A FEW weeks ago I wrote that some emails had prompted me to reach for a copy of Mackay’s 1841 tome Popular Delusions and the Madness of Crowds.

It wasn’t just a rhetorical flourish – I really did, and nowI have ploughed through all 740 pages of it.

The witch craze is the most absurd: so many educated people with solid achievements in their professional lives appear to have fallen for the delusion that the air was thick with imps and demons in league with armies of witches, to whose malevolent spells any setback or accident might be attributed.

I wonder if “global warming” is a modern example of popular delusions and the madness of crowds.

But who are the deluded? Is it the scientists who have failed to take proper account of the history of our changing climate over millennia, or is it the sceptics who fail to take account of the evidence before our eyes?

Scores of people have been writing to me about this recently – prompted by the Navitus proposal for a giant wind farm off the Jurassic Coast. Are they victims of a popular delusion by insisting that the development is unnecessary? Is yet another example of the madness of crowds the furore that has been raised against the prospect of solving part of the problem by fracking rock sediments for natural gas? Or are the frackers the deluded ones, because it will perpetuate our reliance on carbon-based, climatedamaging energy sources?

For the present I am content to avoid the fundamental question that underlies all these issues, namely: “Is human activity responsible for climate change?” It seems to me that there is another perfectly sensible reason for reducing our reliance on carbon and for reducing our emissions: sound economics.

In every previous recession, recovery was assisted by cheap and falling energy prices. But the world has changed, this time the oil price has continued to rise and remains a significant restraint on growth.

The huge rise in demand from China and other Asian economies for energy and the fossil fuels that generate them will continue to drive prices up for these finite resources.

It is, therefore, a false choice between growth and going “green”. The real choice is between little growth, stifled by rising long-term prices of fossil fuels, and green growth created by escaping from our reliance on them.

So, even for those who have doubts about the causes of climate change, there are very prudent reasons for reducing our carbon emissions by fundamentally changing our reliance on fossil fuels to satisfy our energy needs.