I wonder when people last got widely and publicly ridiculed for not believing in God: probably not for several hundred years.

Nowadays, you'd get a slightly odd look for doing the opposite and expressly stating your faith. But, if you really want to know what it's like to be a 16th-century heretic, try saying you're a bit sceptical about man-made global warming.

Temperatures do seem to have gone up a little, even though environmentalists acknowledge that we might be in for a cool spell now. And we've certainly had our fair share of tsunamis, hurricanes and typhoons recently. Still, no one has convincingly proved that all this is definitely man's fault. Try saying that in polite circles and it's like saying you're partial to roasted babies.

I understand people disagreeing with global warming sceptics, but not the jeering, ridiculing way they do it. I'm not sure I'm right; they're convinced I'm wrong. They're convinced, too, that they have the moral high ground, that all sceptics are sworn enemies of nature, flowers and puppy dogs.

Environmentalism is the new secular faith - school prayer for liberals, as an American philosopher put it. The faith is a strict one. You're not allowed to join if you think that it's sensible to keep an eye on the environment but don't think that man is to blame for changes in world temperature.

You must believe in the full package. If you do, you are blessed, free from sin and allowed the pious smugness you find in the worst sort of religious believers. It's not enough to believe in these things yourself; you must condemn others for not sharing your belief.

The latest carbon credits scheme - published in a parliamentary committee report - is squarely on the side of the believers. The idea is that everyone gets an annual carbon ration to spend on fuel and energy bills and, if you want to overspend, you buy credits from low carbon emitters.

It's just like the medieval trade in indulgences, where remission for sins was granted by the Church once the sinner confessed and received absolution. By the late Middle Ages, the system had grown corrupt, with professional pardoners selling indulgences by the bucketload.

The medieval market in indulgences ended with the Reformation. You can imagine the outcome of this market in modern sin. Oceans of sackcloth-and-ashes piety from those who underspend their carbon credit, and badly informed abuse for people who like flying abroad on holiday.  Read rest...