TEOTWAWKI II: Climate Change, Ecotastrophe

Hello and welcome to this TEOTWAWKI special of Physical Attraction.

I need to do a little housekeeping to explain the next few episodes of TEOTWAWKI. What I’m going to be talking about is various different kinds of ecological or environmental catastrophe — and, under this big umbrella, we have number 2 on my list of potential apocalypses.

In many ways, what we’re doing to the environment should be looked at holistically. You can’t make too many arbitrary dividing lines that make sense. So, for example: deforestation contributes to habitat loss, which can cause species to go extinct. But, as trees absorb carbon dioxide, deforestation — and changing land use in general — contributes to carbon emissions by removing a sink of carbon. This has an impact on climate change. And climate change — the rapid kind that we’re engaging in — also destroys habitats and puts incredible strain on ecosystems.

But I know, given how complex and important this issue is, I’m going to spend a very long time describing it. So in a way, I’m making the same kind of compromise that historians have to make all of the time. Discretising history — splitting it up into little chunks — is an arbitrary choice that we make. Dividing lines are rarely as easy to draw as we’d like them to be. You can’t really understand what’s going on in the Roman Empire without understanding the Roman Republic, and the Greek civilizations before that, and so on… As Mike Duncan put it, “it really is all the same big story, but we can’t make podcasts called ‘The History of the Human Race, 2 million years ago to the present’”. Not that people haven’t tried.

So, for the sake of clarity, I’m going to split the ecological and environmental catastrophe into two parts. The first will focus on pollution, species extinction, and scarcity of resources — what you might call a general ecological collapse. The second part is going to focus on perhaps the most famous environmental problem we have: climate change.

As is always the case, I can only possibly begin to scratch the surface of the topics that I’m talking about here. Naturally this show is limited by my own knowledge and ability to research things — which means I can quote unquote cover the whole field of epidemiology in an hour or so. I don’t know what I’m missing. But climate change is something I know a bit more about, and so inevitably that episode is going to be a pretty mammoth offering. Equally, there are crises in the field of biodiversity that I just won’t be aware of, because it’s not my field. If you know more: get in touch and I can feature this in a future episode, or maybe even interview you on the show.

So although I’ve made this arbitrary split just to make things manageable, you should bear in mind that these things are completely interrelated. Climate change has impacts on biodiversity and habitat loss; pollution interplays with climate change. (For example, one of the reasons that climate change has proved so difficult to measure is the amount of ‘aerosol pollution’ that is currently in the atmosphere — this includes things like nitrous oxide and sulfur dioxide that go into making up ‘smog’, the effects of which can be complicated in the atmosphere. Scientists actually think that the net effect of the ‘smog’ is to block out the Sun and cool the Earth down, which means that — in a smogless world — we would have had more warming due to CO2 than we’ve actually observed.) So everything is interlinked, and often in ways we barely even appreciate — or don’t realize until it’s already too late. It’s good to keep this in mind.

I think the overarching theme is going to be sustainability. Because this is what it all comes down to: the way we live now is not sustainable. Whether it’s extracting finite resources from the Earth with no way to replenish them; whether it’s polluting the landscape and killing off the other species we share the Earth with; whether it’s carbon emissions that will, if unchecked, eventually lead to climate catastrophe — it all comes down to the fact that we can’t keep doing what we’re doing. We need to be smarter, cleaner, greener; or we will risk our survival.

Of course, the irony is that this is all just a consequence of why we’re so dominant as a species. Homo sapiens is, in some sense, a victim of its own success. After all; what’s so special about us? We can’t run faster, jump further; no scary claws or teeth; in a fair fight, compared to many top predators in the animal kingdom, we’d lose every time. But it’s not a fair fight. We are smart enough to understand and change the rules of the game.

Have you ever had that sudden moment of revelation? Perhaps you’re sitting in your room, or staring out of the window of a bus absent-mindedly…. It’s not even really a revelation, because that implies something is being revealed to you; this is just a reminder, a remembering, a recollection. You suddenly realize that nearly everything around you has been put there by humans. It’s all been pulled from the Earth, from the bowels and the rocks below or from the oceans or from the animals — it’s undergone some energy-intensive manufacturing process, usually — and then it’s been transported to you? The roads the bus travels on, the seat underneath you, the stylish artifice of your clothes, the machine in your hand that dispenses blue days and black nights… All of these things pulled from the Earth. Some of them containing a wide and bewildering array of substances that you might not even have heard of. Many of them made and manufactured in places you will never go, by people you will never see, with raw materials extracted from mines none of us have heard of.

It’s crazy when you stop to think about it. For the last billion or so years, the silicon in the chips of the computer I’m using to type this was happy being sand, or rocky ore somewhere; and now, in the last tiny fraction of its life, humans have cruelly snatched it away, transported it across the world several times, and tricked it into thinking.

Let’s say you spend the day at home: a lazy Sunday. It’s perfectly possible — probable, even — that most of what you touch anything that would exist without humans. Everything is either completely artificial — or natural things that we’ve bent and twisted and harnessed into shape. It’s all artificial. Birds can make nests and bees can make hives to protect themselves from the world, but no creature other than humans has engaged in world-altering — geo-engineering — on such a massive scale, to suit our needs, to protect us, to fulfil our desires. And when I think about how strange it is — that we have, over many years, shaped so much of the world to suit our needs — I’m afraid about what the consequences might be. And I’m not convinced that in a hundred, in a thousand years, we’ll still be able to live like this: throwing away plastic bags, burning fossil fuels for power, eating whatever we want: with so many of us living so profligately from the fruits of the Earth.

Equally, we depend on this process. Most of us are no longer even close to self-sufficient; if the food stops being delivered to the supermarkets, we’d struggle to survive. For all our genius, for all our confidence and hubris, we are living with two life-support systems, twin high-maintenance machines: the artificial one that we have created, and the natural one that feeds it. But can they sustain each other?

The impacts of our massive experiment to try to shape the world to be more comfortable for us — they’re all around us. Take the biodiversity crisis. We are currently in a mass extinction:

Every day biodiversity is being lost at up to 1,000 times the natural rate. The extinction of individual species, but also habitat destruction, land conversion for agriculture and development, climate change, pollution and the spread of invasive species, often introduced into places where they aren’t naturally occurring by humans, are only some of the threats responsible for today’s crisis.

With the current biodiversity loss, we are witnessing the greatest extinction crisis since dinosaurs disappeared from our planet 65 million years ago. Not only are these extinctions irreversible, but they also pose a serious threat to our health and wellbeing.


  • Coral reefs provide food, storm protection, jobs, recreation and other income sources for more than 500 million people worldwide yet 70% of coral reefs are threatened or destroyed.
  • 17,936 species out of 52,017 assessed so far are threatened with extinction.
  • Of the world’s 5,490 mammals, 78 are Extinct or Extinct in the Wild, with 188 Critically Endangered, 450 Endangered and 492 Vulnerable.
  • 1,895 of the planet’s 6,285 amphibians are in danger of extinction, making them one of the most threatened groups of species known to date.

As many as 30–50% of all species could be headed towards extinction by the middle of the century. And this isn’t a natural occurrence. In fact, 99 percent of currently threatened species are at risk from human activities. It’s true that species have always gone extinct in the past before — just like the climate has always changed — but over time periods of thousands of years: or else due to transient causes like volcanic eruptions or asteroid strikes that give biodiversity time to flourish again.

Species that you’d never expect can be threatened and hunted to extinction by humans — we’re not just talking about rare insects that . An example I always think of — one that makes you utterly incredulous, really — is the passenger pigeon.

They are called passenger pigeons due to the massive flights they used to take across the sky, and there used to be billions of them in North America. In 1914, the last passenger pigeon died. From having been one of the most abundant species on the planet, they are now extinct.

Quoting from the excellent centre for biodiversity website, with their hard-to-argue with motto “life is good”

“A flock of passenger pigeons reported in Ontario in 1866 was described as being a mile wide and 300 miles long and taking 14 hours to pass overhead.

And though their species enjoyed a long, long life before they met up with modern homo sapiens, that contact was all too brief. These remarkable birds, with their iridescent wings, fiery-red feet, sparking scarlet eyes and unmistakably deafening calls, passed from the Earth 99 years ago.

