AS of this week the days are getting longer again, the nights shorter. This week's great religious festival – no, I don't mean the celebration of Mammon and greed most of us have been indulging in – has been for the birth of the new sun.

AS of this week the days are getting longer again, the nights shorter. This week's great religious festival – no, I don't mean the celebration of Mammon and greed most of us have been indulging in – has been for the birth of the new sun.

And, as it happens, the new moon. Apollo and Diana are both waxing.

Of course, it will get colder before it gets warmer again. But not, perhaps, cold enough.

From the Book of Revelation to the Cold War and the A-bomb, from the ancient Maya to the disciples of David Icke, humankind has always had an obsession with ultimate extinction. It's part of the colossal arrogance of our species, the belief that our sin is strong enough to bring about the end of the world.

I don't believe it's literally true today, any more than it was in the days of Cain. But we now surely have the capacity, as a species, to wipe ourselves out. Or at least to make life a great deal less pleasant for those that may survive.

In the long run, America's self-indulgent use of oil and refusal to join the Kyoto accord on greenhouse gases may prove more devastating than all its war-mongering.

Is talk of global warming – or impending ice age – any more credible than the predictions of those star-gazers who expected the world to end last March? It is very difficult for a lay person like you or me to tell. I suspect it's pretty difficult for the boffins to be sure too.

Whatever the long-term prognosis, though, it seems global warming is a fact. Even if that glorious profusion of brilliant, colourful berries this autumn does turn out to have presaged a bleak winter.

Climate changes, of course. It always has. But no longer is it simply god-given. It is now the mechanism by which our sins may come back to punish us.

The man who made that connection – or at least brought it into the public domain – was Dr James Hansen of the Goddard Institute for Space Studies.

In 1988 he went before a US Senate energy committee to explain the dust-bowl conditions then afflicting much of the American Mid-West.

He told the senators: "With a high degree of confidence we could associate the warming with the greenhouse effect."

The comment received wide media coverage and provoked a debate among scientists that has largely come down on his side.

Now Dr Hansen is the co-author of a report that adds a new twist to the study of global warming.

It's not just the invisible "greenhouse gases" – principally carbon dioxide – and damage to the ozone layer of the atmosphere that are to blame.

Dr Hansen now estimates that a quarter of the heating effect is down to a much more visible product of human behaviour. Soot.

Now here is a substance we can all understand.

Dr Hansen's report defines it as "mainly black carbon, the dusty by-product of incomplete combustion of fossil fuels, plants and wood".

It's the stuff that clogs up your chimney, mucks up the back of your garage where you start the car, and gives your kids asthma.

It is produced in great quantities in Asia, where inefficient domestic fires can create the kind of smog we associate with Victorian London.

And it is poured out in massive concentrations in Britain, Europe and America by our great friend and enemy the internal combustion engine – lorries, cars and buses.

Soot, is seems, is twice as bad for the atmosphere as CO2 – and it doesn't get recycled by plantlife.

The problem is, it blackens the ice and snow that spreads out from both poles. And as we all know, while white surfaces reflect heat, black ones absorb it. So the sun's rays that used to reflect off pure white snow now warm up the sooty ice caps and gradually melt them.

Which is why the next few decades may see half of East Anglia become seabed. And why chunks of iceberg may break off the Arctic, cool and divert the Gulf Stream, and turn Britain into a new Siberia.

If you like a nice traditional horror story at Christmas, how's that one?

It's a lot more believable than the Four Horsemen of the Apocalypse. And every bit as scary.