Will Steffen – TRANSCRIPT
Thanks very much, Steve. For those of you who are expecting a talk on climate change, actually thankfully, you won’t get it.
I’m going to talk about this rather broader context, broader term which puts climate change in a much broader context. That’s the term of “Anthropocene.” Now, for those of you who studied Geology or even watched Hollywood films, you know that geologists like to look at earth history in terms of periods, eras, or epochs, or something. You’ve probably heard of the Pleistocene, many of you. Those of you who have seen the famous Hollywood film certainly know the Jurassic era, Jurassic Park, but there’s a group of us now who are proposing that the earth has actually entered a new epoch at least, perhaps even a new era which is a more substantive term, and that is the Anthropocene.
As the name indicates, Anthropo refers to us. It refers to human beings. Unlike the previous eras in earth’s history which were marked by meteorite strikes, big changes, for example, in plate tectonics or something like this, this is a biological species, ourselves. We are pushing the planet into a new and perhaps, somewhat frightening geological, as well as biological era. Let’s get started with what the Anthropocene actually means.
I really like to show this graph up here. This is some data taken from an ice core in Antarctica. The famous Vostok Ice Core. That’s a Russian station by the name of it but many people don’t know, this ice core comes from Australian territory. This is from the 42% of Antarctica which we claim.
Now, this particular record goes back nearly half-a-million years. The red line in the middle is a proxy for temperature. How temperature changes through the time.
The important thing is entire human history is encompassed in this ice core. Fully modern humans, Homo sapiens, evolved around 250,000 years ago. You see that in the middle, we evolved in Africa. Now, for well over 90% of our time on the planet, you see that stretched out, we are hunter and gatherers only. Our genetic code is wired for hunting, and gathering, and living in small groups of up to 200 or 300 people.
We live in a quite different world. The beginning of agriculture only occurred at the very end of the record at a warm period. Notice how the ethoxylates in a beautiful rhythmic pattern, much likely human heartbeat between long cold periods and short warm periods, but the present one period is unusually long – I’ll get to that in a moment – which means that it’s given us a bit of time to break out of the hunter and gatherer mole. It’s only during this last 10,000 years that we’ve had agriculture and so on. Let’s look at that in a little bit more detail.
This is another ice core, and this comes from the opposite end of the planet. That other one was down here in the south in Antarctica. This one comes from Greenland, not far from the North Pole. It’s actually a much shorter time period. It lasts 100,000 years.
It captures the earth as the temperature, and this blue line is another proxy for temperature as it’s sliding in to the most recent ice age. There are a lot of spikes that you see in the northern hemisphere that you don’t see so clearly in the southern hemisphere, but we won’t be concerned about those here. We’re looking at common trends across the earth. Now, we unpack what has happened to us as a species in more detail. The first successful migration of fully modern humans out of Africa was about 85,000 years ago.
You see that there was a dip in temperature which means that sea levels dropped. It was easy for humans to migrate out of Africa, and they did. They went around the Arabian Peninsula, moved on through around the Indian subcontinent through the Indonesian archipelago. The earth was getting even colder through that time. Sea level is dropping even further.
We were connected to New Guinea, Tasmania was connected to the Mainland, and so on. The first wave of fully modern humans ended up here. In fact, it branched at the very end between New Guinea and Australia. Indigenous Australians are the endpoint of the first wave of fully modern humans out of Africa. They left groups of people all the way long, and indeed some continent, and so on.
Some of those later on then, set migrations up from South Asia into Europe. Now, those of us of European descent, and I’m primarily of European descent, I can trace my mitochondrial DNA. In fact I can trace mine back to that second red here or about 33,000 years ago, but I come from South Asia originally. Basically, all of us who are Europeans come originally from South Asia and originally from Africa. Again, look at this ice core record about 10,000 years ago, the earth became very much steadier in climate.
It was warmer, carbon dioxide was much higher, plants were growing better, sea levels are rising too starting to isolate us again. As the sea levels rose by 120 meters between the bottom of the ice age and that period then. The geologists actually have a name for that 10,000-year period with a blue line. It is zero which is a simply a reference temperature, and it stays there pretty steadily. That’s called the Holocene. That’s still the official epoch that the earth is in.
We’re suggesting now that we’re moving out of that epoch, out of the Holocene and into the Anthropocene. What has happened during that 10,000-year period of unusual warmth, and reasonably steady climate, although rainfall has gone up and down through that period? First of all, about 10,000 years ago, we saw the beginning of agriculture. Very interestingly, it appeared pretty much simultaneously at four different places on the planet. Most people associate it with the Middle East, with present day Syria, Mesopotamia, and so on.
