![the carbon cycle the carbon cycle](https://gedi.umd.edu/wp-content/uploads/2018/04/s07_CarbonCycle-1024x961.png)
Incorporating both natural processes and human-induced activities, the flux from atmosphere to biosphere is estimated at 1.4 GtCyr −1, representing the annual net accumulation of carbon in the biosphere. The terrestrial biosphere is a slightly smaller net sink. The largest natural flux is experienced between the atmosphere and the ocean where the ocean acts as a net sink of 1.7 GtCyr −1. During the 1990s, this source was reportedly 6.3 GtCyr −1 and is considered the main cause of large increases in atmospheric CO 2 concentrations over the past 100 to 150 years. The largest anthropogenic flux within the global carbon cycle is caused by the anthropogenic burning of fossil fuels. Anthropogenic processes such as burning fossil fuels for energy, as well as deforestation contribute a significant net positive flux to the atmosphere. Natural carbon fluxes are driven primarily by plant photosynthesis, respiration, and decay as well as oceanic absorption and release of CO 2. The overall net flux of the global carbon cycle indicates that carbon is accumulating in the atmosphere at an average rate of 3.2 GtCyr −1. Various natural and anthropogenic processes stimulate CO 2 fluxes between the reservoirs. The carbon stored in soil (which includes detritus, soil organic matter, and inert carbon) are 1400 GtC with plants accounting for a further 550 GtC. Due to their heterogeneity, biomass carbon stocks are difficult to measure empirically. Atmospheric carbon accounts for a further 750 GtC.
![the carbon cycle the carbon cycle](https://i2.wp.com/www.alevelgeography.com/wp-content/uploads/2018/04/Carbon-Cycle.gif)
The majority is stored in glacial deposits and minerals, fossil fuels, and the deep oceans. The total carbon stored in the earth's surface is estimated at more than 650,000,000 GtC. The net result of these processes is an increase in atmospheric CO 2 concentration of +3.2 GtCyr −1. Fossil fuel burning (−6.3 GtCyr −1) represents the largest anthropogenic release of CO 2 to the atmosphere. The most important natural fluxes in terms of the atmospheric CO 2 balance are the land-atmosphere exchange (+1.4 GtCyr −1), which includes land-use change and in enhanced vegetation growth, and the physical ocean-atmosphere exchange (+1.7 GtCyr −1). A simplified summary of the global carbon budget is also given. The broken lines represent long-term (millennia) movement of carbon within the system. The simplified global carbon cycle carbon reservoirs (GtC) represented within the boxes and associated fluxes (GtCyr −1) indicated by solid arrows between the reservoirs.