JC, before you complain that these data aren't calibrated in centigrade degrees, let's think about how YOU would do the experiment you're demanding.
You say you want to see how much of a temperature increase is caused by raising CO2 levels in our atmosphere from 280 ppm to 400 ppm. You want to do an experiment in which a number will pop out, in units of degrees centigrade or degrees Fahrenheit that is directly applicable to the Earth's atmosphere. That is, we would have some black box set up which we would let run for a few minutes and would then read, directly off some dial, 0.9C or the like. Thus we would know that the increased CO2 in the Earth's atmosphere has caused precisely that much of the warming we've experienced.
Right?
If we had another Earth, or sufficient control of this one, we could do it "in situ". We could set up the Earth with a 280 ppm atmosphere, take some measurements, then jack up the CO2 to 400 ppm and start taking more. We wouldn't let ANYTHING else change. Alternatively, we could get our hands on two Earths (or even more) and set up CONTROL EARTHS: Earths in which we change NOTHING but which would undergo any uncontrolled changes our Earth's were heir to. So... do you know where we could get a couple of extra Earths? Hmm... that's a problem.
So, we have to arrange some sort of setup that we can assemble in the space we actually have available to us which will mimic the processes on Earth that we want to investigate. And what are those processes?
Incoming solar radiation
Outgoing terrestrial radiation
Atmospheric mixes with varying levels of CO2
Clouds of all sorts at a wide range of altitudes
Oceans with currents and mixing and biota and ice and pretty sailboats in the sunset
Storms from gentle zephyrs to raging typhoons, clockwise and anti-clockwise
Volcanic aerosols
Soot aerosols
Polychlorinated fluorocarbons and ozone
Allbedo that varies with temperature
Humidity that varies with temperature
Farts
And a hundred other factors
Again, hmmmm..... that's going to be a little tough to fit into the space we've got. We need to SIMPLIFY. All you're really curious about is the effect of CO2 on the retention of solar energy, right? All those other things certainly have effects on the Earth's temperature, but it seems like a fairly safe assumption that they'll do what they do with or without CO2. Clouds will be clouds, volcanoes will be volcanoes and farts... well, the point is that we don't need them to see what we can see. Now WITHOUT all those things, we will not be able to construct an experiment that will directly tell us how much warming 120 ppm will cause. What can our experiment tell us.
Well, let's back up a little bit on both sides. Temperature is sort of a secondary effect. When I put a pot of water on the stove that I want to boil, I don't put centigrade degrees into it, do I. I put energy into it. The water's temperature is an external expression of how much energy it's got in it. Right? The more energy in the water, the higher its temperature. Now we can get fancy dan here and differentiate between potential and kinetic energy and thermodynamic and electromagnetic and nuclear and chemical and phlogostimaticalaciousnephrillianistic. But, in the real world, the sort of stuff we're dealing with pretty much all boils down to heat. We'll put some energy in (as solar radiation), some will come back out (as terrestrial thermal radiation) and the difference between the two will tell us how much energy the CO2 trapped.
I'd love to carry on with this style, but I have to get underway. This Monday is our 30th anniversary and the wife and I are taking a romantic weekend getaway.
What I've been trying to steer you towards, JC, is that the experiment we've been moving towards here is precisely the experiment that produces the CO2 absorption spectra with which your demand for an experiment has been fairly consistently answered. The data in that graph tells us (perhaps not you, but, by education, that's actually correctable) how much energy will be trapped by CO2 in the atmosphere. The calculation gets a little complicated. It involves something called spectral intensity - a measure of how much energy is present in each little vertical sliver of that graph. This allows us to calculate the energy in those divots that CO2 puts into the raw spectrum of IR the warmed Earth is radiating. And with some real numbers: like the spectral intensity of the solar radiation and that of the Earth's surface and the behavior of the atmosphere in all its different layers, we can come up with a fair number. Now, as we noted in the beginning here, there are a heck of a lot of other things going on in a planet this size that have their own effect on the final result. It's not a simple thing to take them all into account, but we can try. However, the crucial step, the one in which we figure out whether or not CO2 will cause temperatures to increase and ABOUT how much; that's been done, JC, over and over and over again.
The greenhouse effect is settled science. That CO2 is a greenhouse gas is a demonstrable fact. It's time to move on son.