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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Leave campaigners are doing down Britain's influence in Europe

As the third biggest country, Britain has huge clout in the EU.

Last week the Leave campaign's Priti Patel took to the airwaves to bang on about the perils of EU regulation, claiming it is doing untold damage to small businesses in the UK. Let's put aside for one minute the fact that eight in ten small firms actually want to stay in the EU because of the huge benefits it brings in terms of trade and investment. Or the fact that the EU has cut red tape by around a quarter in recent years and is committed to doing more. Because the really startling thing Patel said was that these rules come to us "without the British government having a say." That might be forgivable coming from an obscure backbencher or UKIP activist. But as a government minister, Priti Patel knows full well that the UK has a major influence over all EU legislation. Indeed, she sits round the table when EU laws are being agreed.

Don't take it from me, take it from Patel herself. Last August, in an official letter to the House of Lords on upcoming EU employment legislation, the minister boasted she had "worked closely with MEPs to influence the proposal and successfully protected and advanced our interests." And just a few months ago in February she told MPs that the government is engaging in EU negotiations "to ensure that the proposals reflect UK priorities." So either she's been duping the Parliament by exaggerating how much influence she has in Brussels. Or, as is perhaps more likely, she's trying to pull the wool over the British people's eyes and perpetuate a favourite myth of the eurosceptics: that the UK has no say over EU rules.

As the third biggest country, Britain has huge clout in Europe. We have the most votes in the EU Council alongside France, Germany and Italy, where we are on the winning side 87 per cent of the time. The UK also has a tenth of all MEPs and the chairs of three influential European Parliament committees (although admittedly UKIP and Tory sceptics do their best to turn their belief the UK has no influence in Europe into a self-fulfilling prophecy). UKIP MEPs aside, the Brits are widely respected by European counterparts for their common sense and expertise in areas like diplomacy, finance and defence. And to the horror of the French, it is English that has become the accepted lingua franca in the corridors of power in Brussels.

So it's no surprise that the UK has been the driving force behind some of the biggest developments in Europe in recent decades, including the creation of the single market and the enlargement of the EU to Eastern Europe. The UK has also led the way on scrapping mobile roaming charges from next year, and is now setting the agenda on EU proposals that will make it easier to trade online and to access online streaming services like BBC iPlayer or Netflix when travelling abroad. The irony is that the Europe of today which Eurosceptics love to hate is very much a British creation.

The Leave campaign like to deride anyone who warns of the risks of leaving the EU as "talking down Britain." But by denying the obvious, that the UK has a major role in shaping EU decisions, they are the ones guilty of doing our country down. It's time we stood up to their defeatist narrative and made the case for Britain's role in Europe. I am a proud patriot who wants the best for my country, and that is why like many I will be passionately making the case to remain in the EU. Now is not the time to leave, it's time to lead.