That was one of the places, but one of the other places was just next door to us, and that was New Guinea. The New Guinea also invented agriculture about 10,000 years ago. The other two were in the Americas; in Mesoamerica, and up along the East Coast of North America, pretty much simultaneously. Then, we started living in villages because we had a food supply. We grew towns and cities.
We developed civilizations in Africa like in Zimbabwe and the Americas and, of course, the ones we study in school in Europe like the Romans and so on, and the Greeks before them. All of this occurred in this unusually warm and stable 10,000-year period. Now, are we set to go into the next ice age? Absolutely not. By a quirk of the earth’s orbit around the sun, this nice steady period of 10,000 years was stretched to at least 20, and perhaps 30,000 years if we don’t interfere with it. Humanity is really set for a very long period of equable climate on the planet in which to further develop.
However, this is where the Anthropocene comes in. Let’s see what’s been happening. We have been changing remarkably through this 10,000-year period but something different happened around 1750 to 1800. Now, we’ve always affected the environment. In fact, there’s some evidence that other indigenous Australians, as well as Asians, and so on led to the extinctions of some very big fauna.
Giant kangaroos, and wombats in our case, wooly mammoths and so on in Asia. They’re still debating the scientific community but there may be a human imprint there. We certainly learned to use fire and modified landscapes, but we basically relied on our own energy and the energy of animals that we might be able to use, and a little bit of wind and water, but around 1750 or 1800, something new occurred. We were able to access fossilized energy that have been built up over millions of years under the surface of the earth, coal, petroleum products, gas, and so on. That led to an absolute unleashing of what we call a human enterprise.
What we tried to do here is to look at the human enterprise from 1750 to pretty much the present, and look at several different aspects. We looked at population going from less than a billion up to between six and seven billion now. Total real GDP, direct foreign investment. They capture aspects of the economy. Damming of rivers, water use, fertilizer. These are resources uses. Look at how the values are going up, and up, and up in each of those. Urban population going up. Paper consumption. We have to have an indicator for globalization.
What better? We heard a bit about Coca Cola. That would have been a pretty good one too, but we went from McDonald’s restaurants, and there you see in terms of the numbers, thousands of McDonald’s restaurants around the world. Then, we looked at transport and communication. There is motor vehicles. We all live with motor cars. We accept them as normal. There were virtually none before 1950 around the world. Communications, telephones, that’s landlines. They are disappearing now in favor of mobile phones.
International tourism. Now, notice something remarkable about those graphs, and that’s the year 1950. A second event happened in 1950. It was, as you probably know, the Second World War, which not only knocked off quite a few people although you don’t see much of a bleak in the population. What it did do is break down old institutions, quickly economic institutions, old ways of thinking, and it led to a massive increase in connectivity, networking financially, information flows and so on. That led to what we call a great acceleration, the period from 1950 to the present.
Some of the things we take for granted, foreign direct investment. We just heard that 25% of our mortgage money is actually brought in from overseas. We are tightly linked with the global financial system as we found out, but looking in at national tourism. Look at motor cars. Look at McDonald’s restaurants. They virtually didn’t exist before 1950. We’ve seen a massive change in the way we organize ourselves, in the way we lived since 1950. Those of us who are studying the Anthropocene say that the beginning was probably around 1750 to 1800 when we started accessing this new energy source, fossil fuels, but stage two of the Anthropocene started in 1950 when we reorganized ourselves, population exploded, economy exploded, resource use exploded, and so on.
Why do we say this is really a new geological epoch? You actually have to prove that this is doing something to the earth, and indeed we do. In the very same scale from 1750 to 2000, we looked at what’s happening to planet earth. The top three graphs of the famous greenhouse gases, the one in the upper left is carbon dioxide. I showed you that elegant Vostok Ice Core, CO2 going up and down. During the time we’ve been on the planet is isolated between 180 and 280, and it’s maxed out at 300 parts per million. It is not 3872, I believe, parts per million, and going up at about 2 parts per million per year unprecedented in the geological record.
There’s nitrous oxide, methane through the greenhouse gases. Depletion of ozone in the stratosphere rocketing up again since 1950. New chemical compounds. These next two, northern hemisphere sulfurous temperature and great floods are the only two climate ones on this set of 12. That captures climate change, but look at direct human impact on ocean ecosystems, coastal zone, coastal barge and chemistry.
That’s nitrogen flowing through the coastal zone. Look at the massive change in the nitrogen cycle. You see 1950 again appearing there. Direct impact on land, loss of tropical forest and woodland, again going up. Amount of domesticated land, that’s land that has been completely made over and used for crop plantation, forestry, and so on again going up.
