OPINION: It's either the greatest threat civilisation has ever faced, or a hoax perpetrated by fraudulent scientists. Opinions on both sides of the debate are so strong that one side barely speaks with the other. The two groups read different newspapers and websites, and immerse themselves in information that reinforces their existing prejudices.
So what would happen if you took two assertive people with diametrically opposed opinions on human-induced climate change, put them together for a month and filmed them attempting to change each other's mind?
We are about to find out, since this is the premise of an intriguing documentary I Can Change Your Mind About Climate on ABC1 tonight, followed by a Q&A with a live audience.
Our two protagonists are Nick Minchin, the retired Liberal senator who still wields substantial backroom influence, and Anna Rose, the 28-year old co-founder of the Australian Youth Climate Coalition. Each had the opportunity to nominate seven experts from anywhere on the planet to help with their case and producers threw in four wildcards.
Anna has written a book, Madlands, which describes her four weeks travelling and arguing with Nick, meeting 18 experts on four continents while trying to organise her wedding for two weeks after her return to Sydney.
For Anna, the documentary posed the real risk of providing a false balance: elevating the arguments of deniers to the same level as the opinion of almost all climate scientists. As my colleague Stephan Lewandowski has argued, the producers would more fairly represent the scientific debate by giving Anna 97 experts and Nick at most three. But they would have selected someone else if she said no, so Anna stepped up to the plate.
They are two smart and articulate people: Nick the consummate politician, with a quick wit and rapier-like skills in argument; Anna not hardened in the parliamentary fire, but confident, well-informed and more than able to hold her own. So how can two clever people have different opinions on such an important topic, which is surely amenable to a calm and logical consideration of the science?
When it comes to the science of climate change, Nick probably subconsciously imbues climate scientists with all the characteristics of the people he has dealt with in politics. He assumes self-serving behaviour, dishonesty, fraud and a willingness to bend the truth without batting an eyelid. It is no wonder that someone steeped in this culture thinks the rest of the community acts in the same way.
His failure to understand the science becomes clear with his choice of experts. They range from self-proclaimed ''rocket-scientist'' David Evans and his wife, Joanne Codling (stage name Joanne Nova ), who run a blog from their home in Perth, to Republican attack-dog Marc Morano, whose website climatedepot.com regularly smears climate scientists and publishes their email addresses, whereupon his readers then follow up with a barrage of emails including death threats. I know because I have been on the receiving end.
Only one of Nick's champions is a climate scientist, Professor Richard Lindzen, renowned for having spent more than 20 years trying, and repeatedly failing, to find errors in the theory of human-induced climate change. Lindzen, like Nick in the 1990s, has also questioned the link between passive smoking and lung cancer.
With the pick of the world's leading scientists available to her, however, Anna carefully selected people she thought would most influence Nick. Hence she left out James Hansen, one of NASA's most respected climate scientists whose published predictions from 30 years ago are coming true today, as Nick regards Hansen as a fraud (try googling ''James Hansen fraud'' for a journey into the weird and ugly world of the climate denier).
Instead she chose Zac Goldsmith, a British conservative politician who shares Nick's political ideology but gets his climate science from scientists, not bloggers.
Politicians are at a significant disadvantage when trying to grasp the seriousness of climate change. Their instinct is to search for compromises and to negotiate outcomes. But nature doesn't compromise. The earth's response to human CO2 emissions will be what it will be, and no amount of political sophistry will make the slightest difference. When the Arctic becomes ice-free in summer, probably by mid-century and possibly much earlier, no amount of political posturing will turn the sea back into ice.
Unlike in politics, there really is one true answer to questions of science, and it is the aim of scientists to elucidate that truth.
Scientists are uneasy about the exercise in ''balance'' that this documentary represents, but I believe that if your aim were to expose the weakness of Nick's side, giving him 50 per cent (or more) of the airtime is not necessarily a bad thing.
Professor Michael Ashley is in the Department of Astrophysics at UNSW.
This opinion piece first appeared in The Sydney Morning Herald