"Roth is a geologist by training and a former science teacher who has worked as a natural resource specialist at the monument for 17 years."
BUNK - Pure environmental babble-trash ... The MAIN explination that historical geologists give for the mass extention at the Permian/Triassic boundry is changing sea levels caused by GLACIATION and GLOBAL COOLING, not carbon dioxide.
"Although the cause of the Permian mass extinction remains a debate, numerous theories have been formulated to explain the events of the extinction. One of the most current theories for the mass extinction of the Permian is an agent that has been also held responsible for the Ordovician and Devonian crises, glaciation on Gondwana. A similar glaciation event in the Permian would likely produce mass extinction in the same manner as previous, that is, by a global widespread cooling and/or worldwide lowering of sea level."
http://hannover.park.org/Canada/Museum/extinction/permcause.html
Actually it appears the site you cite, and a handful of others, are flat out wrong or confused.
Certainly the more recent cites and articles and the more fully explained articles, and by far the majority, attribute the Permian extinction to warming, not cooling.
I wonder if some sites are confusing the Permian extinction and the "Snowball Earth" hundreds of millions of years earlier.