oil, coal and natural gas GHG emissions at least 80% by 2050 GHG emissions at least 80% by 2050 Scientific American]. This one trillion metric tons of carbon um trilhão de toneladas métricas mundiais de carbono only add roughly 1 trillion metric tons of carbon Scientific American]. only add roughly 1 trillion metric tons of carbon Scientific American]. one trillion metric tons of carbon 80 percent drop by 2050