The Global Carbon Cycle
The carbon cycle is the biogeochemical cycle by which carbon is exchanged among the major reservoirs of the Earth: the atmosphere, oceans, land, and living things.
Major Carbon Reservoirs:
Atmosphere: Carbon exists mainly as carbon dioxide (CO₂).
Oceans: The largest active carbon reservoir, holding carbon as dissolved CO₂, bicarbonate, and carbonate ions.
Land: Carbon is stored in soils, permafrost, and in the biomass of living organisms (especially forests).
Fossil Fuels: A huge, but historically stable, reservoir of carbon stored underground as coal, oil, and natural gas.
Major Carbon Fluxes (Movements):
Photosynthesis: Plants and algae take CO₂ from the atmosphere and convert it into organic matter.
Respiration: Organisms (including plants) release CO₂ back into the atmosphere.
Decomposition: Decomposers release carbon from dead organic matter.
Ocean-Atmosphere Exchange: CO₂ dissolves into and is released from the ocean surface.
Fossil Fuel Combustion: The burning of fossil fuels releases vast quantities of stored carbon into the atmosphere as CO₂.
The Greenhouse Effect and Climate Change
The greenhouse effect is a natural process that warms the Earth's surface.
1.Solar radiation strikes the Earth.
2.The Earth's surface warms up and radiates heat back outwards as infrared radiation.
3.Greenhouse gases (GHGs) in the atmosphere, such as water vapor (H₂O), carbon dioxide (CO₂), and methane (CH₄), absorb this outgoing infrared radiation, trapping the heat and keeping the planet warm enough for life.
The Enhanced Greenhouse Effect:
Human activities, primarily the combustion of fossil fuels, have drastically increased the concentration of CO₂ in the atmosphere.
This has upset the natural balance of the carbon cycle, moving vast amounts of carbon from the long-term fossil fuel reservoir into the active atmospheric reservoir.
This increased concentration of GHGs traps more heat, leading to a rise in global average temperatures, a phenomenon known as global warming, which is the primary driver of modern climate change.