So let me be clear
CO2 is increasing, that is measured and I can verify that by a simple common sense test, (we burn petroleum which is trapped carbon, that is not being replaced faster than we make it, ergo we're adding to CO2 by using petroleum).
Trees make petroleum given enough time, hence they must be slightly carbon negative as is anything else that goes into making petroleum. So nature traps carbon without us, (in petroleum, coal, peat, Kerogen, shale tar, etc. everything else we are using up faster than it is produced).
CO2 traps infra red emitted from earth and re-emits in all directions, i.e. half of it is sent right back to earth. That's more difficult, I can verify that with H2O because cloudy nights hold in the warmth, so I've experienced the H2O effect.
But the CO2 effect I can't see. So lets get an absorption spectrum to check it, yep CO2 does absorb infrared:
http://hosting.soonet.ca/eliris/remotesensing/bl130lec3.html
Next up, does it also absorb it on the way to earth, perhaps it balances out. Well yep, same page shows the foliage in orange where it's IR is emitted, and this is confirmed in the emission spectrum of foliage. Thus more IR is emitted from earth than is received from the Sun.
Next up, does it make us warming measurably? Or is it some insignificant effect?
The moon is the same distance as the earth from the sun, if it had 1 bar pressure wouldn't it have the same temperature? Then why do space suits with 1 bar need heating on the moon?.. Me thinks the gain from a big atmosphere full of CO2 and water is noticeable on cloudy nights and so yes, I think it's clear.
Yeh OK, so we need to reduce carbon based fuel use. Well we need to do that anyway since they're running out. And where's the big problem here?