Timber construction is a silver bullet for climate change

Hans Joachim Schellnhuber has spent 30 years at the forefront of scientific research into the effects of runaway climate change. Now he believes he has the cure: make buildings – lots and lots of them – from wood. ‘Everyone says there are no silver bullets but I guess we found one’, the 72-year-old physicist tells me via Zoom from his office at the Potsdam Institute for Climate Impact Research, which he founded in 1993 and led until 2018.

The premise is straightforward. Cutting greenhouse gas emissions will not keep global warming within the target of 2ºC. Some help comes from natural biosinks – the seas and forests that take up CO2 – but they are overwhelmed, so we need artificial biosinks too. We have 1bn ha of degraded land that could be replanted with trees, but as forests mature they start to emit as much as they absorb. That’s where the buildings come in. By harvesting timber to make cities, we can lock up vast quantities of carbon for the long term while promoting forest growth. Build enough, and global warming goes into reverse. 

How much timber are we talking about? By planting and maintaining 500bn trees, and constructing 2bn timber buildings over a couple of centuries, the atmosphere could be returned to a state not seen since the Industrial Revolution. ‘Of course it will not happen this way,’ Schellnhuber concedes, ‘but if only half of that is achieved we can still save the world.’ 

To help catalyse that transformation Schellnhuber has founded Bauhaus Earth. Formally launched in 2020, the think-and-do-tank is jointly led with architect Philipp Misselwitz. Earlier this summer, its first big conference took place in the Vatican. (Schellnhuber is climate advisor to Pope Francis, as well as European Commission president Ursula von der Leyen, who gave the keynote). Pritzker Prize-winners Shigeru Ban and Francis Kéré were among a starry cast of architects in attendance. 

This new role as a passionate advocate for climate-friendly construction is just the latest twist in Schellnhuber’s varied career. ‘People boast that they made a perfect design of their life trajectory,’ he says. ‘This is rubbish. We are all driven by accident or incident.’ Growing up in Bavaria, Schellnhuber – known as John – had a love of nature and broad interests in culture, philosophy and politics. Excelling at mathematics, however, he pursued an academic career in theoretical physics. ‘It sounds arrogant,’ he says, ‘but everything else seemed too simple’.

Working at the University of California he was drawn from quantum mechanics into the emergent field of chaos theory. ‘Today it has a more respectable name: non-linear dynamics of complex systems’. Back home in the late 1980s he began to receive requests to model complex phenomena in the natural world, from tidal flats to the consequence of Gulf War oil fires. Another ‘accident’ nudged him fully into environmental work. After German reunification the scientific landscape of the DDR had to be reorganised, and an impressive Potsdam campus was earmarked for climate research – a subject that was just beginning to creep onto the political agenda.

Schellnhuber was invited to be founding director. ‘Data was scarce but I instinctively felt this is the defining issue of the 21st century’.

Initially, however, there was little sense of urgency. ‘It felt like there were some big threats out there,’ he recalls, ‘but that they were so far away we had time to avoid them.’ That confidence did not last. Helping Angela Merkel prepare to host the first UN Climate Change Conference, COP1, in 1995, Schellnhuber began to reframe the climate question in terms of outcomes to avoid at all costs. ‘In this way I discovered the idea of ‘tipping points’ in the earth’s system’. Our planet’s vital organs, such as the Antarctic ice sheets, Indian monsoon or the Gulf Stream could suffer irreversible harm, with devastating knock-on effects. 

The first IPCC report in 2001 estimated that these might occur at 6ºC warming. By the time of the Paris Agreement in 2015, Schellnhuber’s ‘tipping points’ were central to its argument, and his ‘guardrail’ figure of 2ºC accepted as the safe limit. ‘But we know that danger really starts where we are, at 1.2ºC’, he says. ‘We will probably lose all coral reefs at 1.5º. We already have a weakening of the Gulf Stream. So now it is really time to panic’.

