Climate science is by nature uncertain

Adam Corner, guardian.co.uk 25 Jun 09;

For climate sceptics, the mere presence of uncertainty is reason enough to doubt. But doubt is not an enemy – it is the stimulus that drives science forward

It seems the one thing climate change sceptics are certain of is uncertainty, in particular how uncertainty in the predictions of climate models fatally undermines their legitimacy.

So the recent revelation of the UK government's projections of global warming through to 2080 was met, predictably, with some cynicism by the deniers. While some commentators used the detailed projections about possible future UK climate scenarios to underscore why we must take strong action on climate change, the response of climate sceptics was to say that the error bars in the projections made them worthless.

Never mind that the level of uncertainty about mean temperature increase, sea level rise and seasonal rainfall was dealt with in painstaking and meticulous detail in the report. For some, the mere presence of uncertainty was reason enough to doubt. But uncertainty is not an enemy of science that must be conquered – it is the stimulus that drives science forward. As in economic forecasts, medical diagnoses, and policy making, uncertainty runs through climate science like the lettering in sticks of rock.

The good news is that scientists are particularly adept at acknowledging, identifying and modelling it. The Met Office team responsible for the climate projections managed to systematically indicate what they did know, what they didn't know and how confident they were about these judgments. If there's one group of people who have thought long and hard about uncertainty, its climate scientists. But Irene Lorenzoni and her colleagues at the University of East Anglia have shown that people frequently view uncertainty as a reason for inaction on climate change.

Such is the level of scepticism in some quarters that climate scientists are constantly required to apologise for what they don't know, rather than encouraged to communicate what they do.

But uncertainty is not the same as ignorance – which is why the labelling of GM food became mandatory in 2004. The Food Standards Agency did not demand certainty before taking action, although the uncertainty surrounding the risks of genetic modification is far greater than the considered consensus of climate science.

One reason that so much attention is given to the uncertainty associated with climate models is that they form the basis of important and costly policy decisions. But the "precautionary principle" is a well-established method of policy making when uncertainty prevails, on the basis that it is better to be safe than sorry. Could it be that climate sceptics' obsession with uncertainty is simply an unwillingness to accept the consequences of the climate changing – that their lifestyles will have to change as well?

The UK climate projections are not a weather forecast for 3 July 2078. They are a set of scientifically rigorous probabilistic assessments of what the UK climate might be like in, say, 50 years time. But the writers of the report seemed to feel compelled to get their counter-arguments in early. Of course, it is absolutely essential that all uncertainties in climate models are made clear. But it's odd reading a scientific report where the caveats come before the take-home message.

There is one crucial uncertainty, however, that cannot be captured in any climate model: the extent to which action is taken to cut the emissions of greenhouse gases. The irony of the debate surrounding what we can and can't infer from climate models is that they sketch out possible, not inevitable futures. By giving us some idea of what lies ahead, they furnish us with a critical opportunity to change course. Rather than procrastinating about uncertainty – an inescapable fact of life – we should be taking the opportunity to get serious about climate change, and prove the climate models wrong.

• Dr Adam Corner is in the understanding risk research group at Cardiff University