To be a sceptic is a difficult and dangerous business. To be what the philosopher, David Hume, called a “mitigated”, or moderate, sceptic is, in addition, deeply frustrating. In the first case, sceptics are seen as enemies of ”religion”; in the second, the moderate sceptic is constantly misunderstood, because one is dealing with carefully-modulated degrees of questioning and doubt that do not conform easily to the modern world of sound bites, shallow interviews, and pressure-group action. The media inevitably favour the religious fanatic who can encapsulate into a single sound bite simple articles of unquestioned faith that mesh readily with the prevailing public mood, which they themselves so often – too often – share.

In the UK, ”global warming” is now a faith. We must not underestimate this fact. To be a “speculative atheist” – again employing Hume – is to place oneself on the outside of liberal society. You will be interviewed as a curiosity, if at all. You will also be attacked ad hominem. The aim will be to make you a leper, an untouchable. Some polite American scientists, when they are interviewed on, say, BBC Radio 4, are shocked by the vitriol they encounter if they dare to raise complexities and queries about the science, or even about appropriate action in relation to the perceived threat of ”global warming”. They have forgotten that, in the UK, the ”science” is legitimised by the popular myth, not the other way round. This is something that even our august Royal Society has failed to grasp. Too many of us believe that we are making an independent scientific assessment, when, in reality, we have subsumed vital Humean scepticism to the demands of the faith.

But to be a “mitigated” sceptic – like me – is even more problematic. The “mitigated” sceptic has first to distinguish ”global warming” from ”climate change”. Secondly, ”climate change” itself has to be broken down into three component and separate questions: “Is climate changing and in what direction?” “Are humans influencing climate change and to what degree?” And: “Are humans able to manage climate change predictably by adjusting one or two variables, or factors, out of the thousands involved?” Imagine trying to unravel these threads in the shoddy warp and weft of a three minute radio interview, or a five minute television debate between three people. There is no air space for the “just reasoner”. Yet, as Hume was at pains to stress, when we are shown the “infirmities” of human understanding, we should naturally acknowledge “… a degree of doubt and caution, and modesty, which, in all kinds of scrutiny, ought ever to accompany a just reasoner.”

What is more deeply depressing, however, is the failure of the media, not the failure of the politicians, nor of the scientists. A critical media is vital for a functioning democracy. The media, nevertheless, can become dangerous when it ”crusades” uncritically, siding too readily with the establishment and government of the day. In such circumstances, the debate never achieves the depths of “just reasoning”, but becomes ensnared by the slogans of ”the faithful”, or worse, of the spin doctor and activist.

The fundamental question in relation to ”global warming” is: “Can humans manipulate climate predictably?” Putting this more scientifically: “Will cutting carbon dioxide emissions at the margin produce a linear, predictable change in climate?”

The “mitigated” sceptic has to answer “No”. In so complex a coupled, non-linear, chaotic system as climate, not doing something at the margins is as unpredictable as doing something. Surely, this is what the Royal Society should be admitting? This is the cautious science; the rest is dogma. And what precisely is a “better” climate? “Doing something” might inadvertently lead to “worse”.

We are thus crying out for a media that will have the bravery to seek “just reason”. On climate change, the British public deserves a richer and more nuanced debate.

I must thus remain the “mitigated” sceptic, despite the tenor of the times. My scepticism is not extreme. It is not the scepticism of pure relativism. Rather, it confronts instead what can be done about climate change that will work. At present, this fundamental question is lost in the clamour “to do something at all costs” and to damn those who doubt we can.

Philip Stott is Professor Emeritus of biogeography at the University of London. This article was first published on his website Envirospin and is republished here by permission.