The document discusses carbon sequestration and trading as methods to reduce atmospheric carbon dioxide levels. It describes how carbon is naturally exchanged through biogeochemical cycles and explains that human emissions have increased CO2 beyond natural levels. It then outlines different carbon sequestration methods including terrestrial sequestration through plants and soils, geologic sequestration via underground storage, and ocean sequestration through direct injection or fertilization. Finally, it defines carbon trading as an emissions capping and trading system aimed at incentivizing reductions in greenhouse gases.