Why don't you try me on that one, instead of setting up a strawman based on presumed response?   I promise to keep my rebuttal purely scientific. 

We have reasonably robust proxy data going back far further (particularly ice core data, with isotopic ratios in the water as a measure for temperature and entrained air bubbles for CO2 concentration). indicating a strong linkage between temperature and carbon dioxide levels. Does it establish causality? No. Does it suggest the two are very closely related? Definitely. Does that suggest we should be careful about tampering with it? Yeah, it kinda does. 

Shortness of record isn't an obstacle, when within that dataset you have a significant anomaly that processes can't explain. Particularly when said anomaly runs alongside a sudden mass influx of carbon dioxide due to industrial activities.  Since we know CO2 and temperature seem linked, it's very likely all three are. That is to say, our carbon is likely the cause.