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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A swimming pool and a bleeding toe put my medical competency in doubt

Doctors are used to contending with Google. Sometimes the search engine wins. 

The brutal heatwave affecting southern Europe this summer has become known among locals as “Lucifer”. Having just returned from Italy, I fully understand the nickname. An early excursion caused the beginnings of sunstroke, so we abandoned plans to explore the cultural heritage of the Amalfi region and strayed no further than five metres from the hotel pool for the rest of the week.

The children were delighted, particularly my 12-year-old stepdaughter, Gracie, who proceeded to spend hours at a time playing in the water. Towelling herself after one long session, she noticed something odd.

“What’s happened there?” she asked, holding her foot aloft in front of my face.

I inspected the proffered appendage: on the underside of her big toe was an oblong area of glistening red flesh that looked like a chunk of raw steak.

“Did you injure it?”

She shook her head. “It doesn’t hurt at all.”

I shrugged and said she must have grazed it. She wasn’t convinced, pointing out that she would remember if she had done that. She has great faith in plasters, though, and once it was dressed she forgot all about it. I dismissed it, too, assuming it was one of those things.

By the end of the next day, the pulp on the underside of all of her toes looked the same. As the doctor in the family, I felt under some pressure to come up with an explanation. I made up something about burns from the hot paving slabs around the pool. Gracie didn’t say as much, but her look suggested a dawning scepticism over my claims to hold a medical degree.

The next day, Gracie and her new-found holiday playmate, Eve, abruptly terminated a marathon piggy-in-the-middle session in the pool with Eve’s dad. “Our feet are bleeding,” they announced, somewhat incredulously. Sure enough, bright-red blood was flowing, apparently painlessly, from the bottoms of their big toes.

Doctors are used to contending with Google. Often, what patients discover on the internet causes them undue alarm, and our role is to provide context and reassurance. But not infrequently, people come across information that outstrips our knowledge. On my return from our room with fresh supplies of plasters, my wife looked up from her sun lounger with an air of quiet amusement.

“It’s called ‘pool toe’,” she said, handing me her iPhone. The page she had tracked down described the girls’ situation exactly: friction burns, most commonly seen in children, caused by repetitive hopping about on the abrasive floors of swimming pools. Doctors practising in hot countries must see it all the time. I doubt it presents often to British GPs.

I remained puzzled about the lack of pain. The injuries looked bad, but neither Gracie nor Eve was particularly bothered. Here the internet drew a blank, but I suspect it has to do with the “pruning” of our skin that we’re all familiar with after a soak in the bath. This only occurs over the pulps of our fingers and toes. It was once thought to be caused by water diffusing into skin cells, making them swell, but the truth is far more fascinating.

The wrinkling is an active process, triggered by immersion, in which the blood supply to the pulp regions is switched off, causing the skin there to shrink and pucker. This creates the biological equivalent of tyre treads on our fingers and toes and markedly improves our grip – of great evolutionary advantage when grasping slippery fish in a river, or if trying to maintain balance on slick wet rocks.

The flip side of this is much greater friction, leading to abrasion of the skin through repeated micro-trauma. And the lack of blood flow causes nerves to shut down, depriving us of the pain that would otherwise alert us to the ongoing tissue damage. An adaptation that helped our ancestors hunt in rivers proves considerably less use on a modern summer holiday.

I may not have seen much of the local heritage, but the trip to Italy taught me something new all the same. 

This article first appeared in the 17 August 2017 issue of the New Statesman, Trump goes nuclear