Will Steffen is an Earth System scientist. He is a Councillor on the Climate Council of Australia that delivers independent expert information about climate change. He is also an Emeritus Professor at the Australian National University (ANU); Canberra, a Senior Fellow at the Stockholm Resilience Centre, Sweden; and a member of the Anthropocene Working Group. From 1998 to mid-2004, Steffen was Executive Director of the International Geosphere-Biosphere Programme, based in Stockholm. His research interests span a broad range within Earth System science, with an emphasis on sustainability and climate change.

On Tuesday, February 22, he gave the lecture "The Anthropocene: Where on Earth we are going", as part of the Europaeum Winter School held at UPF, focused on Planetary Wellbeing.

Your conference at UPF will be about where we are heading as a planet. So the question is, where are we going?

I think we are going in the wrong direction and we are doing it in many different ways. The general topic of the talk will be the Anthropocene, which has a significant impact on the Earth. What we call the Earth System, the planetary system, is changing at an extraordinarily rapid rate, moving away from the stable Holocene state, the state in which the Earth has remained for the last 12,000 years, and which has represented the only time that humans have been able to develop agriculture, villages, cities, complex societies, and so on.

When we look at the climate system, everyone talks about it, we see that there is an accelerated increase in climate destabilization, the temperature is rising, extreme events are getting worse ... On the other hand, when the focus is on other aspects of the Earth System, like the biosphere, we see that we are also degrading it at an increasing rate. We are losing important ecosystems, such as the rainforest, or animal extinction rates are rising.

We are going in the wrong direction and we are doing it in many different ways. What we call the Earth System is changing at an extraordinarily rapid rate, moving away from the stable Holocene state, the state in which the Earth has remained for the last 12,000 years

So when we look at the overall structure of the Earth System and see how it works normally, we see that we are disrupting it in many different ways. The talk will address these issues, how we are changing the Earth System, what has driven it, and what we need to do to stabilize it.

You usually talk about tipping points. When one is reached the others are strengthened and the warming of the planet. Could you explain some of these tipping points?

The tipping points are basically of three different typologies. They are large chunks of ice near the poles that can melt, they are large ecosystems on which we depend - the Amazon rainforest could be a good example of this - and there are ocean and air circulation systems.

To give you an example, melting all the ice on the Greenland Ice Sheet in the North Atlantic would mean a 7-meter rise in sea level. This would be a catastrophe, given the large number of people living near the coast. It is currently beginning to melt, and it is doing so in two different ways.

On the one hand, it is losing some of its outlet glaciers, the ice begins to move and break and ends up in the ocean. But at the same time, it is melting from its surface, because warming, at high latitudes around the Arctic, is even more pronounced than the global average. As the surface melts, it gets lower and enters into a warmer climatic zone. This accelerates the ice melting. This is how you get to a tipping point. There comes a time when you reach a point of no return, a point where even if you manage to stabilize the climate, we will not be able to recover it. This is a tipping point. Pushing a system far enough, a system that has its own built-in feedback mechanism, makes the change unstoppable and the system completely changes.

Another example would be the Amazon rainforest. As deforestation continues, you lose the ability of the forest itself to evaporate water. Half of the rain that falls on the Amazon is recycled water from the forest itself. The system is simple: it rains on the forest, the trees take up water from the ground, the water evaporates back to the atmosphere and it rains again. But when you start to shrink the forest by converting the land to pastures and meadows, less water evaporates. If deforestation continues, there is a time when there is no going back because you will never get the water and moisture you need to regenerate.

We've analyzed nine or ten of these tipping points, and they're all starting to move in the direction of the tipping point. In addition, these tipping points are connected, the ice of the North Pole is connected to the rainforest in Brazil

We've analyzed nine or ten of these tipping points, and they're all starting to move in the direction of the tipping point. In addition, these tipping points are connected, the ice of the North Pole is connected to the rainforest in Brazil.

Ice floats in the Arctic Ocean and shrinks due to global warming, so more and more dark (ice-free) ocean water is exposed during the summer. The water absorbs more sunlight and therefore accelerates the warming and the ice shrinks even more. The accelerating warming increases melting of ice on Greenland, and this delivers more freshwater to the upper part of the Atlantic Ocean, which, in turn, slows down the north-south circulation of the ocean.

What does it ultimately mean? So, this change in circulation is reducing the rainfall on the Amazon and, with the increase in deforestation, we are pushing the forest towards the tipping point.

This is what we call a tipping cascade, like a domino effect. The worst case scenario is to trigger a few tipping points because then we can lose control of the whole system, moving to a very different state of the Earth System as a whole, a state much harder for us to live in.

You also talk about planetary thresholds and the concept of hothouse earth. What does it mean? Could you give us some concrete examples of what human life might be like if this happened?

What it means is a very unstable Earth. This tipping cascade, if we really start it, is the process that takes the Earth system out of our control. The Earth will move to a much hotter state, with a 4 or 5-degree increase in temperature compared to the pre-industrial era, there will be huge changes in the biosphere, forests and prairies, with massive fires ... We are talking about big extinction events.

