More nation states are now committing to zero net carbon by 2050 at the latest, which is encouraging, but none have faced up to the transformation of economies, societies and lives that this will entail. This article considers two scenarios for a fair transition to net zero, concentrating only on climate change, and discusses the implications for contemporary ‘welfare states’. The first is the Green New Deal framework coupled with a ‘social guarantee’. I argue that expanded public provision of essential goods and services would be a necessary component of this strategy. The second scenario goes further to counteract runaway private consumption by building a sufficiency economy with ceilings to income, wealth and consumption. This would require a further extension of state capacities and welfare state interventions. The article provides a framework for comparing and developing these two very different approaches.