In Paris, France, last year, governments agreed to confine global warming to well below 2 degree Celsius. What’s the driving force behind this?

‘As Martin Luther King put it, “the fierce urgency of now”. We probably have underestimated this urgency to some extent, even in the scientific community. Years ago, I introduced the concept of so-called tipping elements. This refers to critical components of the earth system like the Greenland ice sheet, the Amazon rainforest or the Indian summer monsoon that could at some point of continued perturbation be tipped from one state to another – we call this highly non-linear behaviour. Crossing critical thresholds would cause comparatively abrupt and perhaps irreversible environmental changes. And we know that beyond 2 degrees global warming the risk of tipping increases. Now there is new evidence based on historic reconstructions that shows climate sensitivity is probably higher than estimated in the latest report of the Intergovernmental Panel on Climate Change. This could mean we can emit even less CO2 if we want to stay within the temperature range agreed to in the Paris Agreement.

‘If we keep doing what we’re doing so far, in a business-as-usual scenario, this could mean about 5 degrees warming by the end of the century. It’s not hard to imagine that this could mean the end of the world as we know it. The changes we’d face would be profound. So we seem to be at a highly critical moment in our time where we have to get almost everything right in order to avoid most severe consequences. This worries me, especially when I look at recent developments like in the United States with a President-elect Donald Trump, possibly planning to leave the Paris Agreement behind. He will probably also invest trillions in building roads and other infrastructure with concrete and steel, which will churn out billions and billions of tonnes of additional CO2. This is the tragedy of many civilisations, as can be seen in history. When societies got into trouble, far too often the response was not to change the system, change the paradigm, but more of the same.’

How do we go about changing the paradigm?

‘What we need is a roadmap towards decarbonisation, with decadal steps bringing down emissions to almost zero by 2050. Because that is the only chance we have to stay within the 2 degrees limit, even though it would probably not be enough to keep warming below 1.5 degrees. But if you want to go down that road by mid-century, that means that by 2020 emissions globally have to peak. That may sound like a tremendous effort, but it also means turning back to many solutions we already have. It means repairing the European Emission Trading System and boosting efficiency measures everywhere. People have kept on talking about the low-hanging fruits, but they never pluck them. Now is the time.

‘In the next decade, until 2030, there are two essential shifts that should happen from my point of view. A phase out of coal-fired power stations, completely and worldwide. That means stopping building new ones, but also shutting down some of the existing ones. And we should get over the combustion engine in automobiles, because it is about time to completely replace it with much smarter alternatives.

‘Then, in the decade after that, we also need to have a number of major breakthroughs, technology breakthroughs. Think of super-smart grids connected by super-conductivity cables. People are working on this already, as this could transport electricity over long distances without any losses. Think of cities not being built anymore with concrete or cement, which is highly climate-damaging. These might be cities built from wood again, which was dominant over thousands of years, next to stone and clay of course. Already, in a city like Berlin (Germany), there are five-storey apartment buildings mainly constructed from wood. Young entrepreneurs are working on very innovative ways to treat wood to make it more flexible and fireproof. Building in wood would help us… even (reduce) carbon (usage). While cement production is a huge source for CO2, wood can be used as a carbon sink, absorbing and storing CO2.

‘And that is the other, much brighter side of the coin. If we embrace this challenge and turn climate stabilisation and a sustainable future into the new narrative of modernity, not only would this be a fantastic project for humankind, creating new jobs, it would also shape a world of new life opportunities, new cultural development, and so on. We still have the choice, as we are standing at the crossroads. This could give our modern times a new meaning, enabling us to use all the available potential, whether it is intellectual, whether it is physical, whether it is resources. So it is a very interesting point in time, we either go for the bright side of a sustainable future, or we might go for the dark ages again.’

For climate research, where should the focus be as the EU prepares its next funding programme to follow on from Horizon 2020?

‘In order to get a real grip on the climate problem we need a strategic approach, something like an Apollo project, that focuses all available resources and potentials on a common goal. You would need some kind of a roadmap, mapping out… the low-hanging fruits, like energy efficiency, as well as technological innovations in strategic areas like new material for construction, also carbon-negative technologies. But there are many other areas as well with great potential, like agriculture. You could very simply avoid a lot of emissions from agriculture by no-tillage approaches where you do not plough the soil.