This scenario of collapse will cause a large drop in population worldwide, worsen human well-being, and so on. It is a global catastrophe and that is what we want to avoid at all costs. I know it’s scary, but we have to face the truth and explain that if we don’t take these threats seriously now, that’s the risk we’re taking for our children.

This involves a very large disruption at a rate of change never seen before in the history of the Earth, only comparable to when the meteorite impacted Earth 66 million years ago. My view is that human civilization, the society we know today, will not work in this kind of world. This scenario of collapse will cause a large drop in population worldwide, worsen human well-being, and so on. It is a global catastrophe and that is what we want to avoid at all costs. I know it’s scary, but we have to face the truth and explain that if we don’t take these threats seriously now, that’s the risk we’re taking for our children.

Are we already on a path of no return in terms of climate emergency? Have we finally lost control of our planet?

I don't think we've reached this turn of events yet. What we are saying is that different tipping elements are moving towards a tipping point. The problem is, we don't know exactly where this tipping point is. And we'll never know, unless we get there, which is pretty stupid.

Therefore, it is a matter of risk. How much risk are you willing to take? My estimate is that if we can achieve the most ambitious goal agreed in Paris, a maximum of 1.5 degrees of warming, which is extremely challenging, now we all know, this would minimize the risk of starting this cascade. When we start approaching two degrees and if we go beyond two degrees, the risk increases very quickly and we can start a tipping cascade. That is why the climate goals of Paris are so important.

It seems that the climate conferences, the COPs, are not solving the problem.

No, they don't work. The latest was COP26 in Glasgow. You can go back 26 years and watch the first climate conference. And you can see how human emissions have been increasing and increasing over the last 26 years.

There is no evidence that any climate conference has had a positive impact on this emission curve. That is the sad truth. And that must change

There is no evidence that any climate conference has had a positive impact on this emission curve. That is the sad truth. And that must change. If it doesn't change in the coming years, I don't think we will meet the Paris goals. Time is up.

How can we avoid this scenario? What are the minimum actions that humanity needs to take to stop this process?

I think we need to take action, and we need to take action now: stop any new development of fossil fuels. There are already a lot of oil wells, coal mines, gas fields... and there are plans for large expansions, particularly of gas. These plans have to stop right now in every country. And that's not just what we scientists say, but the International Energy Agency says the same thing: we need to stop the expansion of fossil fields. Doing so next year would give us a good chance to get closer to 1.5 degrees, and with some removal of CO2 from the atmosphere, we can maybe even lower it to 1.5 degrees. So the first step is to stop the expansion of fossil fuels, and that has to happen now.

But I think the only way for that to happen is for the people to rise up against their governments. Demonstrations may be needed, perhaps people taking to the streets, or trying to stop this expansion directly, in person, by going to specific places. Civil disobedience. Only then will we get the changes we need in time.

We have to challenge the system. We have to take it down and build a new, much better system

And hopefully, change some government and corporate people will help us change the current path. Here in Australia, we are a major exporter of fossil fuels. But we have elections in a few months and there has already been a rise in terms of independent people running in parliament who say we don't like this, and they are growing in popularity. So maybe we'll have an ”election revolution” down here. The independent candidates are geting a lot of support. We will know in April or May, when the elections will take place.

We have to challenge the system. We have to take it down and build a new, much better system.

There is a feeling that young people are much more aware of these problems and are pushing for them to be solved. Do you think something is changing? Could we send an optimistic message?

The optimistic message is that just as there are tipping points in the Earth system, there are tipping points in the social system. Things can change more quickly in a social system when people get fed up. And I can sense that this is happening. We are starting to see young people from all over the world,  along with the elderly, and also new industries coming in, renewable energy, getting more support...

Thus, it can be seen that underneath the system, which still supports fossil fuels, a movement is being created. Is it strong enough? Not yet. But it can change quickly. It needs to change quickly. It is no longer acceptable to burn fossil fuels. Exploiting fossil fuels is no longer acceptable. This is antisocial.

The optimistic message is that just as there are tipping points in the Earth system, there are tipping points in the social system. Things can change more quickly in a social system when people get fed up. And I can sense that this is happening

Social media helps us, young people help us, scientists help us. Each of us alone will not change the system, but together we can have the opportunity to push it to achieve this social tipping point and change the system very quickly.

At UPF, we have launched the Planetary Wellbeing initiative, which aims to cover the entire university in terms of research, teaching and knowledge transfer. Do you think that such initiatives can help solve the problem?

Absolutely, this is part of the social tipping point. These things have to happen. It is important that many new institutions join. New ideas are important.

All these different ideas, institutions, networks that are boiling, this is what we need to achieve this great point of global social inflection

I will give a good example that comes from a place near you, in Portugal. There is a legal expert named Paulo Magalhães, and he is developing the concept of "common home for humanity." And what he says is that the most important thing we have to protect is not the territories, but the integrity of the Earth System, our planetary home. So what he wants is a legal recognition of the Earth System. Not the physical earth, but the intangible elements, the circulation systems, the heat transfer, all the things that keep the planet habitable. Once this legal recognition is obtained, it will be possible to start developing laws and economic instruments that are based on a legal context.

All these different ideas, institutions, networks that are boiling, this is what we need to achieve this great point of global social inflection.