In July of this year, during record-smashing heat waves and forest fires, a group of scientists published “Trajectories of the Earth System in the Anthropocene,” exploring the risk that climate feedbacks could lead to runaway heating and a “Hothouse Earth.” Will Steffen, Johan Rockström, and Katherine Richardson — from the Universities of Stockholm, Australia, and Copenhagen, with colleagues from Stanford, Cambridge, Potsdam, The Netherlands, and elsewhere — published the paper in the US