Seeing the environmental forest

A reader with the pen name pjscirkus commented on my post debunking Tom Luongo's nonsense .  Rather than add anything useful, he/she proceeded to spew enough nonsense of his/her own that I thought it best to answer here rather than in the comment thread.

 One of the persistent puzzles about the ice ages is the appearance of an 600 to 800-year lag between Antarctic temperatures and atmospheric CO 2 levels.

There is a persistent idea floating around in some circles that the current episode of global warming is due to some sort of natural cycle.  Why not?  Previous episodes of global warming or cooling were natural.  Beyond the data that shows that this episode of global warming is due to CO 2 , the main problem with that idea is finding a natural cycle fits.