A common global warming argument is to show a graph showing a correlation between increases in temperature and CO2 over millions of years. A correlation does not necessarily imply causation, but in the presence of a strong theory that CO2 is a greenhouse gas, the graph is pretty convincing.
The only trouble is that a closer examination shows that the tightest correlation is between the temperature increases and the CO2 increases 800 years later. This suggests that the temperature increases is causing the CO2 increase, and not the other way around.
The global warming scientists acknowledge this. They say that in typical past warming periods, the Earth warmed for 800 years before causing an increase in CO2. The CO2 then exacerbated the warming for rest of the typical 5000 year cycle, before some unknown force started a cooling trend. They say that the CO2 still causes warming, it just hasn't started the warming cycle as it has in the last century.
All that may be true, but what does the graph prove of relevance to us today? Nothing that I can see. It doesn't give any evidence at all that the recent warming was caused by CO2 or humans. It doesn't tell us whether CO2 has anything to do with the duration or intensity of a warming cycle. It doesn't give us any reason to cut back on CO2 emissions.