In the 19th century, the passenger pigeon may have been the most abundant bird in the entire world, with a population believed to have approached 4 billion individuals. As they rested in their forest habitat, roosting flocks overburdened strong trees to such an extent that some birds had to settle upon their flockmates’ backs to get some sleep — and thick branches were known to snap under the birds’ weight.

Flocks in flight were a spectacle without parallel, enormous masses of birds taking on multiple shapes as they twisted and undulated across the firmament. Famed naturalist John James Audubon described these flocks delightfully — and dramatically — as blackening the skies “as by an eclipse.”

One of the most social land birds, the passenger pigeon also displayed unique, charming behaviors, living in colonies stretching over hundreds of square miles, practicing communal breeding, and adept at following a lead pigeon when flying en masse, with flocks almost magically swerving in unison to avoid predators. (In fact these birds should be remembered for their anti-violence stance, since they almost never physically fought with other creatures.)

The exact causes of the passenger pigeon’s extinction are unclear, but massive hunting and persecution were among the most devastating impacts, since the bird was very poorly adapted to escape people. It relied on large numbers, rather than hiding or fleeing, to avoid predation. Its other fatal peril was habitat destruction for agriculture and other development, as humans razed the millions of acres of hardwood forests the birds needed for food and shelter.”

Aubadon website, in their article Why The Passenger Pigeon went Extinct, are even starker:

“The professionals and amateurs together outflocked their quarry with brute force. They shot the pigeons and trapped them with nets, torched their roosts, and asphyxiated them with burning sulfur. They attacked the birds with rakes, pitchforks, and potatoes. They poisoned them with whiskey-soaked corn. Learning of some of these methods, Native American tribe Potawatomi leader Pokagon despaired. “These outlaws to all moral sense would touch a lighted match to the bark of the tree at the base, when with a flash — more like an explosion — the blast would reach every limb of the tree,” he wrote of an 1880 massacre, describing how the scorched adults would flee and the squabs would “burst open upon hitting the ground.” Witnessing this, Pokagon wondered what type of divine punishment might be “awaiting our white neighbors who have so wantonly butchered and driven from our forests these wild pigeons, the most beautiful flowers of the animal creation of North America.”

Ultimately, the pigeons’ survival strategy — flying in huge predator-proof flocks — proved their undoing. “If you’re unfortunate enough to be a species that concentrates in time and space, you make yourself very, very vulnerable,” says Stanley Temple, a professor emeritus of conservation at the University of Wisconsin.

Even as the pigeons’ numbers crashed, “there was virtually no effort to save them,” says Joel Greenberg, a research associate with Chicago’s Peggy Notebaert Nature Museum and the Field Museum. “People just slaughtered them more intensely. They killed them until the very end.””

It would have been difficult to see the passenger pigeon, in its flocks of billions, as a vulnerable creature. But, like the dodo, the passenger pigeon’s weakness is a perfect metaphor for innocence lost. The hyper-social birds flocked together and relied on their numbers and collective efforts to survive. In the spring, when the passenger pigeons returned from their winter excursions, they were hunted in their thousands by humans who had gone hungry all winter. And, soon enough — before anyone even really got a handle on the problem — there were none left. The birds that had blotted out the sun were gone.

Charles Darwin, the great naturalist who discovered so much about the Origin of the Species and natural selection — he was famously inspired by a visit to the Galapagos islands. The islands, by providing isolated environments for species to develop and adapt, were rich in biodiversity. It was his discovery — on those islands — of the finches that led to so much of his understanding of natural selection. Every island had its own population of finches, with the size and shape of the beaks perfectly adapted to the food source available on the mountain. It was this realisation — that the finches may have had a common ancestor, and natural selection had led to such a diversity in the beak forms to adapt to where they lived — that helped Darwin and Wallace towards their theory of evolution.

Yet the Galapagos islands are famous also for their giant tortoises — in accordance with the general rule that on islands, creatures tend towards becoming gigantic or tiny. And, when Darwin’s voyage on the Beagle was taking place, they left a trail behind them: the empty shells of the delicious giant tortoises. As a good source of protein… well, I’ll quote from PD Smith’s review of a book on the subject: “The giant tortoises were “a captain’s dream come true”, and as a result many tortoises spent their last months wandering the decks of ships, waiting to be eaten. (One resourceful tortoise reportedly went missing on board a ship, only to be discovered two years later living in the hold among the casks.)”

This is not a new phenomenon. Where-ever humans have been, life has suffered, and extinctions have usually followed. Just ask the wooly mammoth. When humans reached Australasia, 45,000 years ago, 23/24 of the larger species went extinct within a few centuries. Yuval Noah Harari, in his book, Homo Sapiens, puts it best: “Were the Australian extinction an isolated event, we could grant humans the benefit of the doubt. But the historical record makes homo sapiens look like an ecological serial killer.”

I know that there is a fraction of the audience who has been listening to this hymn to biodiversity and — essentially, ultimately, thinking — “So what? If a few obscure finches or tortoises or woolly mammoths go extinct, sucks to be them, but we have evolved to be the dominant species. It may be sad that such creatures are lost forever, but we don’t mourn the billions of natural extinctions that happened in the past, so why should we mourn those that are happening now? It’s a small price to pay for the progress we’ve achieved.”

I’m not trying to shame anyone who thinks this way. The fact is, we all look at things from an incredibly anthropocentric point of view. If you don’t believe me, consider the cuteness factor — people in general are far more concerned about the prospect that something fluffy or cute like a panda, a penguin, or a polar bear might go extinct as compared to some obscure species of beetle, or species that die off due to overfishing. And most of us, myself included, are perfectly happy to eat animals even when it’s not necessary for our survival. And, of course, all of this has been an incredibly human-centric discussion, hasn’t it? We have talked about the end of the world as *we* know it; this has been the great threat. The collapse of human civilization — even the extinction of our species — may prove beneficial for many other species in the long run (although I doubt there would be as many chickens or cows as there are today.) I do think it’s a tragedy that so many forms of life are under threat, but that’s only because I view life as inherently valuable, and I’m still the one assigning value to things. I think most people can see the quiet tragedy in the moment when the last of its kind dies, and the unique body, mind, and presence of another creature is lost to us forever. But this isn’t a show about the end of the world as they know it; it’s a show about the end of the world as we know it. So why does biodiversity matter — from a selfish perspective?

For a start, we rely on the bountiful munificence of nature for so many of the things we enjoy. From the silk from spiders to the foods we eat, plants and animals provide us with so much — and yet they rely on complex ecosystems to survive and prosper, and, over time, many of these species have come to depend on each other in an intricately interlinked way. Consider that many plants, up to 1/3 of species, require animals to pollinate them — which is why the colony collapse disorder that is killing bees is such a terrifying prospect. Ten years ago, a man named Dave Hackenberg discovered that bees were disappearing. Not dying, just disappearing. Unlike previous plagues which left massive piles of dead bees like Atilla the Hun piled the skulls of his enemies, CCD left many hives completely empty, leading some bloggers to dub the phenomenon “the bee rapture.” The eeriness, and the fact that the way we depend on the bees and other pollinators to survive is far more obvious and direct than many other examples of biodiversity loss, led to a lot of press attention for this story compared to others. This was, at least in part, a human phenomenon — with a type of pesticide called neonicotinoids implicated in making the bees more vulnerable to a specific parasite that was killing them off. Recently, CCD has shown some signs of slowing down, and some studies show that with the rate of death decreasing, populations are recovering. Since bees can reproduce quickly, they’re less vulnerable to extinction than big, slowly-reproducing animals like pandas; and the ban on many neonicotinoids has helped the populations to recover. So this is one apocalypse that seems unlikely — at least for now — and good news in how we humans can change our behaviour to head off ecological catastrophes, even if they are of our own making. Biodiversity is essential to all systems on earth, and a third of plant diversity is expected to disappear by 2050. Today, there are 80,000 edible plants on earth, but only 150 are cultivated. Climate regulation and crop pollination are big examples of natural global systems that rely on biodiversity. Monocultures and cultivation of only high yield crops has led to a decrease in biodiversity and uniform ecosystems, as well as soil degradation and biodiversity loss. When you consider the strain that our demands — and our careless destructiveness — put on ecosystems, it’s a miracle that they are as resilient as they have been. We cannot take this for granted forever.

