Plans to end global warming hinge on driving net greenhouse gas emissions to zero (plus or minus a few gigatonnes). The old methods—growing more and bigger trees in temperate and tropical forests, stuffing more carbon into soils—can be cheap, but they have limits. What would it take to scale DAC to many billions of tonnes a year? That total will increase if global emissions do not start falling quickly. All novel methods, such as DAC, biochar, and enhanced rock weathering, remove less than 2 million tonnes a year, according to the 2024 State of Carbon Dioxide Removal study.