Biodiversity, the extinction rate shooting up again. This is a strong evidence that we have left the Holocene. In each case, except perhaps yet for temperature, we have left that envelope of environmental stability which typifies the Holocene. Now, this is the case we’re putting forward to the Geological Society of London which is the body that actually decides what era or epoch in earth history we are in. They formed a working group that is studying this now.
You may find in a couple of years that there will be an announcement made that the earth has officially left the Holocene and entered the Anthropocene. This is some of the evidence we’re putting forward. Interestingly, climate change isn’t the strongest argument. The strongest argument is biodiversity. Why is that so? Many of the earth’s epochs are defined by sharp changes in the fossil record.
Something happened to the biology of the planet. A classic example when the dinosaurs went extinct relatively rapidly. Now, it’s thought that that was caused by a meteorite strike on the planet and so on, but in many cases, periods of earth history are defined by abrupt changes in the biological part of the planet. We’re seeing it now. Extinction rates are 100 to 1000 times background level.
That’s due to us, of course. That unmasked even more changes in terms of moving species around the planet, range, contractions of many species who aren’t extinct yet but they’re functionally extinct and so on. That’s expected to increase by another factor of ten this century as climate starts to shift. What do we do about this? Do we accept the Anthropocene and try to live in it or can we recover the Holocene in some way or another? This brings me to the last point I want to make. There’s a group of us who published a paper in Nature a couple of years ago, about a year-and-a-half ago.
We’re proposing something that we call “Planetary Boundaries.” It’s a very simple concept. We all understand boundaries. This block here obviously has a boundary right behind him. He doesn’t want to step across that because it won’t be very good for him. He has to respect that. We teach our children boundaries. We don’t let them play on busy streets. We keep them away from other dangerous things. We accept boundaries as important parts of our life but we don’t do that yet at the planetary scale.
We think it’s time to start thinking about planetary boundaries. How am I actually to find planetary boundaries? What we attempted to do was to look at how the planetary system actually works? How does our environment function? Where are parts of the planetary environment that could shift? Perhaps, even shift abruptly or irreversibly if we push them too hard, if human activity pushes them too hard? Now, we can look the ice cores and we can look at the other so-called paleo-evidence, and it gives us some really good clues because back in the earth’s history, we’ve seen abrupt shifts and we’re starting to get an inkling of why those abrupt shifts occurred and we may be pushing the planet towards some of those which would not be healthy at all for Homo sapiens or for our societies?
We think we’ve defined at least initially nine processes or parts of the earth’s system that we need to respect. One of them, only one out of the nine is climate change. What’s our control variable there? We chose carbon dioxide. We believe from examining all the evidence of the past, we shouldn’t go above 350 parts per million CO2 to stay within the safe Holocene type of environment.
I just mentioned where we are now, 3872. We’re in overshoot. Two others we believe are in overshoot. One of them is the nitrogen cycle. We actually now fixed more nitrogen. By “fixed,” I mean pulling nitrogen out of the atmosphere, unreactive nitrogen and through industrial processes, turning it into reactive nitrogen, spreading it across landscapes. We needed a course to grow food. The food actually takes up a small percentage. The rest of it moves out as pollution, polluting ground water, polluting the atmosphere, polluting coastal seas.
Third one is the one I mentioned, right biodiversity loss, but there are other important things too, ozone, depletion, aerosol loading. That’s pollution. How far should we go there? We’re acidifying the ocean. Where should the boundary be there? Global freshwater use. We’re using nearly half of the water now that flows to the ocean.
There’s not much left for the rest of the species on the planet. Where should we draw the line? What defines a Holocene environment? I think this is one of the most active areas of research. We’re only beginning to understand where we should try to put boundaries but we believe it’s an important concept because once you define where the boundaries are, then it defines a safe operating space where humanity can maneuver. We can talk about equity issues, we could talk about economic growth and so on, but we are biological species, and we live on a planet, and we need to respect the boundaries of the planet itself intrinsically sets for us.
In summary, we have moved into the Anthropocene. Whether we should stay there is a decision we should talk about. Talk about as a global community because I think in the end, the risk associated with the Anthropocene will really push us past some limits and like those earlier civilizations I showed you on the first slide, there is no guarantee civilization lasts forever. The Romans aren’t around nor the Mayans. We might not be either unless we start thinking globally, as well as locally. Thank you very much.
Related Posts
- How to Teach Students to Write With AI, Not By It
- Why Simple PowerPoints Teach Better Than Flashy Ones
- Transcript: John Mearsheimer Addresses European Parliament on “Europe’s Bleak Future”
- How the AI Revolution Shapes Higher Education in an Uncertain World
- The Case For Making Art When The World Is On Fire: Amie McNee (Transcript)