In early assessments of global warming, most curves were smooth. Rising concentrations of greenhouse gases would raise temperatures. Then glaciologists started finding evidence of extraordinarily abrupt jumps in regional temperatures. Other evidence revealed past eras when seas rose precipitously. The possible shutdown of important Atlantic Ocean currents added to the sense of nonlinear and disruptive risk. A certain best seller propelled the phrase

…At the Headwaters Gathering, an environmental conference at Warren Wilson College in Asheville, N.C., Herman Daly, whose focus is