The abundance of flying insects has plunged by three-quarters over the past 25 years, according to a new study that has shocked scientists.

Insects are an integral part of life on Earth as both pollinators and prey for other wildlife and it was known that some species such as butterflies were declining. But the newly revealed scale of the losses to all insects has prompted warnings that the world is “on course for ecological Armageddon”, with profound impacts on human society.

The new data was gathered in nature reserves across Germany but has implications for all landscapes dominated by agriculture, the researchers said.

I recently saw a pitch from a group of scientists in the zoology department at my University. They were talking about how they were fascinated by a rare Hawaiian mollusc that had extraordinary regenerative powers. The creature was capable of recovering from all kinds of injuries. There are tiny marine animals — known as “snail fur” or Hydractinia.

They look a little bit like a troll-doll, with their furry heads used for catching tasty morsels that float by in the ocean. But they are special: when fish bite these heads off, the heads themselves can regenerate. Scientists have observed stem cells from the creature literally flow to the wound, where its head was bitten clean off, and repair the damage. There is an African mouse that can repair and regenerate itself at an incredible rate. Any one of these creatures could provide incredible genetic information for scientists and even medics: with billions of years to optimise, nature may be capable of producing far greater solutions to the problems that humans find. Just look at photosynthesis. By killing species, we are destroying information that could prove immensely valuable to humans in the future, especially now that Crispr-Cas9 has made genome editing much easier (as we talked about in our episode on the Singularity.) What if we need to find a new kind of biofuel, or a new kind of food to feed a growing population? Many projections for feeding the growing population — as distasteful as you might find it — rely on us getting a hell of a lot of our protein from insects. But if you’ve just killed the last equivalent of a cash cow in the insect world, you’re out of luck.

We know that ecosystems rely on biodiversity to thrive. And, as clever as we might think we are, we still owe so much to the natural ecosystems that are around us. There is a theory of the Earth as Gaia — an integrated ecosystem, self-regulating. In some ways, it makes a lot of sense — look at the plants, which produce oxygen from carbon dioxide; and the animals, which produce carbon dioxide from oxygen. Symbiosis is the phenomenon where two creatures depend on each other.

Consider the goby fish and the shrimp. The shrimp digs a burrow into the sand and both organisms live there. Because the shrimp is almost blind, the goby fish will touch the shrimp when a predator is near. This is just one of billions of symbiotic relationships — relationships that we understand well, and relationships that we have no idea about. Like it or not, we are still an animal; we still depend on this complex web of ecosystems — and, if we continue to short-sightedly smash parts of it, we may well be setting ourselves up for a world of trouble.

Beyond biodiversity, there are other looming ecological catastrophes that should keep us all up at night. Like, for example, the studies that show that — at the rate we’re going — we can only continue farming for another sixty years. Your children might live in a world where farming is impossible. The issue is topsoil degradation. The United Nations released a very alarming study describing the impact that modern, industrialised farming is having on the landscape. A third of the planet’s land is severely degraded and fertile soil is being lost at the rate of 24bn tonnes a year. Although sub-Saharan Africa is the worst affected — and soil degradation, and therefore competition over the remaining fertile land, has already exacerbated wars in the region — even in Europe, a billion tonnes of topsoil is lost annually due to these destructive agricultural practices. Since the fertile, uppermost layer of topsoil that’s good for growing takes over a thousand years to regenerate just 3cm, if we continue along this road, it’s going to become increasingly difficult to feed a growing population even as agricultural technology expands. Even as food demand is projected to increase by 50% over the next fifty years, the land that’s currently farmed may decline in productivity by up to 30% due to the degrading soil. To put it even more starkly, by 2050, if current trends continue, there may be only ¼ of the farmable land per person compared to 1960. Some of this productivity gap can be made up with technology, but when we continue to rely on technological revolutions to save us from our unsustainable lifestyles — in so many different fields of endeavour — we are setting ourselves up for a fall somewhere. And this is all because of unsustainable agricultural practices.

Destroying soil is nothing new, and has in fact led to civilizational collapse in the past, as well. Given this, it’s surprising that it’s still a problem that’s not discussed as often as you’d think of — for a potentially existential threat. This via National Geographic:

“Modern examples of the impact of soil erosion are well-known: the Dust Bowl in the American and Canadian prairies, the erosion of China’s Loess Plateau, the famine in Africa’s Sahel. Ancient societies also reaped what they sowed when it came to their farming practices.

“The Romans still plowed themselves out of business, as did the Greeks, and Easter Islanders,” says David Montgomery, who studies topography at the University of Washington in Seattle and is the author of Dirt: The Erosion of Civilizations.”

A Time Magazine article on the topic has explained how human practices are leading to degraded agricultural soils:

“Soil is being lost at between 10 and 40 times the rate at which it can be naturally replenished. Soil is a living material: if you hold a handful of soil, there will be more microorganisms in there than the number of people who have ever lived on the planet. These microbes recycle organic material, which underpins the cycle of life on earth, and also engineer the soil on a tiny level to make it more resilient and better at holding onto water. Microbes need carbon for food, but carbon is being lost from the soil in a number of ways. Simply put, we take too much from the soil and don’t put enough back. Whereas the classic approach would have been to leave stubble in the field after harvest, this is now often being burnt off, which can make it easier to grow the next crop, or it’s being removed and used for animal feed. Second, carbon is lost by too much disturbance of the soil by over-ploughing and by the misuse of certain fertilizers. And the third problem is overgrazing. If there are too many animals, they eat all the plant growth, and one of the most important ways of getting carbon into the soil is through photosynthesis.”

In our episode on Malthus, we talked about how Norman Borlaug, the Green Revolution, and our ability to — for example — widespread-deploy chemical fertilisers to feed the population that was growing exponentially. This headed off Malthus’ fears of famine. But, as we mentioned there, the Green revolution might also have unintended consequences such as reducing the biodiversity of the crops that are used, rendering them more vulnerable to diseases or changing environmental conditions. The topsoil degradation may be another unintended consequence. By intensively farming land and artificially pumping fertilisers into the soil, we may be destroying other nutrients and microbial action at a faster rate than nature can replenish them.

Perhaps a technological solution can be found — if we understand soil better, and could perhaps modify the micro-organisms that regulate it at the moment to replenish it more quickly. The fertilisers and agricultural techniques of the future might not be so destructive. But relying on such breakthroughs to even be possible is a risky game.

And this links to another, interrelated crisis which also owes a lot to the unsustainable practices of humans. The more degraded soil gets, the less capable it is of holding water, and the more water you need to use in irrigation. When the soil can’t hold water, it flows directly through the water table to the sea, contributing to sea-level rise — it may be the case that up to half of the sea-level rise that’s been observed in some agricultural regions is actually due to runoff from irrigation. So, as soil degrades, there is going to be an even bigger pressure on freshwater stocks.

One in six people in the world today is “water-stressed”, meaning they don’t have sufficient access to drinking water. Water stress is only getting worse — the demands for freshwater continue to increase, but on the whole, we’ve done nothing large-scale enough to really affect the supply (which, after all, mostly comes from the sun evaporating water from the oceans and land.)

Of the world’s major aquifers (gravel and sand-filled underground reservoirs), 21 out of 37 are receding, from India and China to the United States and France. The Ganges Basin in India is depleting, due to population and irrigation demands, by an estimated 6.31 centimetres every year. Jay Famiglietti, senior water scientist at Nasa, has warned that “the water table is dropping all over the world. There’s not an infinite supply of water.”
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Changing climate and precipitation patterns are at least partially responsible — and, like the case for topsoil, human demands are now getting to the point where we cannot expect natural processes to compensate in time. And it is well-documented that water stress leads to wars.

Let’s talk about war, for a minute. There are several reasons there are fewer wars in the modern era, by and large. I don’t want to diminish the suffering of anyone involved in conflicts today — war remains brutal, terrible, a scourge on humanity — but there are far fewer wars than there used to be. And a major reason for this is the pax atomica — nuclear weapons have meant that big powers can’t go to war with each other. But the main reason for wars, throughout time immemorial, is: “those people over there have some shiny thing and I want to take it.”

