A lady came knocking on my door last week asking me sign my name to a petition about lowering carbon emissions. I really didn't want to.

The point is, I know there are too many planes flying to too many places, and too many cars, and too many exhaust pipes, and too many cow farts, but really there's only one problem: too many people. Which means, with the population at seven billion and doubling in the next 50 years, human semen is now the world's most dangerous weapon of mass destruction.

What's needed is a new George W Bush. Someone who will take things into their own hands and unilaterally plaster over-populated areas of the world with a germ-bomb that causes sterility.

Nope! I know. It won't work. Without a next generation there'd be no one around to do the work, unless it was a smart-germ that caused sterility in only half the population. Or if that idea is too offensive, why not a smart-germ that turns half the next generation gay? Or make them gay AND sterile, that should really do the trick.

(Oh dear! Is that a bit too Clarkson? Okay then - let them have their sperm back.)

Anyway, with someone knocking on my door asking me to sign something, I thought I should take a moment to decide what I really think about it all.

The International Energy Agency says that global warming will be beyond the point of no return in five years, and since there's nothing in the pipeline to reverse it before that time, it means we're doomed. And on that basis, I say let's enjoy ourselves while we can.

That, of course, is the sort of attitude that drives world-savers to despair. They can't understand how the majority of us can be so laissez-faire about what's happening. But how can we be anything else?

Ask anyone, do they care if, in 10 million years time, human beings no longer exist. You'll be hard pressed to find someone who says they do. Which is like the old joke, "Will you sleep with me for a million pounds?" "Okay, now we know what you are, let's fix a price."

So...

Now we know that people don't care if the human race dies out in ten million years, let's try and fix a period of time they feel more concerned about. My guess is, it's their children, and their children's children, and perhaps another lot too. For the hell of it, we could add a couple more generations, then double it. And it still comes to barely five hundred years.

Once that's over, perhaps it wouldn't be such a bad idea to have some sort of global-warming disaster to get rid of the over-population - kill off a few billion of us and stimulate a new burst of evolution. Let a new lot of top-dogs take over.

It'll be fun. Human beings can evolve into super-humans with huge brains and wispy limbs and voices like tinkling water. Or perhaps it will be the dolphins who get there first. Either way, any old-style humans who are still around will become the new lot's great apes. And when the new lot evolve upwards, humans will sink down to being their cats and dogs. And so on, till we're amoeba. I think that's all rather thrilling and wonderful. It's what the world should be about - moving on, developing, evolving. Not about us clinging on for dear life, endlessly trying to plop out one more generation of the same.

Now then - getting back to this carbon emission stuff...

Since anyone with an ounce of sense can see that the only answer is to cut down the number of people in the world - and since neither scientists nor politicians seem to have the ounce of sense that's required (or are just too scared to speak the truth and tell us that reducing the population is impossible) - all we can do is get on with our lives and hope things turn out okay.

I tried explaining this to the lady who was asking for signatures but she didn't seem to understand. And when I looked at her petition, I found it wasn't about carbon emissions after all, it was about stopping people in the neighbourhood burning rubbish in their gardens.

All part of the same thing, I suppose. Just a bit nearer home.