Scientific American: Global warming is "unequivocal." Sea levels are creeping up at the fastest rate in 2,000 years. Concentrations of CO2 in the atmosphere have reached "levels unprecedented in at least the last 800,000 years" (or before modern humans evolved). Most importantly "human influence on the climate system is clear" and "continued emissions of greenhouse gases will cause further warming." Those are some of the key messages in the "Summary for Policymakers" of the physical science of global warming from the...