This is not how wars work in the modern world. There is no longer any economic sense in ‘plunder’. Part of this is that so much of wealth is intangible. If you invaded London and occupied the square mile, the City, the financial services district that is the heart of so much of the country’s wealth — you wouldn’t own that wealth. Instead, the financial markets would probably crash, and you’d lose it all — as well as not being able to sell or use those resources yourself to generate wealth. And, even in places that are wealthy due to their huge natural resources, the cost of war is probably prohibitive. As I write this, oil is worth $50 a barrel, and Iraq is producing 5 million barrels of oil a day. That means the oil (not including the cost to extract or refine it) is worth $91bn a year. But the Iraq war has cost more than $2trn and may end up costing $6trn when you consider the benefits that must be paid to soldiers. The point being that, if you interpret it as a straightforward war to seize oil production and keep it, it’s still not worth it. There is no longer much value in going to war to take another person’s stuff and enrich yourself that way.

At least, not with natural resources the way they are currently priced and valued. In the future, will there be wars fought over freshwater supply? Water wars might seem like a hypothetical part of a future, dystopian world where the population has vastly increased and we’ve screwed up the environment beyond recognition. But, of course, it’s not the Mad Max world of the future — it’s already here. To quote from the analysis from The National Interest magazine:

“Water stress acts as an accelerant, increasing the likelihood of conflict. Moreover, water scarcity-fueled instability can have dangerous security implications for wider geographic regions.

Take Syria as an example. Between 2006 and 2010, the country was hit hard by drought, which wiped out rural livelihoods for many and caused significant internal displacement across the country. Internal displacement in turn helped stir up a pot that boiled over into all-out civil war in Syria, eventually spreading to Iraq. Over the last two years, ISIS has viewed water access and control as a primary strategic objective of their campaign, and has commandeered hydroelectric dams, irrigation canals, reservoirs, pipelines, and other water infrastructure to cement territorial gains.”

And this is a further point for environmentalism from an anthropocentric point of view. Even if all that you care about is humans, human lives, and human suffering, sleepwalking to ecological disaster is terrible for all of us. If this happens, there will be more wars, and more conflicts over the scarce resources. We will have to devote ever-increasing efforts to mere survival. We won’t have access to things we take for granted and depend on to live — as millions in the world today do not have access to these things. Technology may come to the rescue, of course — and, for example, a widespread campaign of conservation and desalination could provide more water for people (although it would come at an energetic cost.) But I don’t believe technology will find it easy to improve on nature, and certainly not at the same scale, certainly not at the same cost.

People talk about e.g. “cloning” meat and growing it in factory labs — I don’t see this as being cheaper than traditional farming for a very long time. If it ever does become cheaper, it will be because we have triggered this ecological catastrophe that has made living off the land so much more difficult.

This is really just a small snapshot of the various environmental catastrophes that could occur; I’ve only begun to scratch the surface on this issue. But I want to end with the story of an environmentalist and a crazy theory that might have some sense to it.

James Lovelock is a fascinating scientist. He worked at NASA for many years, and he was one of the first people to detect high concentrations of choloroflourocarbons or CFCs in the atmosphere — that were later discovered to be the main culprits behind the hole in the ozone layer. Incidentally, the CFCs and the ozone problem are really some of the most promising examples of humanity’s responses to pollution and our impact on the environment — the most harmful chemicals were banned, regulated, and now the hole in the ozone layer is gradually recovering.

Lovelock has also been an outspoken scientist on political and environmental issues for many years. Personally, I think that he’s made some pretty wild and irresponsible comments that he’s later had to back down from — like, for example, in 2006 when he said that “as a result of global warming, “billions of us will die and the few breeding pairs of people that survive will be in the Arctic where the climate remains tolerable” by the end of the 21st century, or that 80% of people would die by 2100.” Both of these, in my view, are pretty ridiculous predictions — and it’s kinda ironic that just five years later he was describing himself as an alarmist and admitting that he’d made a mistake. Climate change will be bad — we’ll come onto that in the next episode — but I don’t think it will be *that* terrible; he’s basing all of that on the very worst-case scenarios which have since been considered more unlikely to happen by scientists. Point is, Lovelock may be a genius and a fellow of the royal society, but his environmental proclamations can be taken with a grain of salt.

All that said, towards the end of his life, he’s changed tack. He essentially now considers climate change and environmental degradation more generally to be an unfixable problem. Quoting from a review in the Torygraph of his latest book, A Rough Ride to the Future:

“Ultimately, he suggests, climate change is down to ignorance, not negligence — but while we do not yet know its exact contours, the process is both extremely serious and probably unfixable. Unlike the situation with CFCs, or chlorofluorocarbons, a generation ago, there are too many actors — countries, companies and individual humans — that would need to be cudgelled into self-denial if the status quo were to be retained.

Where he differs from the consensus, however, is in suggesting that this might not be such a bad thing. What we are seeing around us, Lovelock argues, may be the large-scale destruction of the planet’s ecosystem by rapacious humanity. But it may also be “no more than the constructive chaos that always attends the installation of a new infrastructure”.

Humanity is already concentrating itself in bigger and bigger cities, so rather than trying to “save the Earth”, or restore some artificial version of a normal climate, why not live comfortable lives in clustered, air-conditioned mega-cities? This serves ants and termites perfectly well, he argues — as well as the inhabitants of Singapore.”

Lovelock is also famous as the originator of the Gaia hypothesis. The mythical Gaia was the Greek goddess of the Earth, or Mother Earth — and the ancients personified the Earth as a single, living organism. The idea of Lovelock’s Gaia hypothesis is that the Earth is, in many ways, a single living organism; with organisms interacting with their surroundings to form a complex, self-regulating system that maintains the conditions that make life favourable. In some ways, it makes sense that natural selection would select for creatures that can subtly change their surroundings, allowing a greater range of conditions to be suitable for life. Global temperature, oxygen levels, liquid water, and the salinity of the oceans may all be — in some sense — maintained and regulated by organisms within tolerable levels for those organisms to survive. That’s the idea, anyway. You might think the idea of Mother Nature as an actual force in the world is slightly too Peter Paul and Mary, and you may be right…

Now, I stand with the many other scientists in arguing that there’s really not enough evidence to believe in the Gaia hypothesis as it’s formulated. I think it goes way too far; I don’t think biological feedback mechanisms are really that strong — or I’d be able to list a huge list of these feedbacks that show how the dominant factor in, e.g., the Earth’s temperature, is one form of life or another. But, at the same time, we evolved to live on this Earth alongside other creatures. There are intricate and complex links between the species that exist on this planet. But consider this: the creator of the Gaia hypothesis, who came up with it in the 1970s… in 2017, he is essentially saying that our destiny is to kill Gaia. To replace Gaia with an artificial life-support system, rather than the natural one that has sustained us throughout our history.

Perhaps this can happen. Perhaps, even, it inevitably will happen. There are two different worlds when you’re talking about environmental issues: the world of things that humans can and should do, and the world of things that humans actually do, which is driven by self-interest. There’s enough food in the world to feed us all, but, guess what? Millions of people will still starve to death this year. I am not innocent in this. I benefit from a rich and decadent lifestyle, a lifestyle of waste, consumption, and destruction — just like many of the people listening here. So it’s not ridiculous to think that — if we can’t even equitably feed ourselves — we will not be able to save the environment, and will have to replace it with an artificial life-support system — that the whole world will become some bizarre, high-tech super-city, with food grown in labs or by artificial photosynthesis, and water purified from the oceans so that it is safe to drink. It’s possible that this can happen. But if Lovelock is, at long last, correct — and we are witnessing the transition from being a species that depends on the natural environment to survive, to one that entirely replaces it — then I really don’t think it’s obvious that this transition will go smoothly. I think there will be blood. And, if we’re not incredibly careful, it won’t just be the end of the world as we know it for millions of other species. Homo sapiens could be amongst those who fall from grace. Unthinkable, right? There used to be billions of passenger pigeons, too.

Thanks for listening etc.


Next episode, to continue with this wonderfully cheerful theme, climate change.


Climate Change

So: here we are. The topic of today is going to be climate change. I am going to try to be as unbiased and thorough as I possibly can. This is an area I work on, and it’s an area that I’ve read an awful lot about. That can make explaining something more difficult, as you try to remember all of the salient points that need to be mentioned and explained. But I will try.

