If there is any relationship between GDP and average temperatures it is a negative one. Canada and Scandinavia are 1st world countries whereas everything around the equator are either third world or threshold countries.
Unless you count places like Singapore, smack dab on the equator and rich as sin. In GDP per square mile, Canada lags behind Brazil and Nigeria.
Anyway, that's not the issue. There are plenty of academic papers, IPCC reports or economic stuff like the Stern report (the only thing I ever read about the issue) which reveal the high costs (there are of course asymmetrically distributed) of an increase of average temperatures around 2 degree. We will probably break the 2° barrier and beyond that it will become pretty nasty.
If higher temperatures cost more, how come all those poor people are living in the hot places instead of someplace cheap and cold like Sweden? How did we afford to make it through the medieval warm period when crops were flourishing?
Climate change denials reminds me of Freud's story about the borrowed kettle.
In this case the three mutually exclusive arguments are something like this: "An increase of average temperatures doesn't actually do any damage to the ecosphere, there is something wrong with climatology, climate change does not really exist."
They're not mutually exclusive. Just because warming would be great doesn't mean it's going to happen. Frankly, with a Dalton or Maunder minimum coming, we're screwed.
Belief in climate change is like a fairy tale. Even though CO2 lags temperatures, it causes them. Even though cloud feedbacks should be negative and are shown to be negative, they must be positive or climate funding will dry up. Even though switching to more expensive power sources will shift all the energy intensive manufacturing to China and India's less efficient facilities, along with trans-ocean shipping of building materials like steel, glass, bricks,and concrete, we must do it to save the environment. Even though we have terms like "arctic wasteland" and "tropical paradise" for a reason, warming is bad.
The real problem is that believers think the warming is caused by overindulgence (sin), and humans know the consequences of overindulgence are painful and bad. A whale, dolphin, or cat would look at global warming and think "free food!" Only monkeys would think something bad has to happen to keep the scales of karmic balance in line.
To a human, the idea that a fat guy sipping a slurpy while barreling down the highway is
saving the planet and helping the poor is absurd. Our little brains, tuned as hunter gatherers, tell us the universe just can't work that way. Our religions all say you can't have something good come from sin, glutony, and self-indulgence. Objective science (which is not what we're getting) would disagree.
Or try this. Divide the world up into random sets of coordinates and temperatures. With a coin toss, increase or decrease the temperature at each point. Does the location become more or less suitable for life? Since the initial temperatures were essentially random, the result should be about 50-50. But we're still in an ice age with far below normal historical temperatures, and much of the planet remains locked in ice, so really there should be a bias toward warmer temperatures improving the conditions at the random locations.
But the answer climate scientists give us is always the same. Any increase is bad. Bad everywhere. Bad for everyone and at all times. In all cases bad. They're nuts, unable to get over their primitive primate instincts and religious conditioning.
