comparing at equal pressures gives more of an apples to apples comparison. Since you can clearly see how radically the temperatures fluctuate based on pressure.
Um, well yeah. The temperatures on different planets are very different, even at the same pressure - as you'd expect, given all the other differences, like distance from the Sun, cloud cover, chemical composition and who knows what else. I'm really not sure where you're going with all this. It certainly doesn't show that "the chemistry of the atmosphere makes almost no difference." It just shows that there are a lot of factors that determine temperature. The pressure may be "apples to apples" but nothing else is.
And of course the temperature goes up & down with the pressure at different altitudes; that's the Pressure-Temperature law I linked to earlier. Perhaps I'm missing something, but I don't see what any of this has to do with the Greenhouse Gas effect.
As to trapping heat... CO2 is hardly unique in this feature nor do I see why it plays a special role in the Earth atmosphere.
What's different about CO2 compared to the other, stronger greenhouse gases like water vapour and methane is that it accumulates over a long time.
Water vapour is a stable quantity in the atmosphere (for a given temperature). Any excess simply precipitates out as rain. It doesn't increase, at least not until you start warming the air up.
Methane does accumulate, for a while - but it is broken down by UV light over a period of years, so it has only a short term effect as well. It can still be a problem (e.g. if melting permafrost like the Siberian Traps releases significant methane into the atmosphere, which is a real concern and could trigger other warming feedbacks), but it doesn't build up over a long time, so any direct effects of a methane pulse are short-lived.
CO2 takes centuries to be removed from the atmosphere. This is done by vegetation, to a small extent, but the vast majority of CO2 uptake is done by the ocean. Even so, this is a slow process. CO2 has been building up rapidly in our atmosphere, and even if we stopped emitting ALL anthropogenic CO2 tomorrow, it would still take centuries to return to pre-industrial levels. Worse, much of that CO2 being absorbed by the oceans is being converted to carbonic acid, which is resulting in ocean acidification - a decreasing pH that we've been observing for some time, and is already having measurable results on sensitive ocean ecosystems.
Yep, that looks like a useful graph. It's certainly clear that water vapour has a bigger effect - but the primary point here is that CO2 also blocks outgoing energy. It's in addition to the effect of water vapour. Water doesn't "black out" the effect of CO2, it adds to it, trapping more energy.
While the water vapour effect is bigger, the CO2 effect is added to this - and that is steadily increasing, as the CO2 in our atmosphere increases. This is enough extra trapped energy to change the temperature equilibrium of our planet; we've done the maths. See e.g. Myhre '98 for how this is forcing value is derived, while Puckrin '04 compares our radiative flux models for a variety of greenhouse gas mixes with atmospheric observations, and finds them to agree well.
Have a look here for a comparison of the radiative forcing values of the significant greenhouse gases, particularly the Greenhouse Gases section and this graph; you'll note that CO2 has the dominant effect. Note also that water vapour isn't considered a forcing (cause of change) - while it traps more energy than CO2, that effect isn't increasing or decreasing - it's stable, because the amount of water vapour in the atmosphere is stable, and therefore is not a direct factor in the increase in temperatures we've been seeing.
However, if something else (like CO2) starts warming the planet, the warmer atmosphere will then hold a little more water vapour, which will increase its effect - in which case it will make the pre-existing warming effect stronger, as a feedback rather than a forcing.
Your entire premise is based on the notion that a trace gas with almost no unique spectrum is going to trigger all sorts of dramatic changes in our climate.
It's not just "my" premise; it's accepted by the vast majority of climatologists and atmospheric scientists. The specific percentage of CO2 is not the issue; the effect of it is, and the changes in that percentage & effect.
And I just don't see any evidence of that. The historical record doesn't appear to back it up. We see CO2 concentrations coming AFTER warming in the historical record.
Sure, because there can be other causes of warming besides CO2, such as orbital cycles. And this warming can trigger the release of CO2, e.g. warming oceans hold less dissolved CO2. So when something else warms the planet, CO2 release follows soon after - and then amplifies the warming through the greenhouse effect. 90% of the warming follows after the CO2 release. But none of this prevents CO2 from causing warming, if we release it into the atmosphere ourselves.
We also see periods of time with high CO2 and low temperatures.
There have been such times in the distant past, yes - but solar output was significantly lower then. CO2 isn't the only driver of climate - solar output is of course a major factor, as are orbital variations. The last time CO2 was around 400 ppm was about 3M years ago, for a few thousand years - and temperatures then were about 2-3 degrees higher than now.
I'll be honest, what got me hot and bothered on the issue was the politics... You had Al Gore standing up there talking... I don't trust the man. I also saw a lot of progressive political elements jumping on board and the whole solution to AGW seems very convenient for them.
So don't listen to Al Gore. He's another example of that bad reporting I was talking about. Ignore the "progressive political elements" too. But don't let political biases blind you to what the science is saying!
Don't listen to Al Gore or Anthony Watts or even me - listen only to the papers that are cited. The deniers insist the alarmists are making it all up... who cares, only the science is important. If you read the cited papers themselves you'll find a refreshing lack of politics, unlike all the noise around the subject. Once a clear picture of what's actually happening is obtained, then we can worry about what to do about it (which is certainly political).
As for shutting people out of the discussion, that obviously hasn't happened - there's more noise on both sides than ever. But within the scientific circles, there's only one criteria for whether you get a voice - you have to have data to back your conclusion, obtained by solid methodology that passes review by your expert peers. If you don't have solid data, you don't get to publish doubtful conclusions. You'll have to agree that's for the best.
Anyway, this discussion's been fun & all, but I've spent way too much time writing all this out and finding appropriate citations. Please do read at least the abstracts and conclusions. If you don't find those convincing, then nothing else I say will help. Best of luck with it all.