The first thing to understand is the difference between weather and climate. Weather is the local conditions — for example, temperature, precipitation, humidity, and so on — that are in your area, for a small period of time: perhaps a few weeks at the most. Climate is more like the average of these conditions over a period of years or even decades. So, for example, the fact that it’s particularly warm today — or this week, or even this summer — is not necessarily categorical evidence that the climate has changed compared to last year. Equally, the fact that you can bring a snowball into the Senate floor (in the US) and drop it on the ground: that doesn’t mean that things are getting colder.

Climate change may have an influence on weather conditions. For example, recently, in the terrible 2017 hurricane season that has affected so many, there has been a lot of talk about this; partly because having that many category five hurricanes in a single year is very unusual, and partly because the destruction they’ve caused has been widespread and terrible. We don’t know what causes hurricanes to form — there is no closed model for this, although people have lots of ideas. It’s okay in science to accept what we don’t know, and, in climate physics, there’s a lot we don’t know. But being uncertain about potential catastrophe is not an excuse to do nothing about it. As many have pointed out, if you’re driving along a cliffside in foggy weather and you don’t *know* if there’s a turn ahead, it’s still rational to apply the brakes.

The second thing I’d like to do is explain why we think the world is warming, and what it’s got to do with carbon dioxide emissions. To do this, it might be helpful to go back over radiation from our older episode Unusually Hot, but I’ll briefly explain here.

Lots of factors determine how warm the surface temperature of the Earth is. The most important one, obviously, is the fact that we have a Sun; without this, the temperature would probably be much closer to -250 celsius and there’d be no point having this conversation.

Any object with a constant temperature is in thermal equilibrium. It’s really pretty simple: as much heat flows into the object as heat that flows out again. If more heat flows in than out, the object heats up. If more heat flows out, it cools down. The Earth absorbs some radiation from the Sun; it also reflects some radiation without absorbing it; and it also emits radiation of its own. Obviously, because outer space is empty, only radiation really matters in heat transfer between Earth and Sun.

Luckily, physics has an amazing formula for how much energy an object should emit by radiation. It’s called the Stefan Boltzmann law, and it says that the power emitted is proportional to the temperature to the power of four. So this is great — we can calculate how much energy the Sun is emitting, we can calculate how much reaches us here on Earth, we can estimate how reflective the Earth is and so we can figure out how much the Earth absorbs. Once we know how much radiation the Earth absorbs, we know what heat is flowing into the Earth. So then we just say — aha! If the Earth is in thermal equilibrium, then it must re-emit all of that energy. From this, we can use our fancy Stefan Boltzmann law, only in reverse. We know what power the Earth is emitting — we have to know, because it’s the power that keeps the Earth in equilibrium. So we can figure out its temperature. And if you do this, you get something like -20 degrees Celsius. So we should all be dead. What’s going on?

Obviously, a little bit more detailed physics is needed. When an object emits radiation, the temperature it has doesn’t just tell you how much — it also tells you the frequency of the radiation. And we know this, really. When you heat up a poker, it’ll start by glowing yellow, then red, then eventually white hot. That’s because, as the temperature increases, the frequency of the radiation it emits is also changing. And, as we mentioned in Unusually Hot — you’re emitting radiation, right now! But you can’t see it, because it’s in the infra-red: our eyes are tuned to visible light. That’s why we call it visible.

The Sun’s surface is at around 6000 kelvin, where 273K is zero degrees Celsius and the units are the same. Our surface temperature is closer to 300 kelvin, give or take. So clearly the Sun emits different frequency radiation than the Earth, because… it’s way hotter. And Earth is basically emitting infrared radiation, just like we do: which is why it doesn’t glow.

Then you add in an atmosphere. And now things start to get really interesting. Because, as we’ve mentioned, matter — or, to give it its technical name, stuff — can absorb and interact with radiation. But the type of radiation it can interact and absorb with depends on the matter. It depends on the energy levels of the atoms in that matter.

So now imagine a particular type of molecule in the atmosphere. It has a particular set of energy levels — photons that it likes to absorb and re-emit, at particular wavelengths. There are two kinds of radiation that might interact with this particle. There’s the shortwave radiation from outer-space; the powerful radiation directly from the Sun. And there’s the longwave radiation that is emitted from the Earth. Such a molecule might have energy levels too small to interact with the shortwave radiation; so this stuff can pass more or less straight through. But the longwave radiation from Earth — that can interact with this molecule.

What does this mean? The radiation from Earth that would usually escape to space is absorbed by the particle. It’s then re-emitted, but, crucially, at a random direction. This means that around half of it will head back towards Earth, heating up the atmosphere and the Earth. Some of the radiation that could escape to space is instead blocked. The greenhouse gases — because this is what we are talking about — act like a blanket, that trap heat.

I’m afraid that this is simply non-negotiable. You can argue about what impact doubling CO2 concentrations in the atmosphere, as we are currently doing, might have. You can argue about the economics of climate change, if you want to. But you cannot argue, as I have seen — particularly by one individual I won’t name who, surprise surprise, works for the oil industry, that the greenhouse effect is not real. We know that this is happening. Without it, the Earth would be too cold to sustain life. It is a real phenomenon which has been understood for well over a century. And even in his famous paper where he first described it, in the early 1900s, the scientist Arrhenius pointed out that human influence may conceivably affect the climate: “the slight percentage of carbonic acid in the atmosphere may, by the advances of industry, be changed to a noticeable degree in the course of a few centuries.”

Unfortunately, Arrhenius imagined that this would be an effect that we “might just notice” in “a few centuries.” Instead, carbon dioxide levels have increased from 280ppm when satellite measurements first started to well over 400ppm; they look set to double this century compared to preindustrial levels.

So I’ve described how the greenhouse effect works, and how we actually need some greenhouse effect to ensure that our planet isn’t too cold for life. But, of course, disrupting this balance by emitting more CO2 will cause our planet to warm by some degree. This is obvious.

We can actually quantify the effect of greenhouse gases by looking at the “top of atmosphere flux” — a very famous graph which I will include in the shownotes. NASA and so on stick satellites up in space that measure the radiation that’s emitted from the Earth’s surface — the stuff that makes it past the layer of clouds and greenhouse gases. Then they compare it to what the Earth would emit if it wasn’t obstructed by anything. And they find a significant amount of the radiation is absorbed and scattered by the atmosphere, some of which goes back down to Earth. Since they can measure the wavelengths of the escaping radiation, they can even show you on the graph precisely which wavelengths are being absorbed. And — guess what — they correspond to exactly the wavelengths that we know are absorbed by carbon dioxide, methane, nitrous oxide, and water vapour in lab experiments that we do when we test which wavelengths are absorbed by various gases.

Using this, we can estimate how much energy is “trapped” by carbon dioxide vs water vapour vs methane etc. So you might have heard that methane is considered a “worse” greenhouse gas than CO2, because it traps more heat — and you can see on the graph that methane’s absorption is at higher wavenumber, hence higher energies, so this is broadly correct. (The other side of the methane debate is that methane doesn’t last that long in the atmosphere — a few years — while CO2 remains where it is for centuries.)

So we can tell you how much energy is being taken out of the system by CO2, and how much difference more CO2 is going to make. This is fairly easy radiative physics. You might be wondering — if this is all there is to it, how come climate physicists are so uncertain and their models can’t perfectly predict the temperature?

So this brings us onto the third thing I’d like to say is that the world, and the climate, cannot be simply expressed. For this reason we like to call it a climate system, or even an Earth system to indicate the whole Earth. There are thousands upon thousands of feedback loops and so on that make things more difficult. Let me give you an example. A huge resource for people who are interested in studying the climate is “paleoclimate data”. Using archaeology and geology, we can work out what the temperatures and sea levels of the world were many thousands of years ago. For example, ice-cores in the Arctic and Antarctic provide valuable data on atmospheric CO2, because when the ice froze — however many thousands of years ago — it captured some of that CO2. We can model how this works today, and infer what the CO2 content must have been in the past. Rocks form differently underwater; from this and similar observations we can calculate sea levels. So we know, in broad terms, what Earth’s climate was like in the past, and we’ve been constructing a more and more detailed picture of it for many years.

