Lots of Climate Science Deniers deny the radiative forcing effects of CO2 or the magnitude thereof.
The WHY of CO2 radiative forcing is not even an issue. It was measured by Tyndall in 1850-something so we know it exists. And we know the physics and chemistry of WHY it happens. You can't seriously be questioning molecular vibration in 2020, can you? https://en.wikipedia.org/wiki/Molecular_vibration
So are you questioning WHY CO2 in the atmosphere has suddenly increased to a level not seen in millions of years? Might have something to do with the trillions of tons we have released form FF combustion?
We know WHY CO2 is in the atmosphere. We know WHY it absorbs and radiates IR energy. We know WHY that heats the planet. Exactly what part of the long-established science are you questioning?