There isn't any weekly data for 3.5-5 million years ago strangely enough, you won't even get that fidelity over the last 100 years because its simply and obviously impossible to work out which week a spec of ice was from with any reliability. But yes, I know you are being facetious so I'll just let you know how we know what we do about historic CO2 levels, there are many ways to do so actually and this is why we have such an accurate picture of past levels.
You can analyse fossilized shells and determine the level of carbonates in them, and thus infer what the ocean acidification would have been and from that atmospheric CO2 levels.
You can look at tree ring data from fossilized samples. Obviously trees grow faster in warmer climates, and you can date the trees using several radio-isotopes giving you an understanding of temperature at any given time.
The main method though is looking at the pockets of air that are trapped between ice stored in ultra cold polar and mountain top regions which never thaw and so provide a very long and continuous record.
Again really the point is that we know there is a historic correlation between temperature and CO2, and yes we even know that the temperature increase lags behind the CO2 increase and not the other way around as I know you must be tempted to claim. The ASX reached a new 5 year high today and that was considered news worthy, so a 5 million year high is obviously a pretty significant event.
I know you don't care about any of this though so I'll give you something to have a good laugh at with your fellow skeptics and to help you gain some reputation among the same. Did you know that the temperature in the Stratosphere is dropping fairly rapidly? That has got to be the killer blow to climate change, surely.
