In other words, average global air temperatures ARE NOT BEING affected by the measured CO2 changes, but demonstrable CO2 CHANGES have taken place.
It's not clear from the article from which the graph was obtained whether the temperature readings referenced are global or local to the Vostok ice core site; I suspect the latter because I don't think the globe has seen that much temperature variability over the last 40 years.
The question of whether or not average global atmospheric temperatures are being influenced by rising CO2 concentrations is the primary question being discussed. The fairly rapid increase in global temperatures over the past 25-28 years has been cited as a good indicator that the influence of GHGs due primarily to fossil fuel burning and other human activities is affecting the Earth's climate to some extent. Accurately attributing the amount of change due to the human influence vs. natural causes of variability is very difficult.
What is the predicted CO2 change that the global warmist eco-enviro's fear?
From my reading, an increase in global temperature more rapid than 2.5-3 degrees C per century is more likely to result in the collapse of natural ecosystems rather than the adaptation of natural ecosystems. I just wrote a bit on another thread about what "sensitive" means, but to be brief, a "sensitive" ecosystem will respond more rapidly and drastically to change in a climate factor than a non-sensitive ecosystem. How it changes depends on the ecosystem.
AS I inderstand their previous "crisis summaries", we have already gotten about 1/3 through the maximum rise in CO2 they fear.
That's hard to tell. Peak CO2 concentrations could be as high as 550 ppmv, but I think most models end up at 475-500 ppmv. We're at about 360 ppmv now, up from 280 ppmv. Your estimate is in the right range.
But we've not seen any massive increase in temperatures. (Yet - temps (if they've risen - and that is debatable) are only up 1/2 -1/3 of a degree.)
It's a cumulative effect. Say you lay down on a bed. You get covered with a sheet. That allows some heat retention. Then the sheet gets covered with a blanket. You'd stay warmer, correct? What would happen if the blanket was then covered with a down comforter?
We may just now be reaching the point where the temperature effect is noticeable.
Why then are they predicting so large a temp increase, if so little is already changed?
See above. The key phrase is "positive feedback"; quantifying that is still in its early stages and therefore quite uncertain.
Do their computer models add a fudge factor to continue "ramping" temperature UP after the CO2 levels are stable? Or are they predicting massive failures of everything (global folloding, drought, feast, and famine) based on the 1 degree rise?
Not sure on the first question, no to the second question. A total 1 degree C rise wouldn't be bad at all, even a 1 C rise in the 21st century over where we are now. But as I said, a 2.5-3 C change over 100 years is considered by many ecologists to be unadaptable by natural ecosystems.