The novels of Umberto Eco suggest that if people want to believe something badly enough, they will only hear what they want to hear. This is particularly true in the current debate about global warming, writes Lisa Jardine.

(Spoiler alert: Key plot details revealed below)

Umberto Eco was in London recently to publicise his latest novel, The Prague Cemetery - a baroque, meandering work of murder and intrigue set in the late 19th Century. A persistent theme of this book, as of several of his earlier ones, is the credulity of those who crave a cause to believe in.

This is a theme that clearly has its equivalent today - which is probably why it continues to fascinate Eco.

Those who have lost faith in a higher order often search strenuously for an alternative belief system to help them make sense of the world. And the more widely held more "mainstream" theories are, the more determined such "non-believers" are likely to become in their search for an alternative.

Image caption Umberto Eco's 1988 novel Foucault's Pendulum has been called the "thinking man's Da Vinci Code"

Many years ago, when I was a novice broadcaster, I interviewed Eco live for BBC Radio. Eco was in London to publicise a book of essays, and was in a contrary mood.

I was glad that in my recent broadcasting training I had been taught how to stop a guest from producing resonating bangs on the air waves by tapping their pen against the microphone stand in time with the points they were making.

You lean forward very slowly so as not to startle them and cause them to expostulate verbally, firmly close your own hand round the offending pen-holding one, and remove it silently to a place of safety. To my relief it worked.

Still, it was the last in a long day of interviews and Eco was barely paying attention to my questions. Until I heard him remark, à propos his love of music, that as a 12-year-old boy in Piedmont, northern Italy, he had started to learn the trumpet.

"So you were the little boy in Foucault's Pendulum, who didn't know how to play the Last Post," I exclaimed.

Eco stopped fiddling with the studio equipment and looked me straight in the eye. "Yes," he answered, "I was that small boy". From then on he responded energetically to my questions, and the interview is one I recall with pleasure to this day.

Trumpet lessons

Foucault's Pendulum, Eco's second novel, was first published in 1988. Together with two accomplices, the protagonist, Jacopo Belbo - perhaps more villain than hero - creates a complex, highly plausible set of documents purporting to come from the ancient secret association of the Order of the Templars in the Middle Ages.

Image caption The Last Post was the protagonist's first "con"

In the book, this proves so convincing that it attracts a determined following of people who passionately believe in the continuity of the Templars, and their quest for the Holy Grail, down to the present day.

The situation gets badly out of hand, and Belbo and his fellow tricksters find themselves pursued by 20th Century Templars who are convinced of the truth of their fabricated documents. This leads ultimately to Belbo's ritual murder by them, in the belief that he is withholding the "revelation", the answer to fundamental questions of the Order.

It is a key incident from Belbo's childhood which convinces him that people can be drawn with ease into believing in a deception, as long as they have a big enough personal investment in the constructed narrative to badly want it to be true.

Here is how Belbo's story goes in Foucault's Pendulum: At the end of the war, in 1945, as Italian partisans were driving back the Fascists, a convoy of freedom fighters arrived in Belbo's village.

Two men killed in action were to be buried in the local cemetery, with full honours. Eager to play a part in the glory of victory, the 12-year-old Belbo volunteered to play the Last Post at the burial, even though he had barely begun to take trumpet lessons.

When the moment came, he rose to his feet and played, slowly and with passion, the scale of C major - all he had as yet learned how to play.

He held the final note for as long as he could for particular effect. The onlookers heard the plangent tones of the Last Post. "Bravo, young fellow," the commander said to Belbo, who felt uplifted by the importance his deception had given him.

If such a simple subterfuge could earn him unstinting approval, Belbo reasoned later in his life, any duping of a credulous audience was possible.

Belbo's counterfeit Templar "Plan" brings together history and myth, fact and fiction, woven together using elaborate chains of association and allusion. It takes in the believers, and raises him to the status of master-interpreter.

'Secret society'

If you want to believe something badly enough, Eco's novels suggest, then by selective listening - by editing out the contrary evidence - you will hear what you want to hear. Nowhere is this more true currently than in the debate about global warming.

Last week, a last-minute global climate deal was struck at the Durban climate change conference. The conference ended with an agreement by all 194 countries to make a new global agreement covering every nation to come into effect by 2020.

Chris Huhne, the United Kingdom's climate change and energy secretary, said the Durban deal was "a significant step forward" because it set out a clear path to a new global and legally-binding treaty on cutting greenhouse gas emissions.

Image caption The two camps on either side of the climate change debate are poles apart

Difficult as such negotiations have proved, at successive international conferences, the continued commitment of almost all the world's nations surely points to the fact that the danger to our planet of high-level carbon emissions is a real one, on which there is widespread scientific and political agreement supported now by considerable bodies of evidence.

But according to the apparently growing band of climate change sceptics, this is a pernicious illusion. Partisan science, they claim, has taken hold of politicians and the media, and their message is being transmitted so loudly that it cannot be gainsaid.

The more determinedly the scientific community stands behind its global warming predictions, the more strongly the sceptics counter that there is no longer any "balance" to the argument and that their supposedly equally convincing views are being silenced.

Former president of the Royal Society Robert May is regularly denounced for allegedly announcing in 2006 that the case for global warming was so conclusively well proven that the BBC should stop giving climate change sceptics so much airtime in the interests of "balance".

Instead the climate sceptics have created an intricate web of their own associations and allusions, to produce their version of an alternative story which runs contrary to that of mainstream science.

What Umberto Eco's stories tell us is how comforting such quests can be. Faced with an uncertain future and declining prosperity, without religion for reassurance, what could be more comforting than to join a select band searching for the Holy Grail?

Image caption Sir David Attenborough's Frozen Planet series took viewers on a tour of the Arctic and Antarctic

The lesson I draw from all this, in the context of the arguments for and against climate change and global warming, is addressed to the climate scientists. Perhaps it is time to acknowledge that international scientific near consensus is not enough to allay the fears of those who feel left out of the whole debate.

Eco's illumination of the powerful way in which we can all hear clearly that part of the story that confirms our own convictions cuts both ways.

It is never a winning strategy to go on repeating dogmatically so-called "facts" that seem obvious to the already converted. To those who are fearful or simply unconvinced, this can sound like bullying. It can even be represented - and indeed has been by climate sceptics - as itself a conspiracy by a kind of "secret society", using selective, doctored evidence.

Graphs and pie charts have evidently failed to convince. Perhaps a more discursive approach which focuses on observable change backed up by scientific evidence may be more persuasive.

Maybe something more like a conversation is needed. That is surely why David Attenborough's recent plea that we recognise that global warming really is happening, at the close of his series of natural history programmes on the Arctic and Antarctic, had such authority:

"Polar animals are already reacting to the changes. The loss of sea ice in the north affects not just polar bears but the whole planet. When the ice vanishes, the dark sea-water that replaces it absorbs the sun's energy, so its temperature rises," he said.

"This is why the Arctic, a region the size of North America, is warming twice as fast as the rest of the planet. As a consequence, increasing amounts of meltwater are now flowing into the polar sea. The implications of that are hard to overstate."

Attenborough's audience have accompanied him on a personal voyage of discovery on his most recent visits to the polar regions. They have witnessed with him the changing patterns of life there, and shared his reactions to dramatic change that has taken place during his lifetime.

They may feel properly in a position to share his disturbing conclusions.