Here is a number worth sitting with: in high-emission countries, at least 87% of the population would need to change the way they live — meaningfully, measurably — just to make the 1.5°C climate target theoretically possible by 2030. That figure comes from Stephanie Cap, an industrial ecologist at Leiden University in the Netherlands, who has spent years building detailed models of what decarbonisation actually looks like from the inside of a household. Cap's research examined five European countries — Germany, Spain, Latvia, Hungary and Sweden — each chosen because they represent a different starting point.

Sweden already runs on substantial renewable energy. Latvia depends heavily on imports. Spain and Hungary sit somewhere in between. Using a database called EXIOBASE, Cap traced the carbon footprint of everyday purchases: a bag of vegetables, a train ticket, a new laptop.

For every euro spent, the model calculated the emissions hidden inside the supply chain. It is, frankly, a remarkable way to make the invisible visible. So what actually moves the needle? Three changes stood out above all others: ditching petrol and diesel cars, replacing fossil-fuel heating systems, and shifting toward plant-based diets.

These three shifts, her scenarios show, consistently delivered the largest emissions reductions across every country studied.