Creeping climatic upheaval and corrosive global inequality are like two threads pulling apart civilisation’s fabric. To survive and thrive we face an unprecedented challenge of rapid transition. But the way we live is locked in by a culture of consumerism. David Boyle of the New Weather Institute and Clare Brass, Head of the Royal College of Art Sustain Programme, talk about precedents and our potential for change with historian Molly Conisbee.