Does smoking cause lung cancer? Around 90% of the 1.6 million new lung cancers diagnosed worldwide every year are directly linked to smoking. The scientific research evidence linking tobacco smoke to a range of diseases over the past half-century is extremely robust.

On the other hand, the fact that not everyone who smokes develops lung cancer proves that tobacco is not fatal to all smokers. But how do we know that all these cancers can really be linked to smoking? After all, there are lots of environmental toxins around.

Almost six decades ago, US researchers first published their unexpected finding that tobacco was strongly implicated as a carcinogen. At the time, more than half of all adults smoked, and smoking was considered little more than a pleasant vice, so this was surprising news.

It was a PR disaster for the tobacco industry. Unwittingly killing millions of people who buy your product is hardly good for business. However, deliberately misleading the public about the dangers of smoking would be immoral, if not actually criminal.

The industry had a clear choice: accept the strong scientific evidence linking tobacco smoke to a range of serious health problems – which meant accepting taxes and close regulation – or fight the science itself. It chose to fight, and brought in PR experts to draw up a smoke-and-mirrors plan to convince the public that there was "no sound scientific basis" for the "sensationalist accusations" being levelled against tobacco by what they smeared as publicity-hungry scientists trying to get public funding for their research. This became known as the Tobacco Strategy.

A battle for the hearts and minds of the American public was under way. The key PR advice to the tobacco industry was that "scientific doubts must remain" about research linking tobacco to smoking. The massive disinformation campaign included funding 'friendly' researchers to research links between just about anything other than cigarettes with lung cancer. As the evidence against tobacco piled up, so too did tobacco industry spending – and ingenuity.

It set up scientific-sounding front organisations such as the Council for Tobacco Research and pumped over $100m into biomedical research in an ever more desperate effort to maintain the impression that there were many causes of lung cancer, and so it was unfair to single out tobacco.

The tactic was enormously successful. Regulation of tobacco was delayed for decades as a false debate played out in the media, with ever more colourful 'alternate' theories distracting from the central fact that tobacco is a potent carcinogen.

In response to evidence from several thousand scientific papers showing an unequivocal link between tobacco and fatal diseases, US tobacco giant Brown & Williamson in 1967 coolly stated: "There is no scientific evidence that cigarette smoking causes lung cancer and other diseases."

Looking back, it seems almost absurd that blatant, persistent lies and propaganda could possibly compete against the huge body of medical and scientific evidence, but it did – and it's happening again. Why? Because doubt is part of the scientific process, a process that examines all evidence and discards what cannot be substantiated.

However, few among the public or the media are familiar with how science works, and this makes it vulnerable to misrepresentation. By taking genuine scientific uncertainties out of context and exaggerating them, the tobacco industry's PR operatives were able to give the false impression, amplified via the media, that the "science isn't settled". A tobacco industry memo from 1969 set it out plainly: "Doubt is our product, since it is the best means of competing with the 'body of facts' that exists in the minds of the general public."

SJ Green, former director of British American Tobacco, owned up to this duplicity when he later stated: "A demand for scientific proof is always a formula for inaction and delay, and usually the first reaction of the guilty. The proper basis for such decisions is quite simply that which is reasonable in the circumstances."

Key to the tobacco industry's disinformation campaign were certain once-respected senior scientists, including retired physicist Frederick Seitz, who went to work for tobacco giant RJ Reynolds and argued vehemently on its behalf against regulating second-hand smoke. Seitz's expertise was in physics, not cancer or epidemiology, and he was simply not qualified to challenge the science, but his reputation meant that his (non-expert) views were taken by the press and public as having scientific weight.

Seitz was also chairman of the George C Marshall Institute, a neo-liberal think tank that aggressively promoted 'free market' solutions and had a visceral contempt for 'pinko' environmentalism. Seitz and others ran similar campaigns to falsely dismiss the scientific evidence linking CFCs and ozone depletion, as well as acid rain and industrial emissions.

As the cold war ended, the think tanks turned their anti-regulation zeal against the science of and climate change, correctly identifying environmental science as a growing threat to the 'freedom' of corporations to maximise profits by being able to continue polluting with impunity.

Backed by billionaire energy industry benefactors from ExxonMobil and the shadowy Koch brothers to high-profile politicians such as Sarah Palin and the Tea Party movement, today's deniers have dusted off the Tobacco Strategy and proven once again that doubt, mixed with disinformation and backed by a big budget, can trump the entire output of the scientific establishment.

Today's trillion-dollar fossil fuel industries, like the tobacco companies before them, are determined to prevent any regulation that could affect their bottom lines. This same 'light touch' regulatory mindset allowed Ireland's rogue bankers, builders and their political allies to engineer our financial fiasco.

