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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Five things we've learned from Labour conference

The party won't split, Corbynite divisions are growing and MPs have accepted Brexit. 

Labour won't split anytime soon

For months, in anticipation of Jeremy Corbyn’s re-election, the media had speculated about the possibility of a Labour split. But the party’s conference confirmed that MPs have no intention of pursuing this course (as I had long written). They are tribally loyal to Labour and fear that a split would prove electorally ruinous under first-past-the-post. Many still expect Theresa May to hold an early general election and are focused on retaining their seats.

Rather than splitting, Corbyn’s opponents will increase their level of internal organisation in a manner reminiscent of the left’s Socialist Campaign Group. The “shadow shadow cabinet” will assert itself through backbench policy committees and, potentially, a new body (such as the proposed “2020 group”). Their aim is to promote an alternative direction for Labour and to produce the ideas and organisation that future success would depend on.

MPs do not dismiss the possibility of a split if their “hand is forced” through a wave of deselections or if the left achieves permanent control of the party. But they expect Labour to fight the next election as a united force.

Neither the Corbynites nor the rebels have ultimate control 

Corbyn’s second landslide victory confirmed the left’s dominance among the membership. He increased his winning margin and triumphed in every section. But beyond this, the left’s position is far more tenuous.

The addition of Scottish and Welsh representatives to the National Executive Committee handed Corbyn’s opponents control of Labour’s ruling body. Any hope of radically reshaping the party’s rule book has ended.

For weeks, Corbyn’s allies have spoken of their desire to remove general secretary Iain McNicol and deputy leader Tom Watson. But the former is now safe in his position, while the latter has been strengthened by his rapturously received speech.

Were Corbyn to eventually resign or be defeated, another left candidate (such as John McDonnell) would struggle to make the ballot. Nominations from 15 per cent of MPs are required but just six per cent are committed Corbynites (though selection contests and seat losses could aid their cause). It’s for this reason that allies of the leader are pushing for the threshold to be reduced to five per cent. Unless they succeed, the hard-left’s dominance is from assured. Were an alternative candidate, such as Clive Lewis or Angela Rayner, to succeed it would only be by offering themselves as a softer alternative.

Corbynite divisions are intensifying 

The divide between Corbyn’s supporters and opponents has recently monopolised attention. But the conference showed why divisions among the former should be interrogated.

Shadow defence secretary Clive Lewis, an early Corbyn backer, was enraged when his speech was amended to exclude a line announcing that Labour’s pro-Trident stance would not be reversed. Though Lewis opposes renewal, he regards unilateralism as an obstacle to unifying the party around a left economic programme. The longer Corbyn remains leader, the greater the tension between pragmatism and radicalism will become. Lewis may have alienated CND but he has improved his standing among MPs, some of whom hail him as a bridge between the hard and soft left.

Elsewhere, the briefing against McDonnell by Corbyn allies, who suggested he was an obstacle to recruiting frontbenchers, showed how tensions between their respective teams will continue.

Labour has accepted Brexit

Ninety four per cent of Labour MPs backed the Remain campaign during the EU referendum. But by a similar margin, they have accepted the Leave vote. Jeremy Corbyn and John McDonnell, both long-standing eurosceptics, confirmed that they would not seek to prevent Brexit.

Owen Smith called for a referendum on the eventual deal during his leadership campaign. But with some exceptions, such as Angela Eagle, most of his backers have rejected the idea. Though 48 per cent of the electorate voted Remain, MPs emphasise that only 35 per cent of constituencies did. Some still fear an SNP-style surge for Ukip if Labour seeks to overturn the outcome.

The debate has moved to Britain’s future relationship with Europe, most notably the degree of free movement. For Labour, like Theresa May, Brexit means Brexit.

Corbyn will not condemn deselections 

The Labour leader could have won credit from MPs by unambiguously condemning deselection attempts. But repeatedly invited to do so, he refused. Corbyn instead defended local parties’ rights and stated that the “vast majority” of MPs had nothing to fear (a line hardly reassuring to those who do). Angela Eagle, Stella Creasy and Peter Kyle are among the rebels targeted by activists.

Corbyn can reasonably point out that the rules remain the same as under previous leaders. MPs who lose trigger ballots of their local branches face a full and open selection. But Labour’s intensified divisions mean deselection has become a far greater threat. MPs fear that Corbyn relishes the opportunity to remake the parliamentary party in his own images.  And some of the leader’s allies hope to ease the process by reviving mandatory reselection. Unless Corbyn changes his line, the issue will spark continual conflict. 

George Eaton is political editor of the New Statesman.