Of course it has an effect, it acts as insulation. Did you forget about how greenhouse gasses absorb infrared radiation? That means it blocks it. Well, it slows it's escape, ultimately. And we require it to be slowed to some degree or we'd freeze and that's no good either. What I said previously was that heat is most evident at it's source. Nothing special there. Why would it get warmer first in the upper atmosphere when the primary infrared source is from the surface?
I'm glad you bring up the water vapor. This is a good example. Yes, unit for unit, it does absorb a fuck load more than CO2 does. Absolutely. It adds a great deal to our layer of heat insulation. However, water vapor doesn't stay in the atmosphere nearly as long as CO2, does it? It's levels could never sustain a 50% overall increase without something else being really out of whack. No, it pretty quickly condenses and stays at a general equilibrium in time and cycle with everything else. CO2 on the other hand can be in the atmosphere for thousands of years before it gets absorbed by a tree or the oceans or something else, and the Earth has a finite capacity of CO2 sinks. All that previously sequestered CO2 has to wait in que to enter the sink. This becomes the positive feedback we are currently setting into motion. Eventually the point comes when it becomes runaway. So we should just ignore that? This much CO2 would never be in the air right now if it wasn't for us. The only practical options we have right now is to try and reduce the rate we put out. Personally, I don't see this being solved until something radical like fusion power comes along. I don't think we could ever hope to produce the amount of glass and aluminum required to replace the amount of energy we get from fossil fuels with things like solar panels and wind turbines. We are way too power hungry as a species. But it's a start, and every bit does count in the end.
I said it previously.. CO2 may be a small factor, but that doesn't make it insignificant.
