Things are so complicated it's a wonder anyone knows what's going on. But then, no one does. No one can. There's too much to know. Not that Lord Turner of Ecchinswell put it like that. He's climate change. It's his job to project omniscience in the face of the unknowable.

He told the Environmental Audit Committee that reducing emissions by 80 per cent will lead to a 50-50 probability of keeping world temperature increases below C. How wonderfully authoritative that sounds. What certainty it offers, by specifying the degree of uncertainty. What precision. What exactitude.

At the cost of several trillion dollars, we will achieve a global goal that sceptics assume is unachievable. This amazing effort may or may not have the predicted effect. Maybe it will, maybe it won't. Is that a little casual? By the same token, he told us that with the 80 per cent reduction, the chance of world temperatures increasing by 4C is just 1 per cent.

But we live in a world where temperature claims on both sides are supported by conflicting statistics and where the economic cycle makes a mockery of politicians' predictions – but here is Lord Turner applying his definitive probabilities to a multi-trillion-dollar bet and assumes he will carry the country with him.

He also said that if we wanted to increase the probability to 99 per cent we would have to start de-industrialising immediately. But then if we did de-industrialise and we still breached the C he would rightfully say: "I did warn you there was one chance in a hundred it would happen."

These unknowables are matched by the more ordinary mysteries of administrative life.

What's the likelihood of getting three nuclear power stations through planning and construction by 2020. Is that going to happen? "It is... absolutely... not impossible," Lord Turner said. He didn't specify the improbability.

Now, as you're a well-informed climate change specialist you can almost certainly explain the difference between a carbon credit and a carbon offset and why a credit is better than an offset. But did you know that your virtuously-procured EU Emissions Trading credits contain offsets? Ah ha!

But even if you're expert in the field to the extent of being on the EAC you might be confused about whether new power stations really had to be clean-coal-compliant. You thought there was wriggle room? No the policy changed in February.

And even if you're the minister you might not know whether some target for 2020 was 2 per cent or 20 per cent – the ministerial preference. It was 2 per cent in the minister's document but it's certain there is a probability factor that everyone was right.

simoncarr@sketch.sc