The essential characteristic of those who deny global warming is that they seem to be unable to see a larger picture. Instead they seize on one event or phenomenon which proxies for their entire argument against global warming. I have touched on this in the past. For example, a friend of a friend decided that the arctic ice was coming back, and that of course that one occurrence negated all global warming. Besides the fact that the overwhelming evidence for global warming does not rest upon that one issue, he was also wrong.
Of course they don't have to be wrong about one piece of evidence and then be right about there not being any global warming. For example, some will point out that there's an expanding glacier in the Mt. St. Helens, but claiming that means there isn't any global warming ignores the fact that most glaciers in the world are rapidly melting.
Global warming deniers are characterized by an inability to weigh all of the evidence. They seize upon something and hang on to it like a bulldog. They are almost never climate scientists. They always have some other goal than to assess all of the evidence. They see something and claim "gotcha", when all they have is "cherry picked" data.
That this intellectual disability so pervades our population is very dangerous. There is the chance that an Atlantic ocean current that flows north from the Gulf up to Greenland and back that has for centuries warmed Europe, giving it a climate comparable to the Northern U.S. even though its latitudes compare to Alaska and Canada, could be disrupted by the warming of the oceans. In that case Europe could undergo, as a result of global warming, a rather severe local cooling. Such an occurrence could completely quash all efforts to suppress our pouring CO2 into the atmosphere, with the ironical effect of guaranteeing an eventual warming of the planet beyond its ability to support human life. It's just beyond human mental ability to keep in its collective mind the opposing pieces of data, that Europe will freeze for ten years or so, while at the same time the planet overall is warming far past turning around. If this does indeed happen we're doomed.