Quite simply, the science of climate change is a threat to corporate profits. And since scientific facts are facts, the name of the game is once again to create doubt about these facts, and doubt about the motives, credibility and personal integrity of scientists and the scientific process itself.

"They want to continue a 20-year assault on climate research, questioning basic science and promoting doubt where there is none," said Michael Mann, a top US climate scientist. Penn State University ethics professor Donald Brown recently wrote: "The international community should find a way of classifying extraordinarily irresponsible scientific claims that could lead to mass suffering as some type of crime against humanity."

This view was echoed by former president Mary Robinson in a recent interview with this newspaper in which she sharply criticised "those lobbies… who are trying to bend the science all the time".

These are serious allegations. How do we know the 'debate' is deliberately fraudulent? Well, if there were a genuine debate about the science of climate change, it would be reflected in scientific literature. Professor Naomi Oreskes of the University of San Diego published a review of 928 peer-reviewed scientific articles. Not a single paper from this huge study disputed the basic science of global warming and its human causes.

Since the scientific consensus is robust, 'contrarian' scientists have abandoned scientific journals and instead used the media to propagate their "dissenting views".

Anyone familiar with the scientific process would have smelled a rat immediately: if one scientist genuinely believes another's work is flawed, they submit their evidence to a recognised journal, to be reviewed by a panel of expert peers prior to publication. This is how genuine science is done.

Ironically, the media's effort to present a 'balanced debate' leads to further distortion, with views representing probably no more than 2% of climate scientists often given equal billing with those of the majority. This is known as 'bias in balance', and shows the profound vulnerability of journalism to being manipulated by its own conventions.

The energy sector hasn't a shred of science to defend its manifestly improbable claim that continuing to pour billions of tonnes of fossil fuel emissions into our finite atmosphere can do anything other than ratchet up global temperatures and lead to disastrous ocean acidification. The basic physics behind CO2 and atmospheric warming is over a century old, and is as robust as our understanding of evolution, plate tectonics or germ theory.

In fact, the onus must be on climate change deniers to prove scientifically how the laws of physics somehow don't apply when it comes to CO2 and other man-made emissions.

Professor Jean-Pascal van Ypersele, vice-chair of the Intergovernmental Panel on Climate Change (IPCC), recently condemned the "organised" attacks on climate science that did so much to sabotage December's climate change summit in Copenhagen. "It is a very similar process to what the tobacco industry was doing 30 or 40 years ago, when they wanted to delay legislation," he said.

While we dither, the world burns. As Ireland shivered last winter, Greenland experienced its highest temperatures ever, with astonishing increases ranging from 3.8°C to 8.8°C above the 1971-2000 average. Since 2006, another 1,200,000,000,000 tonnes of Greenland's ice mass have disappeared. Changes on this scale are beyond even the worst-case projections in the IPCC's 2007 report. Destabilisation of the Greenland ice shelf would redraw the map of the world. There is enough water tied up there to raise sea levels globally by 6.5 metres. That puts Ireland's major cities under water. Once an ice shelf is committed to collapse, no force on earth can reverse it. The only question is how long it takes.

Ideologically motivated commentators will claim that sea level rise is a manageable issue. They say the same about ocean acidification, biodiversity collapse and resource depletion. As we have seen in Ireland, most economists struggle even to understand economics; it is foolish to expect them to do better in predicting the impact of climate change than they did regarding the property bubble.

Ireland should, in time, recover from its economic trauma, but all the gains human civilisation has made in recent centuries are now on the line, a major new UN report has warned: "Climate change may be the single factor that makes the future very different, impeding the continuing progress that history would lead us to expect… it can derail human development".

There's no denying it.

John Gibbons is a specialist environmental writer and commentator, and blogs at ThinkOrSwim.ie

A reliance on science

Why we must trust the experts, not the sceptics, on climate research

Blind trust is foolish, but so is reflex scepticism. We trust surgeons enough to let them cut open our flesh and repair our organs. We trust pilots, engineers and air traffic controllers enough to risk flying in metal tubes. Mistakes will still occur but, on balance, we choose to put our faith in qualified experts every day.

Similarly, we must trust scientific experts on scientific matters. Why? Because there are simply no workable alternatives.

Yes, we should query their credentials but, in the end, if world-famous bodies such as the National Academy of Sciences or the UK Royal Society tells us unequivocally that climate change is real, and represents a profound and urgent threat to humanity and the systems on which we depend for survival, we must take heed.

There is a thin line between healthy cynicism and wilful stupidity. Rational decision-making means acting on the best information to hand, even if it is incomplete or imperfect. Modern science is not perfect, but it has a strong track record: we ignore its warnings at our mortal peril.