[tuzo29]

2. If CO2 at the poles is NORMALLY lower than CO2 in Hawaii -- should we even be comparing the two readings?

Yes, we should, and we should measure the variation today and take that into account. Your reference shows a chart that does just that. There's about a 5ppm variation across latitudes for CO2 concentration. Not nearly as large as the error bars on the historical data. Not significant.

4. If ice core data agrees with, or contradicts, available data from other long-term sources.

Sure. We have ice cores that take average air from some period of time (a few hundred to a few thousand years) and this shows that variation on that time scale was minimal over the last 800k years. The other two methods mentioned are either less accurate in measuring CO2 levels as they require a model and fitting as the CO2 isn't measured directly (stomata) or the time window that is being average over gets really long (100k years or more for GEOCARB). These are the reasons ice cores are used for understanding the relatively recent past (last 10k to 20k years). The 36 ppm number that is the discrepancy between GEOCARB and ice cores is actually confirmation that both methods are fairly good. If you want the average over 1000 years, look at ice cores. If you want the average over 100k years, look at GEOCARB and compare it to ice core data and take the mean. Doing that over the data window in the chart give us an estimate of about 260 ppm for CO2 levels in the last 200k years. I would want to see more that two data points from stomata that are both above and below the GEOCARB and ice core data to start to give it more credence. If it only reads above the two other more direct measures of historical CO2 levels, that starts to reduce it's validity and/or calibration process. I'm doing this analysis solo here, but I expect climate scientists have done a similar analysis. If there is stomata data out there that is more complete historically than what is in your reference, I'd like to see it.

So we are left with the following: historical levels of CO2 over the last 100k year is around 260 ppm +/- 30 ppm. The ice core location is maybe +5 ppm higher than Mauna Loa. Adding this all up, ice core and GEOCARB data suggests that CO2 levels were below 300 ppm on average in recent millenia. It probably varied around the average, but there were likely clear causes for the variations (volcanic activity, solar activity, etc.). Which of these known potential causes has led to the increase in CO2 levels in the last 100 years? I really want a second option. I want to be able to drive and fly and not worry about it, but I just can't come up with an cause besides humans burning stuff. PLEASE suggest one. I am all ears. If you can't, then consider that we are the cause for the increased CO2. It's disagreeable, but there's not another viable option that I know of. I'm NOT saying CO2 levels never changed in the last 800k years. I'm saying that there were reasons for whatever changes occurred and they happened on a time scale shorter than a few hundred years. I don't know how large the variations were, but there's a big one happening now. Please give me a reason why it's not caused humans.