How do you price the death of the world?

Climate change is hard to account for.

Grist's David Roberts writes about the distinction between climate change and other environmental problems:

The first difference is that carbon dioxide is not like other pollutants… The typical climate-policy targets that get thrown around — reducing emission rates by 80 percent by 2050, for example — are relatively meaningless. They focus on the rate of flow from the faucet. But that’s not what matters. What matters is the amount in the tub. If the tub fills up enough, global average temperature will rise more than 2 degrees Celsius and we’ll be in trouble. Avoiding that — staying within our “carbon budget” — is the name of the game.

The second difference is that climate change is irreversible.

Roberts cites a 2009 paper from Nature, "among many others":

The climate change that takes place due to increases in carbon dioxide concentration is largely irreversible for 1,000 years after emissions stop. Following cessation of emissions, removal of atmospheric carbon dioxide decreases radiative forcing, but is largely compensated by slower loss of heat to the ocean, so that atmospheric temperatures do not drop significantly for at least 1,000 years.

Climate change is notoriously tricky to deal with in standard economic terms. Part of it is that, to any normal person, something which is irreversible for 1,000 years sounds at least ten times worse than something which is irreversible for 100 years, if not even worse still.

Economically, though, the two are essentially the same. "Present value" is an economic concept dealing with the fact that money in the future is worth less than money now – because you can always invest money now and have more money in the future. Of course, that assumes long-term growth, which, if we're talking about world-changing events like anthropogenic climate change, might not be a safe assumption.

But the end result of the calculations is that nearly any cost beyond a hundred years into the future isn't worth spending money today to avoid. The intuitive conclusion – that it's worth fighting climate change harder if it will last for a millennium than a century – isn't the case. Assuming growth.

But there are even bigger problems for climate change than that. The vast majority of economic responses to it require calculating a "likely cost", and then applying that to the measures proposed to combat it. So, for example, a properly implemented carbon tax requires a calculation of the damage one tonne of CO2 does to the environment, in order to accurately price in the negative externalities.

Unfortunately, conventional ways of pricing risk rather fall over when considering something like climate change, because it carries a non-zero risk of existential threat. That is, there are proposed mechanisms whereby "runaway climate change" could present a civilisation-ending threat.

How do you price the end of civilisation? One option is to look at the value of everything in the world. It would be quite an accounting task, and one faced by the UK government last year when they had to put a price on Stonehenge to fulfil new bookkeeping requirements. The American government puts the value of the entirety of the US at $110trn, so it seems likely that the value of all the world's civilisations is well into 16 figures.

That's high, but it's countable. The real issue comes when you look at an alternative way of measuring the cost of risk, which is the amount you would pay to prevent it. Presumably, there is no sum which would not be worth spending to prevent the end of civilisation. Any cost would be less than the destruction of everything.

By that measure, then, the damage caused by an existential threat is infinite. But the problem with infinite quantities is that they don't work very well in conventional mathematics. Back to the normal risk accounting: you typically multiply the damage you are risking with the chance it will happen. So we are happy to suffer high risk of low damage – like groping for a glass of water at midnight with the lights off – or low risk of high damage – like driving a car – but not high risk of high damage – like driving a car at midnight with the lights off.

But infinity multiplied by anything other than zero is still infinity. Conventional risk assessment simply falls apart when confronted with something the magnitude of the worst possibilities of climate change.

Note too that it doesn't require the risk to be large. I think the risks of climate change are greater than most, but I also think it's extraordinarily unlikely that it actually would result in the end of civilisation. But can we rule it out with certainty?

The best way to look at it is to compare it to our every day lives. Thousands of people are killed crossing the road every day. To do so carries a non-negligible personal existential threat – that is, you might die. Yet I see people dodging traffic to get to work 30 seconds earlier every day, which suggests that, instinctively, we don't treat the risk of death with as much weight as we perhaps should.

But I think theres a different motivator at work. We know death is bad, and that it's worth doing a lot to try and avoid it; but we also know death can come from any corner. And the same is true of fighting existential threats to civilisation. If we could spend ludicrous sums to eliminate them all, it might be worth it; but who's to say we won't prevent climate change, only to die from an asteroid hit? Or cap our future development by not experimenting with nanotech, only for an angry AI to kill us in our sleep?

