PPS I have had a chance to listen to the video, and in particular to the question and answer session of the final 30 minutes or so. Here are my comments on that, as posted on Bishop Hill (on the post linked to in the PS hat-tip):
In my opinion this entire sorry episode goes straight to the heart of the difference between the way alarmists like Williamson see the world, and the way normal people view the world. Alarmists seem to want their models, theories and opinions to be accepted as established fact. But the reality is their shaky theories are full of poorly supported conjecture and extrapolation.
Eric Worrall on WUWT, quoted by Dellers who has criticised Williamson's facile alarmism: http://www.breitbart.com/london/2017/01/09/delingpole-how-i-totally-crushed-the-ocean-acidification-alarmist-loons/