As I understand this summary, which omits the "research," this guy is saying it wasn't a single strike, but the Earth wandering into the remains of a broken up comet that was the triggering event. Sorta like the Millennium Falcon going into the remains of Alderaan.
It really is a scandal that anyone doing this kind of research has to throw in an obligatory reference to the global warming hoax. I guess they have to do that to get funding.
If you just needed a slug of really cold water, drain Lake Agassiz. It had to have happened sometime...