I have always like this graphic from Global Warming Art:
It puts the current CO2 rise into sharp perspective in terms of historical flucuations, both in its magnitude and rapidity.
Well, even better for impact is the video below from Youtube user CarbonTracker:
Especially intriguing is watching the seasonal rise and fall, the collective breathing of earth’s plant life.
(passed down from Lou Grinzo to MT to here)
A Few Things Illconsidered 
crakar, read this publication by Keeling, it describes some of the problems with early measurements.
Click to access keeling_autobiography.pdf
Many people cannot grasp that CO2 concentrations are very variable over short periods of time. About 20 years ago I was doing some work for a client. For reasons I wont go into he wanted my analytical equipment in his lab rather than take samples and transport them to my lab. Anyway every morning I would calibrate the instrument (a GC) with an air sample since I was mostly interested in the oxygen nitrogen split and wanted to run the GC at the highest temp that would still give me the best split (so i could run more samples in a given time if residence time was shorter). Anyway, he came in one morning and told me that my GC was a piece of crap since it would not give reproducible numbers for CO2 (we were going to be mesuring CO2 but in percent amounts so I wasn’t worried by 300 ppm variation in my air standard.
I told him that CO2 varied since there were trees at the back of the building and the front of the building was right on one of the main roads into the city. I explained that that would account for the increase in CO2 we observed first thing in the mornings. I could never convince him of that and he still blamed the equipment.
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Re: “the other beck”
Please see: http://scienceblogs.com/illconsidered/2011/01/the_other_beck.php (after 7AM EST)
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“How about picking a much longer time frame than the less than 1% of earth history:”
How about picking a time about the same period as humans have existed?
It doesn’t really matter that the earth was molten rock with sulphuric acid raining down for a few score millennia, when it comes to how the climate responds to CO2, does it?
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“55myo Life flourished, no winters, tropics *not* hotter than today,”
But the sun was cooler.
So why wasn’t it a frozen ball of ice?
Higher CO2 concentrations keeping the heat in.
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