The soy rotted in the trains

Logical answers to a couple of side effect non-issues of climate change denial.

First: why's this climate change thing so bad? I mean, I might like wearing shorts in November and I hear monsoons are fun! The most famous modern-day example of this I'd say is Vladimir Putin's attitude that a thawed Siberia would make him the de facto agribusiness world leader.
But forget any specific details here for one moment and let's establish one thing. Humans don't deal well with change. Fifteen hundreds years ago, the central-Asian steppe went through a little climactic hiccup. Did the Mongols get their population under control? Did they just institute new farming/ranching policies? No, they ransacked half of Eurasia. Eighty years ago, American farmers' reaction to their self-imposed overproduction crisis and the resulting ecological disaster was to amplify production. Humans do not deal well with unfamiliar situations. The little progress that's been made throughout history has been made by a few superhuman intellects dragging the unwitting masses kicking and screaming to a better lifestyle and there are severe limits to the social impact of progressive visionaries. Apes will be apes.
If we can't make the little change that would be necessary now to deal with a crisis before it spirals out of control, what would make anyone think this species could handle the necessary changes fifty, two hundred or a thousand years from now to ride the mounting wave of its own recklessness? The appropriate metaphor is not "sink or swim" but "stop splashing or you'll drown yourself."
It doesn't do to be blindly optimistic. The specific changes which will come about are terrifying precisely because they are unpredictable. How will Canada deal with Texan tornadoes? How would Japan handle a fishing industry collapse? How would the British Isles cope with a Gulf Stream shift of a few degrees of longitude, if they lost their hot-water-bottle and suddenly had to deal with the fact that they're on the same latitude as Newfoundland?

Second is the confusion about why anyone would knowingly deny something so catastrophic. I mean, if everything goes to shit, don't we all suffer?
Well... no. The rich would not. For one thing, the richer you are, the more mobility you possess. If you can buy yourself hilltop estates anywhere you want, you're less inclined to give a shit about rising sea levels. If you're rich enough to own entire countries, as many oil/banking/military "machers" are, then what's a few million or half a billion dead of starvation and social unrest? They're just disposable recruits. Capital.
Also, "rich" is an intrinsically comparative term, and the comparison only improves with spreading poverty. Human misery is the greatest resource of the rich, not only because it provides them with willing masses primed for subjugation but because it implicitly feeds the instinctive desperation to compare one's social standing favorably to others'. Shrinking the pond is, instinctively, a valid means of ensuring one's social rank as opposed to growing into a big fish. The worse off the people under you are, the less able they are to stand up to you, the better. You don't need a roaring economy if a plummeting one will ensure families are desperate enough to sell you their children. Social power is not expressed in absolute values but as power over others, and the misery of the poor is the tried-and-true route to that blissful inequality, not the well-being of the rich.
Here's a quote that tends to get ignored in the usual willful misinterpretation of Atlas Shrugged: "that so long as men struggle to stay alive, they’ll never produce so little but that the man with the club won’t be able to seize it and leave them still less, provided millions of them are willing to submit - that the feudal baron did not need electronic factories in order to drink his brains away out of jeweled goblets and neither did the rajahs of the People's State of India".
The rich of today, the barons of industry, the Fortune 500, the petty tyrants of corporate states like the U.S. are those barons and rajahs of Rand's description and not her pipe-dream of enlightened progressive social engineers, and though they fear change they also drool at the dream of change which would impoverish all others around them to the point of empowering them and their private armies to depraved excesses and sadistic pleasures even Caligula and the Marquis de Sade could never have imagined.
The rapist's dream of ineffective opposition drives humans to accept apocalyptic scenarios, so long as in that broken world they can maintain or improve their relative standing. And the difference between rich and poor is that the rich can afford to convince the poor to bring about such scenarios.