This is the new right wing tactic: "We don't know what percentage is caused by humans." Actually we do. Quite precisely.
Pretty much 100% of it. (Animated graph.)
"We don't know what percentage" buffs the "skeptical" image. The patina of an intelligent lack of certainty.
Just before this, it was "I'm no scientist," which appeals to anti-intellectualism ("I'm not one of those nerds") and effects humility.
What will it be next? Let's anticipate, defang, and prevent.