A new book by a Cambridge engineer and an Oxford theologian argues that our faith in technology to solve the climate crisis is distracting us from the uncomfortable truth: that saving the planet is neither a task for future technologies nor for world leaders alone. It is something all of us — especially those with comfortable lives — can and must do, now.

Promise the Earth: A safe planet in good faith, is co-authored by Cambridge’s Professor Julian Allwood and Oxford’s Professor Andrew Davison, and is published by Cambridge University Press. Together, the two researchers call for a rethink on not just how we can reduce emissions, but how we live, hope, lead, and take responsibility.

An engineer and a theologian may sound like an unusual pair, but the researchers say that solving the climate crisis is not just a scientific problem, but one of changing hearts and minds. The book alternates chapters on the physical, business and political options for climate action with chapters on the seven classical virtues: courage, justice, prudence, temperance, faith, love and hope.

“The scientists have been convinced on climate change for a long time, but motivation to change is not just a data problem,” said Davison, who is Regius Professor of Divinity at Oxford. “We’ve got to look at the world as it really is, and how it ought to be, and work out how to bridge that gap.”  

“We’ve told ourselves a comforting story, that innovation will arrive just in time and solve the problem,” said Allwood, who is Professor of Engineering and the Environment at Cambridge. “But if you look at the physical reality of how fast we can build things, the plans we have just aren’t going to work. The magic beans won’t grow fast enough. There is no knight in shining armour coming over the hill to save us.”

Allwood has spent decades researching the material limits of decarbonisation: the steel, cement, energy and factories required to build our infrastructure. Technologies such as carbon capture and storage or direct air capture, often presented as essential to reaching net zero, are growing far too slowly to make a real difference.

“Carbon capture was first deployed in 1972, but after more than 50 years, it captures less than one tenth of one per cent of global emissions – and much of that is used to extract more oil,” Allwood said.

Even if governments fully committed to clean infrastructure, Allwood said there is a hard limit to how quickly new systems can be built. “If we’re realistic about the rate at which we can construct things, then we won’t have the resources we’d like to have. If we’re going to solve the climate crisis and leave a liveable world for those who come after us, then we have to be realistic and enter a period which includes some specific restraints.”

Restraint is a word rarely mentioned in climate debates, where optimism or despair tend to dominate. But Allwood says it’s the most realistic path left: using fewer materials, travelling less, changing how we heat our homes, and recognising that our influence extends far beyond our individual carbon footprints.

“It’s not just about what you do at home,” said Allwood. “It’s your workplace, your community, the organisations you shape. We all have more agency than we think.”

Allwood’s collaboration with Davison began with a shared frustration: that a mountain of scientific evidence has not produced meaningful change. “More science isn’t going to convince people,” said Davison. “And even when people do understand, that doesn’t necessarily motivate the changes we need.”

Working with Allwood changed him personally, Davison said. “It led me to be disappointed in myself. I’d said all the right things about living green, but hadn’t changed as much as I should. It took writing this book to shift my behaviour.”

Flying is one example. As a theologian and academic, international travel had long been part of his life, and part of academic culture more broadly, but it’s something he’s recently changed.

“I haven’t flown for a holiday in almost two years, and I travel far less for work than I used to,” he said. “If I go to half the conferences I used to, that’s significant. And it raises questions universities should be asking themselves: Do we really need to fly as much as we do? Could we design better, more imaginative ways to meet?”

A challenge to the middle classes

Both authors say that while the private jets taken by the ultra-rich make headlines, the vast majority of environmental impact in wealthy countries like the UK comes from ordinary, affluent citizens — including the people most likely to read their book.

“We like to think of ourselves as regular, middle-class people,” said Davison. “But almost everyone in the professional classes belongs to the global rich. That comes with responsibility and with the power to act.”

This doesn’t mean giving up what makes life worth living, however. “The things we value most— reading, singing, dancing, being with friends and family — none of that is threatened by living more responsibly,” he said.

But it does mean making choices, and acknowledging the moral weight of those choices. Ancient traditions, from Plato to Aristotle to Christian ethics, Davison said, ask us to live in ways we can be proud of, whether or not others make the same sacrifices.

“Across ethical traditions, that kind of question always comes up,” he said. “Is good only worth doing if everyone else does it?”

“If everyone says they won’t act until someone richer does it first, then nothing is ever going to happen,” said Allwood. “It’s almost like refusing to help someone who is hurt until everyone else does.”

The new climate denialism

Both authors see a new, subtler form of climate denialism emerging — one that doesn’t necessarily dispute the science, but insists that nothing meaningful can be done without destroying the economy.

Davison disagrees with this pessimistic outlook. “There are lots of things we can do, and many of them save money,” he said. “Not everyone can afford to do everything — but the people who can afford it are usually the ones having the biggest impact, with the most capacity to change.”

Allwood says that this is a big, but different innovation opportunity, and has set up five spin-out companies that each demonstrate business growth compatible with reduced resource use. Many effective actions are within reach just by making different choices: retrofitting homes, reducing flights, supporting local change, and using influence in workplaces and professional networks. Small choices add up, especially when widely adopted.

“Change often starts when a small group decides to do something differently, whether that’s at the level of a household, a workplace or an institution,” said Allwood. “That’s where real momentum comes from.”

“Individual and workplace action can start to shift what we consider normal,” said Davison. “And that can start to shift political reality. We can reclaim hope, not just as blind optimism, but as a political virtue. None of us is helpless.”

Allwood and Davison say that our choices are not about punishment or guilt, but about honesty.

“We’re not saying life has to get worse,” said Allwood. “We’re saying it has to change.”

Julian Allwood is a Fellow of St Catharine’s College, Cambridge. Andrew Davison is an alumnus and former Dean of Chapel at Corpus Christi College, Cambridge, and is currently a Fellow of Christ Church College, Oxford.