Maybe so. But the key point I've made (numerous times) is that the maximum natural peak in atmospheric CO2 concentrations, over the past 640,000 years now with the EPICA core, is about 280 ppm (I'll accept +/- 10 ppm error). No matter how the core data is sliced/spliced/or diced, that is a salient fact. The more modern ice core data (Siple or Taylor or Law) starts there and then shows the increasing CO2 concentration commencing in the 1700s, and merging quite smoothly into the Mauna Loa measurements.
And it's not like we didn't know burning wood and kerosene and oil and gas would put CO2 into the atmosphere; so it shouldn't come as much of a surprise that atmospheric samples confirm that.
Not exactly. The core data shows error bars to 300ppm and the core data averages readings over 30 years to 50 years (mostly depending on the age of the sample). So there are blips of CO2 that got averaged out and it's essentially the same science as today's models (e.g. warming releasing CO2) to figure out how big those blips might be. It's not likely that any blip exceeds today's 380 ppm but I wouldn't rule it out either.