Thresholds of significant harm at global level: The journey of the Earth Commission

The planetary boundary framework proposes ‘safe’ boundaries, but these boundaries are not necessarily ‘just’. Hence, we ask: How has the Earth Commission defined just boundaries building on the concept of minimizing significant harm and how many people are currently exposed to harm above the safe and just threshold? We document the work of the Earth Commission to address these questions using our Earth System Justice framework. We conclude that: (a) from a justice perspective, nine criteria need to be considered when defining just boundaries; (b) the proportions of populations exposed to harm from exceeding safe and just boundaries today range from 11 to 84 % for the five domains studied (climate, biosphere, water, nutrients, aerosols); and (c) argue that the absolute upper limit for significant harm is possibly harm to 1 % of the population, which although not stringent enough to leave no one behind, would require radical transformations, given the populations currently already above the threshold.