Moreover, as the latest IPCC report makes clear, careful studies have shown that, while extreme weather events such as floods, droughts and tropical storms, have always occurred, overall there has been no increase in either their frequency or their severity. That may, of course, be because there has so far been very little global warming indeed: the fear is the possible consequences of what is projected to lie ahead of us. And even in climate science, cause has to precede effect: it is impossible for future warming to affect events in the present.

Of course, it doesn't seem like that. Partly because of sensitivity to the climate change doctrine, and partly simply as a result of the explosion of global communications, we are far more aware of extreme weather events around the world than we used to be. And it is perfectly true that many more people are affected by extreme weather events than ever before. But that is simply because of the great growth in world population: there are many more people around. It is also true, as the insurance companies like to point out, that there has been a great increase in the damage caused by extreme weather events. But that is simply because, just as there are more people around, so there is more property around to be damaged.

The fact remains that the most careful empirical studies show that, so far at least, there has been no perceptible increase, globally, in either the number or the severity of extreme weather events. And, as a happy coda, these studies also show that, thanks to scientific and material progress, there has been a massive reduction, worldwide, in deaths from extreme weather events.

It is relevant to note at this point that there is an important distinction between science and scientists. I have the greatest respect for science, whose development has transformed the world for the better. But scientists are no better and no worse than anyone else. There are good scientists and there are bad scientists. Many scientists are outstanding people working long hours to produce important results. They must be frustrated that political activists then turn those results into propaganda. Yet they dare not speak out for fear of losing their funding.

Indeed, a case can be made for the proposition that today's climate science establishment is betraying science itself. During the period justly known as the Enlightenment, science achieved the breakthroughs which have so benefited us all by rejecting the claims of authority — which at that time largely meant the authority of the church — and adopting an overarching scepticism, insisting that our understanding of the external world must be based exclusively on observation and empirical investigation. Yet today all too many climate scientists, in particular in the UK, come close to claiming that they need to be respected as the voice of authority on the subject — the very claim that was once the province of the church.

If I have been critical of the latest IPCC report, let me add that it is many respects a significant improvement on its predecessors. It explicitly concedes, for example, that "climate change may be beneficial for moderate climate change" — and moderate climate change is all that it expects to see for the rest of this century — and that "Estimates for the aggregate economic impact of climate change are relatively small . . . For most economic sectors, the impact of climate change will be small relative to the impacts of other drivers." So much for the unique existential planetary threat.

What it conspicuously fails to do, however, is to make any assessment of the unequivocally adverse economic impact of the decarbonisation policy it continues to advocate, which (if implemented) would be far worse than any adverse impact from global warming.

Even here, however, the new report concedes for the first time that the most important response to the threat of climate change must be how mankind has always responded, throughout the ages: namely, intelligent adaptation. Indeed, the "impacts" section of the latest report is explicitly entitled "Impacts, Adaptation and Vulnerability". In previous IPCC reports adaptation was scarcely referred to at all, and then only dismissively.

This leads directly to the last of my four questions. To the extent that there is a problem, what should we, calmly and rationally, do about it?