I have a friend who is a retired climatology professor. He pointed out that the simplest proof of global warming is that if you run all of the climate models, and exclude CO2 but include every other kind of forcing (solar, water, whatever), you get a result that’s wholly different from the observed data. But as soon as you add in CO2 to the model, then bam, it matches everything we’ve measured for hundreds of years.

If that’s true, then how can people claim that climate just changes and we can’t know why?