Warming at the upper end of the predicted range would mean the end of civilisation, as coastal cities vanish and large regions of the earth become uninhabitable. ‘Nobody should imagine that you could manage the migration of three billion people without bloodshed and the collapse of social systems’. Until quite recently, he says, such suggestions were ‘taboo’. Today there is some variety of opinion among colleagues about timescales, but the basic analysis is broadly accepted: ‘Concern has increased exponentially over the last decade’.

Although the message is alarming, it’s delivered without apparent sensationalism. In conversation Schellnhuber is matter-of-fact, with a wry sense of humour and a nice turn of phrase. While public roles have sometimes required opinions on political issues to be carefully worded, he remains refreshingly candid. ‘Scientists still have the privilege to speak freely,’ he says. ‘I never felt that my three roles as a basic researcher, a policy advisor and a communicator required a split personality’. His ability to translate complexity into simple concepts – ‘tipping points’ and ‘carbon budgets’ – has been vital in broadening public understanding. ‘It’s OK to express yourself in simple terms if you’re right’, he says, ‘but that’s the most challenging of tasks.’

Timber as the ‘silver bullet’ is another easy-to-grasp concept, though perhaps lacks a suitably snappy catchphrase. Schellnhuber is using ‘the forestry-construction pump’ and ‘the co-transformation of built and planted environments’. 

‘It’s a narrative based on human agency, which is why people love it’, he says, ‘but it’s founded on very sober analytical work’. That began a few years ago with the realisation that catastrophe loomed. ‘I looked into geo-engineering – extraction of carbon through chemical treatments or from the air – and it’s all crap; expensive and dangerous’. Instead, he says, carbon can be converted into things of real value. And unlike visions of sustainability predicated on scarcity, his offers abundance. ‘The more you do, the better’.

That’s not to say we should replace existing buildings. Retrofit makes sense if bio-materials are used. But there’s a misconception that Europe is now ‘complete’. Germany needs 400,000 new homes every year. Wood should be the default option. The real prize, however, is in the Global South, where perhaps 80% of buildings needed in the coming decades don’t yet exist. ‘If they build as we have done, it’ll be the end of our climate story’. 

There are, of course, enormous challenges to overcome – technical, industrial, cultural – all of which Bauhaus Earth aims to address. The impetus behind it was another ‘accident’, says Schellnhuber: ‘2019 was the 100-year anniversary of the original Bauhaus. I thought that if all those people were reborn they would see the world going down the drain, and do something about it.’ 

For Schellnhuber, the Bauhaus provides a powerful example of both cross-disciplinary collaboration and design addressed to social purpose. We are at the end of the age of ‘extractivism’ – the fossil-fuel-based era that has shaped our political and economic systems. He believes that building more sustainably should be indivisibly linked to commitments to equity, justice and inclusion, and to beauty. That’s why the Vatican conference was called Reconstructing the Future for People and Planet. 

Bauhaus Earth has been busy on other fronts, too. There are plans for a base in Potsdam; a temporary pavilion should open in 2023, preceding a permanent structure. A material research lab will soon open in an old Berlin gasworks. Others will follow. Also completing this year is a new Barcelona Pavilion, constructed on the site of the original. Nascent initiatives include a successor to Germany’s International Building Exhibitions, working with partners to showcase innovative bio-construction in different parts of the world. It aims to show and seduce, not just tell.

To be effective, such ideas need to trickle down to parts of the construction sector where architects have little involvement. Is that realistic? ‘I tend to think in terms of ecosystems’, says Schellnhuber. ‘What we do can infect others. Most processes in nature and society are highly non-linear.’ The original Bauhaus is a case in point. 
There are promising signs that Bauhaus Earth could exert an outsize influence. This month, Schellnhuber will address the G7’s sustainable urban development ministers.

Already, his concept has prompted political action: inspired by Bauhaus Earth, Ursula von der Leyen has instituted the ‘New European Bauhaus’ – an integral part of the European Green Deal to make the EU climate neutral in 2050. A good start.

Going on past behaviour Schellnhuber has low confidence that we will do what’s needed to avert disaster, but remains positive. ‘Of course it is a tall order, but we are hopefully a part of a new global movement’, he says. ‘We can live better, and turn the built environment from climate villain into hero. I cannot give you a better story than that’.