Long ago, perhaps earlier than 650 million years ago, many people think that the entire world’s surface was covered with ice. This sometimes gets called “Snowball Earth”, for reasons I’m sure you can imagine. But it’s difficult for us to see how this can be the case. The Sun isn’t changing all that much in how much light it emits; the Earth’s position in its orbit does fluctuate, but it would clearly have to be a pretty big change to cover everything in ice! Under some models of Snowball Earth, the Equator — currently the hottest places on Earth — were as cold as Antarctica is today. That seems hard to imagine based on any event.

Instead, the actual mechanism involves a positive feedback loop. There is a small change to the climate system initially, but this acts in such a way that it reinforces itself. Before long, you have something that runs away with itself, accelerating towards a new equilibrium.

So how does this happen? Let’s say the climate system gets a particularly big kick. Maybe continental drift acts in such a way as to cool everything down — maybe there are orbital changes — maybe there’s a supervolcano that dumps dust and ash into the atmosphere that cools things down. You’ll remember from TEOTWAWKI 7, Supervolcanoes, that this can happen — and has led to mini Ice Ages in the past. The natural response is that the North and South poles, which are colder anyway due to the Earth’s orbit, start to freeze over. When they freeze over, you get… ice!

Ice reflects sunlight far better than water does — as you can tell, because it’s basically white, and if you’ve ever been fortunate enough to be somewhere really icy the glare can be a big problem. This means that it reflects a lot of solar radiation back to space. So, the idea is — gradually, over many thousands of years, the ice formed. It reflected more radiation back to space. This cooled the planet down, allowing more ice to form, reflecting more radiation into space, resulting in more cooling. Eventually, most of the planet was covered in ice. We know this effect is important in determining the extent of the polar ice caps — historically, it’s reinforced cooling trends. And Snowball Earth is actually a pretty stable climate again. The Earth is covered in ice, which reflects back lots of solar radiation; things stay at sub-Antarctic temperatures everywhere; and little kicks to the climate system don’t do much to warm things up.

But it’s also possible to emerge from a Snowball Earth type scenario — and, everyone who believes it happens must accept this, given the lack of snow around 😉

Many people suggest that the greenhouse effect was actually responsible for rescuing the Earth from its icy snowball state of always-winter and never-Christmas. Billions of cyanobacteria, a primitive form of life, were trapped beneath the ice. They fed on the organic carbon that lived under the ice for many many years, and emitted CO2. Normally, the cyanobacteria would be part of another cycle — absorption of CO2 by rocks as they weathered — but with the Earth covered in ice and snow, there was no way for the oceans or the rocks to absorb carbon again. Consequently, there was a big buildup of CO2 from these cyanobacteria (and volcanoes, too) that wasn’t subsequently absorbed: the atmospheric concentration of CO2 shot up; the Earth heated up and a band of the ice melted, and we got the same feedback effect in reverse. With the Earth heating up, the glaciers retreating, the climate was more temperate for these little cyanobacteria to regenerate the atmosphere again — and this may have led, eventually, to the Cambrian explosion of life.

So we can see in this that the Earth’s climate history and processes are complicated, but CO2 has always been an important factor — one of many, but an important factor — in determining the Earth’s overall temperature. Also important — and crucial to the fact that our understanding of climate is, at present, so uncertain — are the presence of these feedback loops. I’ve described the ice-albedo one, which is thought to be very important: and you can see how this will be very important. I guess it’s easy for people who aren’t sold on this issue to think — so what if the polar ice cap melts, it’ll kill a few polar bears or penguins but that’s a small price to pay for progress. The issue, if you really want to look at things from a super human-centric point of view, is that the ice-cap melting could kick the climate into an unstable regime where quick, dramatic warming takes place.

There are other feedbacks, too. Warmer oceans means more water evaporates; more water vapour in the atmosphere: this is also a greenhouse gas. Of a great deal of interest, and with no small amount of complication, is the CLOUD feedback. Clouds are also very important in the Earth’s radiation balance. Broadly speaking, low clouds reflect more sunlight, while high clouds trap more heat. (I am simplifying the literally hundreds of research papers on this topic, but you understand.) So how much will climate change affect this particular feedback? Will we get more low clouds, that reflect sunlight and cool the Earth, or high clouds that trap heat and warm it up? It’s not completely clear how large this effect is, but most scientists are pretty convinced that the net effect is to further warm the climate system. Clouds are probably the biggest uncertainty in modelling the climate that we have at the moment. And uncertainties do remain, which people are still furiously working on trying to understand and quantify.

Unfortunately, the pernicious nature of denialism is helped out by how complicated Earth’s climate system is. Things are particularly complicated, but one of them is that the climate naturally oscillates — by a smaller amount than total human warming — roughly every decade. It cools, then it warms again. These are in part caused by oscillations you’ve probably heard of if you’ve followed the debate — El Nino and La Nina.

You can see why this is such a big problem. It means that, every couple of decades, we see a ‘pause’ in the observed warming of Earth’s surface temperatures. We came out of one just now that lasted quite a while, with 2015 and 2016 being the hottest years on record again.

But this is a really bad problem for communicating the science. Because when we emerge from a ‘pause’ in warming like this, it coincides with natural cycles that warm up the Earth. Think about it like this — you have a straight-line graph going up, and you add to that a ‘wave’ graph that goes up and down. What you get is a flat line — when natural cooling cancels human warming — followed by a spike, when the two add up again.

But this spike occurs when natural processes are already warming the Earth. Most commonly cited as the culprit is El Nino. So it means that every time we see a spike in observed temperatures, climate skeptics can cite El Nino as being responsible. And it is, in part — but so are we.

The thing is — individual statistics for a year are not necessarily all that meaningful. For climate physics, which evolves over decades, you may have to average across 10 years, or 20 years, to see an observable result. So I’m not willing to bet any of my meagre fortune with you guys that it will be warmer in 2018 than 2017. That’s not how the climate works, as best as we can tell. But I am willing to bet that it’s warmer in 2030 than it was in 2010. And that it’s warmer in 2050 than in 2030. Strangely enough, not many people seem willing to take you up on an offer like that.

I think one of the things that scares me most about climate change as a threat is not actually how terrible it will be. If you ask me whether I’d rather wake up in a world 100 years from now where nothing is done to address climate change — or a post-apocalyptic wasteland after a nuclear war — then I’ll pick the climate-change world every time. But what it does present is a unique set of challenges that we as humans are singularly, and catastrophically, bad at dealing with.

The problem is incredibly scientifically complex. Communicating scientific complexity to people is very difficult. The problem takes place over many decades — even centuries. This is a huge problem, because who needs to act on this? Democratically elected governments, corporations, and individuals. Democratically elected governments have no incentive to care about what happens beyond the next 8 years, or the next 10 years. Corporations might expect to exist a little bit longer, but ultimately, the profit motive will always come first for them. And many individuals don’t particularly care about what happens after they die; or, if they do — e.g. for the sake of their children — they may not always be willing to undergo the personal sacrifices that would help us in this quest.

— — — — — — — — — -

Hello and welcome to Physical Attraction, where you’re listening to the second part of our climate change episode. In the last show, I talked about how we know that climate change is happening, what causes it, and some of the feedback mechanisms in the physical climate system that make it difficult to predict. In this show, I’ll talk more about what the consequences of climate change will be, why I think it’s such a difficult problem to deal with, and what we can hope to do to help.

Last episode, we talked about how complicated the climate change issue is. And, alongside the complexity and uncertainty making predictions difficult, specific facts about the complexity of the problem make it so easy to spread misinformation. For example: yes, the Sun’s natural cycles do influence the climate. So do things like cloud cover; possibly even cosmic rays have some impact on the climate by encouraging cloud formation. Volcanoes have a big impact on the climate. And yes, the climate has always changed. These things are indisputable facts; few climate scientists would dispute this kind of thing. But few climate scientists would dispute the most important things you need to know about climate change: it is happening, it is us, it will get increasingly serious the longer we continue to do nothing, cutting emissions and mitigating climate change this way is the best thing we can do.

Let me give you a few examples as to how you might easily construct a denialist argument. And if you think I’m being stupid here, bear in mind that I’m taking these from articles or online arguments that I’ve actually read.