‘Commissioner Moedas (the EU Commissioner for Research, Science and Innovation) has set up this new high-level panel for European decarbonisation pathways… and I am chairing it. And there, my intention is to work out precisely such a roadmap. Not a narrow-minded, technocratic document, but an open plan with a number of important milestones. And here is the important thing. Innovations don’t need to be only physical, chemical or whatever. There are many social innovations that also help us to go for a more sustainable world.’

What kinds of social innovations do you mean?

‘Let me give you an example: the carmaker BMW told me once about their electric car, the i3. I drive an i3 today as my private car, but I’m one of very few people who own one. What did the company do? They set up a collaboration with partners including the City of Berlin for a very popular Berlin vehicle-sharing scheme. You can find available cars on your smartphone, and they have created a fleet of these i3 cars which you now find everywhere on the streets of Berlin. The city will support this by reviewing their public parking-space policies.

'People have kept on talking about the low-hanging fruits, but they never pluck them. Now is the time.' Prof. Hans Joachim Schellnhuber, Potsdam Institute for Climate Impact Research, Germany

‘The biggest social innovation might be to set up some kind of transformation fund - like the sovereign wealth fund in Norway - where you strategically invest in new infrastructure, and where the funding could come, for example, from a carbon tax or trading scheme. Some countries already have carbon taxes, and if the revenues would go directly into a transformation fund earmarked for climate innovations, this would be a completely new way of dealing with the climate challenge. So from simple individual behaviour up to fiscal institutions, you can go through a whole series of possible innovations.’

You have been credited for coming up with the 2 degrees threshold that the world is working towards. Yet it is becoming clear that the climate could be more responsive than we thought, is this level low enough?

‘We have not completely understood the climate system yet, and particularly the non-linear behaviour associated with tipping points should be researched further. Many scientists tend to be a bit conservative, staying on the safe side, avoiding what could be misunderstood as alarmism, thereby sometimes underestimating the dynamics. Only recently, I published a paper together with colleagues in Nature Climate Change about critical thresholds when you turn up the heat globally. The question is, when do we reach these critical thresholds? There are still some uncertainties but, as it turns out, limiting warming to 2 degrees will not be enough to avoid all tipping points. The tropical coral reefs will probably completely die back, even if we limit global warming to 2 degrees Celsius. The Greenland ice sheet might also be at risk.

‘So 1.5 degrees clearly is the better target, but I think it could only be achieved by overshooting the available emissions budget temporarily and then later coming back to within the budget range - which means you have to work with substantial negative emissions, a very difficult concept. I think it could only be done if we turn global agriculture into a carbon sink and actually build all our future cities from carbon-negative materials. That is the only scale where we could achieve it, so the answer is, 1.5 would be much better in terms of climate impacts than 2 degrees. But 2 degrees already requires an industrial revolution at the planetary scale. In contrast, I think 1.5 degrees requires almost a miracle. But of course sometimes miracles do happen.’

You say miracles do happen, but you’ve also mentioned the drastic changes that need to take place such as getting rid of the internal combustion engine and revolutionising agriculture and the way we build cities. It seems like an enormous challenge.

‘Mind-boggling, yes. But the crazy thing about it is, these things can be done. People pursue nuclear fusion, which might be a benefit in the end, but it is a tremendous challenge with no end in sight so far. Yet it seems to be ok for the EU to pour money into that endeavour, and I accept that because it is an exciting intellectual enterprise, even though it will probably not save the world. However, we already have a perfectly working powerful fusion reactor – the sun. Solar energy comes without any cost, it is absolutely safe. We just have to harvest it. We do not have to bend the laws of physics to make use of the sun and to use wood as a carbon sink and so on. So, in a way, our society is in a strange state of schizophrenia. On the one hand we go for highly, highly utopian technologies and are willing to fund them. At the same time, we say that things that are already proven in principle are impossible to achieve, and this has to do with vested interests of course, and also with human inertia. People would rather go for the fairy tale that we will drive the whole economy by fusion energy by 2050, which is of course impossible, but at the same time they tell us that it is absolutely impossible to run a country like Morocco from solar energy.

‘I am from Germany, a country with lots of renewable energy production. But if you conduct an analysis of the sunshine potential of Germany, it is comparable to Alaska (US). So how much easier would it be for Italy and Greece and the United States of America, let alone Africa, to run their countries on sunshine? I think we need to get rid of all the myths that are, in a way, congesting our brain, and once we have done that, yes then the answer is I think it is achievable still.’

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