Soil carbon management and climate change

World soils, a large reservoir of reactive carbon, moderate the global carbon cycle, atmospheric chemistry, radioactive forcing and ecosystem services; as such, soil carbon sequestration is important in limiting global warming to 2 degrees C. Among uncertainties are emissions from soils and permafrost, the CO2 fertilization effect, silicate weathering, the fate of eroded carbon, the efficiency of natural sinks, the permanence of carbon sequestered in soil and measurements of changes in soil carbon over short periods. Adoption of proven technologies can sequester carbon at the rate of 500-1000 kg/ha/year in croplands, 50-500 kg/ha/year in grazing lands, 500-1000 kg/ha/year in forestlands and 5-10 kg/ha/year of pedogenic carbonates in arid lands. Soil carbon is stabilized though deep placement, interaction with clays and the formation of stable aggregates. Adoption of recommended practices can be promoted by payments for ecosystems services. Researchable priorities include understanding trends of principal drivers, quantifying feedbacks related to climate change and impacts on ecosystem services.