The data is pretty cool - but has its own problems with uncertainty, of course. Basically, this is how those uber-long tens of thousands ago in the past temperature plots get created that show multiple warming and cooling cycles (and the famous plots that show that CO2 levels lag temperature and do not precede temperature changes historically due to the ocean's response to temperature change).
I could not agree more with this. Funny thing is his theatrics almost certainly hurt the cause he espouses.