Why a Planetary Boundary, If It Is Not Planetary, and the Boundary Is Undefined? A Reply to Rockström et al.

Nothing validates our concerns about Rockström et al.’s work more than their response to our critique of it. First, they state ‘a planetary boundary … is not equivalent to a global threshold or tipping point’. While we appreciate this statement, we struggle with understanding their distinctions between tipping points, planetary boundaries, safe operating space, resilience, and irreversible changes, terms we show permeate their work from its...