The words "global warming" provoke a sharp retort from Colorado State University meteorology professor emeritus William Gray: "It's a big scam." And the name of climate researcher Kevin Trenberth elicits a sputtered "opportunist."

(Grey repeated his assertion despite the publication of a meticulous refutation of his claims by a group of leading climate scientists.) 

At the National Center for Atmospheric Research, where Trenberth works, Gray's name prompts dismay. "Bill Gray is completely unreasonable," Trenberth says. "He has a mind block on this."