"Huge quantities of carbon are actively exchanged between the atmosphere and other storage pools, including the oceans, vegetation, and soils on the land surface. The exchange, or flux, of carbon among the atmosphere, oceans, and land surface is called the global carbon cycle. Comparatively, human activities contribute a relatively small amount of carbon, primarily as carbon dioxide (CO2), to the global carbon cycle. Despite the addition of a relatively small amount of carbon to the atmosphere, compared to natural fluxes from the oceans and land surface, the human perturbation to the carbon cycle is increasingly recognized as a main factor driving climate change over the past 50 years. […] Congress is considering legislative strategies to reduce U.S. emissions of CO2 and/or increase the uptake of CO2 from the atmosphere. Congress may also opt to consider how land management practices, such as afforestation, conservation tillage, and other techniques, might increase the net flux of carbon from the atmosphere to the land surface. How the ocean sink could be managed to store more carbon is unclear. Iron fertilization and deep ocean injection of CO2 are in an experimental stage, and their promise for long-term enhancement of carbon uptake by the oceans is not well understood. Congress may consider incorporating what is known about the carbon cycle into its legislative strategies, and may also evaluate whether the global carbon cycle is sufficiently well understood so that the consequences of longterm policies aimed at mitigating global climate change are fully appreciated."
CRS Report for Congress, RL34059