Climate change could be very, very bad indeed. But making the important choices about the trade-offs we should make to fight it are hard because, not despite, its seriousness.

Photograph: Getty Images.

Alex Hern is a technology reporter for the Guardian. He was formerly staff writer at the New Statesman. You should follow Alex on Twitter.

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The dog at the end of the lead may be small, but in fact what I’m walking is a hound of love

There is a new, hairy face in the Hovel.

There is a new, hairy face in the Hovel. I seem to have become a temporary co-owner of an enthusiastic Chorkie. A Chorkie, in case you’re not quite up to speed with your canine crossbreeds, is a mixture of a chihuahua and a Yorkshire Terrier, and while my friend K— busies herself elsewhere I am looking after this hound.

This falls squarely into the category of Things I Never Thought I’d Do. I’m a cat person, taking my cue from their idleness, cruelty and beauty. Dogs, with their loyalty, their enthusiasm and their barking, are all a little too much for me, even after the first drink of the day. But the dog is here, and I am in loco parentis, and it is up to me to make sure that she is looked after and entertained, and that there is no repetition of the unfortunate accident that occurred outside my housemate’s room, and which needed several tissues and a little poo baggie to make good.

As it is, the dog thinks I am the bee’s knees. To give you an idea of how beeskneesian it finds me, it is licking my feet as I write. “All right,” I feel like saying to her, “you don’t have to go that far.”

But it’s quite nice to be worshipped like this, I have decided. She has also fallen in love with the Hovel, and literally writhes with delight at the stinky cushions on the sofa. Named after Trude Fleischmann, the lesbian erotic photographer of the Twenties, Thirties and Forties, she has decided, with admirable open-mindedness, that I am the Leader of the Pack. When I take the lead, K— gets a little vexed.

“She’s walking on a loose lead, with you,” K— says. “She never does that when I’m walking her.” I don’t even know what that means, until I have a think and work it out.

“She’s also walking to heel with you,” K— adds, and once again I have to join a couple of mental dots before the mists part. It would appear that when it comes to dogs, I have a natural competence and authority, qualities I had never, not even in my most deranged flights of self-love, considered myself to possess in any measurable quantity at all.

And golly, does having a dog change the relationship the British urban flâneur has with the rest of society. The British, especially those living south of Watford, and above all those in London, do not recognise other people’s existence unless they want to buy something off them or stop them standing on the left of the sodding escalator, you idiot. This all changes when you have a dog with you. You are now fair game for any dog-fancier to come up to you and ask the most personal questions about the dog’s history and genealogy. They don’t even have to have a dog of their own; but if you do, you are obliged by law to stop and exchange dog facts.

My knowledge of dog facts is scant, extending not much further beyond them having a leg at each corner and chasing squirrels, so I leave the talking to K—, who, being a friendly sort who could probably talk dog all day long if pressed, is quite happy to do that. I look meanwhile in a kind of blank wonder at whichever brand of dog we’ve just encountered, and marvel not only at the incredible diversity of dog that abounds in the world, but at a realisation that had hitherto escaped me: almost half of London seems to have one.

And here’s the really interesting thing. When I have the leash, the city looks at me another way. And, specifically, the young women of the city. Having reached the age when one ceases to be visible to any member of the opposite sex under 30, I find, all of a sudden, that I exist again. Women of improbable beauty look at Trude, who looks far more Yorkie than chihuahua, apart from when she does that thing with the ears, and then look at me, and smile unguardedly and unironically, signalling to me that they have decided I am a Good Thing and would, were their schedules not preventing them, like to chat and get to know me and the dog a bit better.

I wonder at first if I am imagining this. I mention it to K—.

“Oh yes,” she says, “it’s a thing. My friend P-J regularly borrows her when he wants to get laid. He reckons he’s had about 12 shags thanks to her in the last six months. The problems only arise when they come back again and notice the dog isn’t there.”

I do the maths. Twelve in six months! That’s one a fortnight. An idea begins to form in my mind. I suppose you don’t have to be a rocket scientist to work out what it is. But no. I couldn’t. Could I?

Nicholas Lezard is a literary critic for the Guardian and also writes for the Independent. He writes the Down and Out in London column for the New Statesman.

This article first appeared in the 28 April 2016 issue of the New Statesman, The new fascism