I don't confirm nor deny because I can't prove either way. Atmospheric CO2 & CH4 are rising and that's a provable fact. Everything that comes after that is postulation. We're heading into uncharted territory with only theory to shine a potential path.
I don't think it is all that important to know how much effect our man-made greenhouse gases have. It's a fairly minor blip compared to other forces on long time scales, and we are going to quit burning fossil fuels at some time in the not too distant future. I think it is good to realize first that
we are currently in a major ICE AGE. We just happen to be in a warm inter-glacial period within that ice age. Normal earth temperature was ~20F warmer 100 million years ago than it is in our current period.
You know that cold spell 25k years ago where much of the northern hemisphere was covered by an ice sheet several thousand feet thick? That is more the norm than the exception. And we are due for another cold spell.
I mean
check out that ice sheet! That is expected to return in the not too distant future (within a couple thousand years) if we do nothing. Granted, these greenhouse gases may have undesirable effects in the shorter term, but honestly no one really knows if it will be a net negative or positive. Many coastal areas will have issues with rising oceans, but large expanses of land in high latitudes will become arable and livable. Total earth rainfall should increase. The problem is that we don't understand what is effecting the climate well enough to predict what effect our actions will have.
At any rate, we *will* want to do something to prevent the next glaciation. Doing stuff to make the earth a little warmer now does not seem to be a big problem in light of that.