So, hey guys — it turns out that the oceans naturally release ten times more carbon into the atmosphere than we do! So why the hell are we worrying? Our impact on the planet is tiny, and it’s foolish to think that we could have a real influence.

That fact is technically somewhat true — the oceans do release roughly ten times the carbon that we do into the atmosphere. They also absorb all that carbon and more from the atmosphere, as part of the natural carbon cycle. In fact, by some estimates, of all the CO2 humans have emitted, over half has been taken up by the oceans. There are plenty of links in the carbon cycle — for example, plants and trees on Earth absorb huge amounts of carbon, and they release it again when they die. Some of the carbon is locked up in the bodies of those plants, animals, and trees that die — and it sinks to the bottom of the ocean, or is buried underground. This becomes fossil fuels.

What we do when we burn coal, oil, and natural gas is disrupt the balance. We’re effectively removing that natural sink — the small fraction of plants and animals that end up buried underground, that helps to keep carbon levels stable. But we’re burning carbon that comes from plants and animals that died millions of years ago. Worse, when we deforest the landscape, we may be killing plants faster than new ones can grow. Even just a week or two before writing this, I read an alarming report that indicates that — due to deforestation in the tropical rainforests — they are no longer acting as a net sink of carbon. In other words, the death of trees due mostly to human activity is emitting more carbon than the new ones that grow can take up. This imbalance, which was only recently discovered, could be equivalent to all the car and truck use in the US combined.

Don’t let anyone fool you about specific aspects of the carbon cycle. The simple fact is that atmospheric CO2 has increased dramatically since we started burning fossil fuels. In preindustrial times, it was approximately 280ppm. Nowadays, it’s blasted well past 400ppm and consistently reads at those levels. James Hansen of NASA said that a safe level was 350ppm — and while that’s probably pessimistic, it’s true that this current amount is alarming. We have good data on carbon content from ice cores and other sources of record that indicate that the carbon dioxide content in the atmosphere hasn’t been this high for millions of years.

You don’t even have to believe in things like ice-core data, because satellites started measuring CO2 in the atmosphere back in 1955. Go find a graph of the Mauna Loa observations online — you will see that it’s been increasing every year since they started measuring it. What’s more, the average rate of increase since Mauna began measuring was 1.55ppm/year — but recently it’s been closer to 2.75ppm/year. Why, it’s almost as if — the carbon in the atmosphere is increasing as our emissions and our human activities that impact the land continue to increase… So if you have an alternative theory that explains why the CO2 in the atmosphere has been increasing due to natural changes in the carbon cycle, nothing to do with the sudden presence of humans pumping CO2 into the atmosphere, in a way that’s been unprecedented as far as we can tell for millions of years — please — publish it. You will win a Nobel Prize. Of that there is no doubt.

Here’s another way of constructing climate change denial that I’ve actually seen.

Yes, the greenhouse effect is real. But water vapour is a much bigger greenhouse gas than carbon dioxide — natural water vapour has a much bigger warming effect than CO2. I’ll bet scientists haven’t considered the effects of water vapour on the climate system.

The answer to this one… yes, of course we know that water vapour is impacting the climate system. If the Earth had no atmosphere at all — no greenhouse gases, no nothing — then you can do a simple calculation for what its temperature should be. You essentially say, okay, the Earth has to be in thermal equilibrium — that means that it absorbs as much energy as it emits. If you’re putting in more energy, then it will heat up; if you’re taking away more energy, it cools down. We can work out, based on how much radiation the Earth absorbs and reflects and so on, that the temperature would be 255K or -18 degrees Celsius. So thank god for the Greenhouse effect — without it, we’d all certainly be dead. It’s actually far worse than this, because, at -18C, the oceans would freeze and they’d reflect even more sunlight back to space, making the Earth even colder.

So why was the average temperature on Earth 14 degrees Celsius (pre humans)? The answer is that water vapour, methane, carbon dioxide, and other greenhouse gases warm up the planet.

This is why the particularly bonkers brand of denialists who tell you that the greenhouse effect isn’t real just don’t have a leg to stand on. Without the greenhouse effect, we would all freeze to death. It clearly has a very important impact on climate. But if we continue to enhance it with unmitigated carbon emissions, it could be cease to be our friend.

So I think by now — if I haven’t convinced you that climate change is happening, I never will. You’ll have to listen to someone more persuasive — or wait twenty years and see what the global temperature is. The temperature record shows warming. The CO2 record shows that CO2 is increasing. And I’ve explained how the two are linked.

But what will it do to us? And how can we hope to prevent it? This is what I want to come onto.

First: the consequences. The initial consequences we are already seeing. As the atmosphere warms up, it can hold a greater moisture content. This means that extreme weather events, such as hurricanes, will become more intense, with greater rainfall. Warmer sea surface temperatures where the hurricanes form will cause a greater level of energy to be imparted to the hurricane. Hurricanes may not become more frequent — we don’t know enough about the mechanism of how they initially form to say for sure — but they will become more intense. The same is true for droughts and forest fires. The annual cost due to extreme weather events in the US has doubled; between the years 1980 to 2015, it was $5bn, but in the years 2011–2015 alone, it was $10bn. Some of this will be due to chance, but not all. Flooding events will become more extreme as sea-levels rise due to the icecaps melting. Heat-related deaths will increase on the hotter days as ‘hottest-day-on-record’ records are continuously broken. Ecosystem destruction is worsened by climate change — vertebrate species (with backbones) are disappearing at a rate 114x faster than they already do. The oceans will become more acidic due to increased carbon dioxide, which turns water into carbonic acid. This kills wildlife. The Great Barrier Reef is probably already doomed.

Sea level rise due to the melting ice-caps threatens nations. By 2100, if we do not act, many island nations will be underwater. Bangladesh is already experiencing the fate that may lie in wait for many low-lying nations. There, every year, 20% of the country is flooded. Every 4–5 years, 60% of the country is flooded. The flooding events continue to get worse and more extreme. By 2100, these flooding events will be permanent: 20% of the country will be underwater for good. 30 million people will be displaced. It will be a slowly-unfolding refugee crisis unlike any the world has ever known. This is equivalent to all the refugees that there currently are in the world, from just one nation. Sea levels will rise between 1 and 4 feet by the end of the century. But sea-level rise is a lagging indicator, and unfolds over centuries rather than decades — usually. Melting ice-caps and expanding, warmer oceans will eventually — if nothing is done — by 2–3m by 2300. If all of Antarctica melts — which is really an outside possibility but could happen with very extreme climate change, if feedback loops go completely out of control — then it’s simpler to describe. The sea level rises by 80m and there is no more Florida. These changes will take place over centuries — no one is saying that these places will be underwater even within our lifetimes necessarily — but it should concern you. Microbes will thrive in a warmer climate. Diseases like malaria will spread more easily.

The sheer heat is a concern. Currently, we’re on course for more than two degrees of warming. The Paris agreement says that its aim is to limit the world to less than 2C from the pre-industrial era by the end of the century; we’re already somewhere between 0.7 and 0.9, and rising. If our emissions drop to zero by 2060, we’ll be set for 2.4C of warming. As we’re currently going, 3C looks more likely. In the worst-case where emissions continue to rise until 2100, this will be around 4.9C.

“Even if we meet the Paris goals of two degrees warming, cities like Karachi and Kolkata will become close to uninhabitable, annually encountering deadly heat waves like those that crippled them in 2015. At four degrees, the deadly European heat wave of 2003, which killed as many as 2,000 people a day, will be a normal summer. At six, according to an assessment focused only on effects within the U.S. from the National Oceanic and Atmospheric Administration, summer labor of any kind would become impossible in the lower Mississippi Valley, and everybody in the country east of the Rockies would be under more heat stress than anyone, anywhere, in the world today.”

Any amount of warming will produce some refugees. But when you get to 4 degrees, or six degrees — which are worst-case scenarios for the end of the century and practically certainties for 2200 if we do nothing — then you’re talking about having to evacuate entire regions of the Earth, which will become deserts.

