Yes I see exactly what you mean. Look at a few glaciers and make elementary deductions - that never got anyone into trouble in the past did it?! His whole address is based on a thowaway line about a 50% probability. But the whole subject of risk is it has to be quantitatively assessed. Suppose the risk was actually 0.000005%. Should everyone spring into precautionary action then? And he says 'there is no other question'! Charlatan!
Well, I must say, based on his rationale (and I think there was global warming, WAS, just not anthropogenic) I ought to say that there is serious problem on global cooling.
See, I am a mountainbiker. It is not rare for me to spend many hours in the saddle for several months of the year. I live in Canada (same place where he has seen the glaciers melting) and love the Rockies.
Awesome place to bike, if you are a biker that loves to cough and hack on the way up and go down at an almost suicidal speed on a terrain where brakes do little else other than help you steer.
Nevertheless, I have seen the riding season start later and finish earlier as of the last couple years. No more night riding above the tree line in Autumn and a late start for upper mountain climbing. Reason SNOW!!!
The snow is taking longer to melt and arrives much sooner than it used to (my sample is of the last 15yrs though).
I know my example is not representative to the global scenario, as it encompasses only British Columbia and Alberta, but if I am to be guided by just observation the way he suggests, my buddies and I better start more bonfires at the end of the ride to better enjoy our beers and help the world to warm up a bit again!!!
Oh, and more often than not, by the time the ski season ends and the resorts are closing, you now get another couple weeks of AWESOME snow!!