A Five Sigma Event

This is the continent of Antarctica. You can see that the land mass is surrounded, especially in winter, by an expanse of sea ice of comparable extent. It is impossible in winter for ships to push through this sea ice, even if said ship has ice-breaking capabilities. Access, then, is by air only. Antarctica is not a hospitable place.

Late in summer, suitably ice-strengthened ships can make it to the land mass in certain places. Early this century, I travelled on board such a ship – a Russian vessel, named after the poet, Marina Tsvetaeva – into the northern reaches of the Ross Ice Shelf. Together with the other paying passengers, I was able to get out and tread the rocky terrain. We hiked to such places as Shackleton’s hut, and to the grave of Nicolai Hanson, the first person ever to die on this frigid continent. He died there in 1899.

My experience, unforgettable of course, at times felt dangerous. But I’m glad I did it. All of it. My overall experience left me chock full of indelible memories.

But why do I bother to mention my experiences in Antarctica, significant though they may be to me? Why do I mention the sea ice through which we, at various times, had to push? Plenty of people, these days visit this remote continent whose permanent residents comprise mainly penguins, leopard seals, orcas, and the like. So what’s the big deal?

I’ll tell you what the deal is. According to the scientists that study these things, the winter sea ice this year has experienced a five sigma event.

Sigma is the eighteenth letter in the Greek alphabet. Scientists and statisticians use its lower case form as a measure – called the standard deviation – of the likelihood of an event occurring. Absolute certainty in science is unattainable. But if an event rates five sigmas or higher, the likelihood of it occurring is near zero, i.e. less than the fraction 0.0000003 (or 1 in 3.5 million). The more sigmas the event rates, the more unlikely the event is.

The recent film Oppenheimer postulates a conversation between General Leslie Groves and the eponymous J Robert O, regarding the possibility, then doing the rounds, that if the proposed bomb test at Alamogordo went ahead, it would set off a chain reaction in the atmosphere that would destroy all life on earth.

When Groves asks Oppenheimer to confirm this alarming rumour, Oppenheimer tries to reassure him by saying the chances of this are ‘near zero’. Realizing his answer has done little to reassure Groves, he then asks ‘What do you want from theory alone?’, to which Groves replies ‘Zero would be nice.’

That’s an important difference between a scientist and a lay person. The zero that Groves wants is impossible. The best Oppenheimer can offer is something in the order of a five sigma rating.

What if a verified five sigma event, despite its having ‘near zero’ likelihood, is found to have actually occurred? Almost certainly it means that some very significant but underlying effect has not been taken into account.

Consider an example from particle physics. When data from experiments at CERN’s large hadron collider was suggestive of a five sigma event, physicists concluded that a massive boson not previously seen (an 800-pound gorilla, no less) must necessarily exist. Peter Higgs had predicted the existence of this boson decades earlier on the basis of theory alone. But now the experimental evidence was in, taking the form of a telltale five sigma event. Shortly before he died, Higgs’ judgment was vindicated, and the boson was named after him.

So let’s get back to Antarctica and its sea ice. The deficit in winter sea ice this year is a five sigma event. That’s the science. So where is the 800-pound gorilla to be found?

The most obvious candidate, perhaps the only candidate, is climate change a.k.a. global warming. The evidence from winter sea ice in Antarctica in 2023 is that there is a 1 in 3.5 million chance that global warming doesn’t exist. It’s odds on that it does exist.

I wouldn’t fancy a bet against those sort of odds.

And so what? you might ask. Let the Antarctic sea ice melt a little quicker if it must. What does that matter to people living in more northern climes?

This is what matters.

Sea ice, being white in colour, reflects something like 85-90% of sunlight falling on it. Ocean water, on the other hand, is dark, and reflects only about 10%. So, when global warming impinges on this system, it …

… melts more sea ice, decreasing the amount of sunlight reflected, thereby contributing to global warming, which …

… melts more sea ice, decreasing the amount of sunlight reflected, thereby contributing to global warming, which …

… melts more sea ice, decreasing the amount of sunlight reflected, thereby contributing to global warming, which …

Do you see which way things are trending, and where things will end?

The beast you have here is known as a positive feedback loop. Such beasts are typical of explosive chain reactions and other such catastrophic events. The pace of climate change, subject to positive feedback, will in no time at all become exponential. That spells doom for all of us, no matter which clime we inhabit.

The worry is that more and more five sigma events are cropping up around the globe, often associated with positive feedback loops.

We ignore the science at our peril. Some have decided to bash these pesky scientists. They don’t like the message they deliver, so they’ll shoot the messenger.

But such people can deny the truth till kingdom come, aggressively if that’s their wont, until finally that truth catches up to them, to the rest of humanity, and to all living creatures on the planet. It’s looking as if only those creatures currently approaching the end of their natural life spans, or those who might perchance come face to face with unnatural deaths in their immediate future, will be spared the horrors of a world disintegrating before their very eyes, a world riven by a succession of five sigma events and positive feedback loops.

We could intervene, of course. That’s always been an option for us. But is there time left? And do we have the will?