.. Every 1,000 years or so and maybe due another.
He wasn't seen as a swindler at the time and the content of the magazine tended to be far more interesting than it is these days.Of interest - pass however this work was done.The poles have other interesting features as well. Mentioned previously and knocked down as apparently it all works it's way out and melts. Some does true but
Clues to ancient atmosphere found in bubbles trapped in Antarctic samples. Scientists announced today that a core drilled in Antarctica has yielded 2.7-million-year-old ice, an astonishing find 1.7 million years older than the previous record-holder.
Also
https://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/polar-ice-caps-0
Anyway CO2 levels are highly likely to be doing something and it does have the effect that has been mentioned. All of the water vapour in the air though causing misty horizons all of the time just about everywhere. I wonder.