Please tell us where you found this sentence, and in what context. It would also be helpful if you could tell us which parts of the sentence confuse you, so we don't waste time explaining things you already understand.
Assuming that the source is the global warming article on sfgate.com, the situation is:
--- Al Gore campaigned to raise awareness of "global warming" which is a misnomer for "climate change" and involves major changes to "normal" weather patterns.
--- The snowfall was so extensive that some thought it "proved" global warming was a hoax or exaggerated.
--- So the writer says that some "unbelievers" would take pleasure in sneering at Al Gore and others concerned with "global warming".