Ultimately, I think the real menace from climate change is the factors that we don’t know about. We are kicking the Earth into regions that we’ve never seen — not as observers on this planet. We can infer what things may have been like through studying paleoclimate data. But we have no idea what might happen with the reckless and rapid warming that we’re currently causing. Damage to the biosphere — to life on Earth — could make things very uncomfortable indeed for humans by destroying the ecosystems we rely on, and pushing the Earth’s climate out of control.

Compared to the other existential risks on this list, climate change is a bit of an odd-one-out. It’s not as dramatic, at least to begin with: in fact, it’s so undramatic that it’s not self-evident to everyone that it’s happening. And the effects are delayed, and uncertain. We could get lucky, and continue along our merry way emitting carbon like there’s no tomorrow — or until we run out of fossil fuels to burn, or it becomes economical to stop — and still manage to avoid the worst-case scenarios of 4 degrees and 7 degrees that people are concerned about. But it differs from AI and nanotechnology, from meteorite strikes and supervolcano eruption in one crucial way: this is really happening. If we do nothing, it will get worse. And, amongst the many things we don’t yet know for sure, is just how bad it could get.

But we can face this crisis. In fact, the one thing that might make you happy from listening to the series that has, for months now, focused ruthlessly on the end of the world — is that there is always cause for optimism. Not a single one of the existential risks we’ve dealt with is in any way inevitable. The biggest threats to our continued existence aren’t strange starbursts from outer space, or even earthquakes and supervolcanoes from an angry Gaia. The biggest threats are the things we control. We have the power to stop this from happening. We can be remembered as the generations who had the foresight to change course, to make a difference, to start living in a sustainable way.

Because, you see, there are two stories that people might tell about the human race, a thousand years from now. If there are still humans, there will still be stories: this is who we are: this is what we do: we take the chaos and confusion and suffering and madness and beauty around us and weave it into tales that make sense so why should the human story itself be any different?

The first story goes like this. In the beginning, we were noble savages; and then we began to learn. We learned how to talk and how to tell each other stories. We were able to create things — abstract concepts — ideas like society, money, technology. Some of these came from our emotions, and we called these love and family, and some came from our intellect, and we called these reason and morality. But there were other, darker forces that went hand-in-hand; rage, greed, jealousy; paranoia, the stories from our feelings: and profit, selfishness, avarice, exploitation from the intellect. We learned the principles of science — we made great leaps in understanding nature — we learned how to reshape the world in our own image, and exploit the vast power that came underneath. We learned to achieve impossible things, things that no other species could ever dream of. We became godlike in our power and ambition compared to them.

But in the first story, this power is used carelessly and stupidly. The irony of such great intellect, such great knowledge — the arrogance of calling our species the wise ones — destroying so much of the planet that we called home. We destroy ourselves through greed and stupidity, and a lack of wisdom, in one way or another. We leave behind a planet far worse, and less hospitable.

In the second story, there is a turning point: as we realize the fragility of our Earth and the irreversibility of what we’re doing to it. Gradually, we learn and adapt — not just to the circumstances that surround us, but to understand what our actions mean for the future. Rapacious destruction, driven by profit, is replaced by sustainable harvesting, for the good of all — including those who will live on this planet after us. This is the story we want people to tell. It’s the story I want people to tell.

It is getting to the stage now where, for the first time, renewable energy is starting to become more economical than fossil fuels. Not just when you put a price on carbon, or when you factor in the true economic cost of continuing to burn these unsustainable fossil fuels and the environmental damage they cause — it’s just flat-out cheaper. As I have mentioned, free-market capitalism and western liberal democracy, although wonderful in many other ways, have not yet been particularly effective at reducing carbon emissions and facing up to climate change. In working against these forces, we’ve achieved limited success. For example, many countries in Europe have reduced CO2 — but principally by switching from coal, the dirtiest of all fuels, to natural gas, which produces fractionally fewer emissions but is still a finite, fossil fuel resource. But this was done fairly quickly because it was economical for companies to do so. Savings in energy-efficiency are also economical, for certain people. It is ridiculous that people continue to drive around in cars that get 17 mpg; the problem is that, providing people are willing to pay through the nose for petrol and get fleeced by auto companies — providing people are willing to make these choices — then gas-guzzlers are economical to buy.

But here, there is hope, too. The price of solar panels which we’ve talked about in previous episodes is declining rapidly. Electric cars may be cost-competitive with petrol-driven cars by 2020, and several governments — including that of China — have plans to phase out fossil fuel cars, and hence electrify the transport system, by 2040–50. The Paris Climate Accords united the world in a complicated, highly ambitious, but feasible goal of keeping warming to below 2C. It might depress you that Trump pulled out of the Paris Climate accords — essentially because it was one of the few achievements he could get that would please his base without congressional approval, by executive action. What depressed me more was how little understanding he showed of the issue, oscillating wildly in his speech from “climate change isn’t happening” to “Paris won’t make much of a difference”, citing an (incorrect) statistic that it would only save 1/10th of a degree of warming. (This actually amounts to a decade of warming at current rates, so even if this was all Paris did, it would buy us another ten years of time to research the problem and improve mitigation efforts.) But Trump is just one man. He will be out of office in three years, or in the very worst case scenario, seven years; the impact he will have on this battle, which will unfold over decades and centuries, will be small. And his actions galvanised the rest of the world to act on climate. China is now leading in the adoption of renewable energy — they have domestic motivations due to the smog and air pollution in their cities, but they are still leading — this would have been unthinkable a few years ago.

We can decarbonise our economy. And, in so doing, we achieve two incredible and worthwhile goals. First, we save ourselves from the risks of catastrophic climate change which could put an immense strain on civilization and render the lives of many millions miserable. We secure the future of our planet, of life on Earth.

The second goal we achieve by doing this is securing the future of our way of life. If we cannot do these things sustainably, then, sooner or later, resource depletion is going to kill us as a species. David Mackay, who wrote the book on sustainable energy, put it best when he wrote the dedication. The book is dedicated: “to those future generations who will have to live without the benefit of a billion years’ accumulated energy reserves.” As humans, we’re currently a little bit like the new student who gets his first student loan through and blows the entire lot on video games, alcohol, and fast food in a week. We need to grow up and accept the limitations. It is incredible that this world is capable of providing food to feed billions of us (if properly distributed) and resources to create so many incredible things. But it won’t be like this forever if we continue being wasteful and greedy.

The world’s governments currently spend billions of dollars on expensive militaries and counter-terrorism operations, and foreign wars. The war in Iraq cost the US government $2trn. If that money had been spent on — well, almost anything else, let’s face it, it would have been better. If it had been spent on a renewable energy infrastructure, we might not need to have this conversation. Do you really think that, in forty, fifty, sixty years’ time — if we don’t address this problem — things will be any better? A Middle East that suffers from intense heatwaves and droughts, and sits on the increasingly rare and precious fossil fuels that the West depends on? Does this seem like it will be a more or less stable situation? Renewable, sustainable energy is not just an environmental issue: it’s a national security issue. Some of the best investment came in response to the oil shocks in the 70s and 80s; it seems that as long as the price is kept low, people forget about how harmful this dependence is economically and politically as well as environmentally. There are always going to be some people for whom the ‘future-generations’ argument doesn’t cut it — but perhaps realizing how bad the situation could get within our own lifetimes, without action, will galvanise people into action.

If our species is going to have any kind of future, we need to make this transition to a more sustainable way of life. It’s as simple as that. We have the technology, or we can develop it; it’s getting better all the time. Humans have achieved incredible things — when we put our minds and resources towards them. The fight against climate change should be no exception.

I finally would like to direct you all to a good resource in this — alongside the David Mackay book whose praises I sing all the time. Drawdown is a book and website that goes through the most effective strategies at reducing carbon emissions in a cost-benefit kind of way, ranking them in terms of effectiveness. There are some surprising entries on the list that you might not have thought of, and many of them — particularly the energy efficiency measures — you can make in your own lives to make a difference. For the others, you can write to your legislators and let them know that this issue is important to you: find other like-minded people and organise to lobby for these things. If politicians only care about the next election, and not the long-term consequences of their actions, we have to make this an issue about the next election.

We know what we must do. We know that it will be good for us. We know that it won’t be easy. The situation is very similar to me staring at the treadmill when I’m at the gym. The best thing to do, in both cases, is just to start.

Thanks for listening etc.