The grim findings of the IPCC last year reiterated what climatologists have long been telling us: the climate is changing at an unprecedented rate, and we're to blame. Despite the clear scientific consensus, a veritable brigade of self-proclaimed, underinformed armchair experts lurk on comment threads the world over, eager to pour scorn on climate science. Barrages of ad hominem attacks all too often await both the scientists working in climate research and journalists who communicate the research findings.

The nay-sayers insist loudly that they're "climate sceptics", but this is a calculated misnomer – scientific scepticism is the method of investigating whether a particular hypothesis is supported by the evidence. Climate sceptics, by contrast, persist in ignoring empirical evidence that renders their position untenable. This isn't scepticism, it's unadulterated denialism, the very antithesis of critical thought.

Were climate change denialism confined solely to the foaming comment threads of the internet it would be bad enough, but this is not the case – publications such as the Daily Mail, Wall Street Journal and other Murdoch publications give editorial support to this view. Worse still, a depressingly large number of denialists hold office around the world. Australia's Tony Abbot decreed climate change to be "a load of crap", and a sizable chunk of the US Republican Party declare it a fiction. Even in the UK, spending on climate change countermeasures has halved under the environment secretary Owen Paterson, who doubts the reality of anthropogenic climate change, despite the fact the vast majority of scientists say unequivocally that the smoking gun is in our hands.

So given the evidence is so strong against them, then why do these beliefs garner such passionate, vocal support? It's tempting to say the problem is a simple misunderstanding, because increasing average global temperature can have paradoxical and counterintuitive repercussions, such as causing extreme cold snaps. The obvious response to this misunderstanding is to elucidate the scientific details more clearly and more often.

The problem is that the well-meaning and considered approach hinges on the presupposition that the intended audience is always rational, willing to base or change its position on the balance of evidence. However, recent investigations suggests this might be a supposition too far. A study in 2011 found that conservative white males in the US were far more likely than other Americans to deny climate change. Another study found denialism in the UK was more common among politically conservative individuals with traditional values. A series of investigations published last year by Prof Stephan Lewandowsky and his colleagues – including one with the fantastic title, Nasa Faked the Moon Landing – Therefore, (Climate) Science Is a Hoax: An Anatomy of the Motivated Rejection of Science – found that while subjects subscribing to conspiracist thought tended to reject all scientific propositions they encountered, those with strong traits of conservatism or pronounced free-market world views only tended to reject scientific findings with regulatory implications.

It should be no surprise that the voters and politicians opposed to climate change tend to be of a conservative bent, keen to support free-market ideology. This is part of a phenomenon known as motivated reasoning, where instead of evidence being evaluated critically, it is deliberately interpreted in such a way as to reaffirm a pre-existing belief, demanding impossibly stringent examination of unwelcome evidence while accepting uncritically even the flimsiest information that suits one's needs.

The great psychologist Leon Festinger observed in 1956 that "a man with a conviction is a hard man to change. Tell him you disagree and he turns away. Show him facts or figures and he questions your sources. Appeal to logic and he fails to see your point." This is the essence of the problem, and sadly, Festinger's words ring true today: the conviction of humans is all too often impervious to the very evidence in front of them.

Motivated reasoning is not solely the preserve of conservatives. While nuclear power has been recognised by the IPCC as important in reducing carbon dioxide emissions, staunch and uninformed opposition to nuclear power arises often from the liberal aisle. In the furore over the Fukushima nuclear disaster (which has claimed no lives and probably never will) many environmentalists lost sight of the fact that it was a natural disaster, very possibly exacerbated by climate change, that cost thousands of lives. Instead, they've rushed to condemn nuclear power plants.

Angela Merkel's decision to cut nuclear power stations was celebrated by Green activists, but this victory was utterly pyrrhic as they were replaced by heavily polluting coal plants. Nor could it be considered a health victory, as while nuclear power kills virtually no one, 1.3 million people a year die as a result of pollution from coal-burning plants.

Greenpeace remains stubbornly opposed to even considering nuclear power, and has said it is simply too dangerous claiming a figure of over 200,000 deaths and hugely increased incidence of cancers due to the Chernobyl disaster, a statistic exposed as an utter shambles by the journal Radiation Protection Dosimetry.

The health effects of Chernobyl have been well studied over 25 years by the UN Scientific Committee on the Effects of Atomic Radiation: 28 workers died from acute radiation syndrome, and there were 15 fatal thyroid cancers in children. Those who ingested radioiodine immediately after the disaster are at elevated risk of thyroid cancer. No increase has been observed in solid cancers or birth defects.

That this toll is considerably less than people might expect does not take away from the tragedy, but highlights the fact that motivated reasoning occurs on all sides.

The problem is that a vital discussion on a scientific issue can be hijacked as a proxy for deep-seated ideological differences. Depressingly, increasing communication of science merely tends to harden existing opinion. Part of the solution may be to take into consideration the values that impede meaningful progress; there is some evidence that climate change denialists become less hostile when given options which do not obviously threaten their world view.

If the facts of the matter inspire an emotional threat reaction, perhaps this can be mitigated by framing it as something not incompatible to one's world view. A free-market advocate, for example, might respond better to an argument outlining the economic cost of climate change or the fact inaction has a higher price tag than action.

Nor is there any inherent contradiction in an environmentalist being in favour of nuclear power – George Monbiot, Mark Lynas and James Lovelock have written eloquently on the importance of nuclear power in mitigating the ravages of climate change.

If we truly wish to avoid catastrophe, we must be pragmatic and take action. Ideological differences need to take a back seat if decisive action is to be taken. When one's house is on fire, the immediate priority should be putting the flames out, not squabbling about the insurance. Let us hope we realise this before it's too late.

David Robert Grimes is a science writer and a physicist at Oxford University. He blogs at davidrobertgrimes.com. On Twitter he is @drg1985