From Ecopedia

Overview

Carbon is the most abundantly occurring chemical element on the earth’s surface. Carbon’s presence in the universe is only next to hydrogen, helium and oxygen elements, which are the three most abundantly found chemical elements in the universe.

As carbon is found in all known forms of life, the element forms the chemical basis of all life on earth. ^[1]

Carbon is present in most organic matter including fossil fuels and the more complex RNA and DNA molecules. The element is widely stored in:

• organic molecular form, in both living and dead organisms
• as carbon dioxide gas in the atmosphere
• as organic matter in the soils
• as sedimentary rock deposits on earth
• as dissolved atmospheric CO2 in the oceans, and also
• as calcium carbonate shells in sea organisms^[2]

In nature, carbon occurs in free allotropic forms of diamond, graphite, fullerenes and white carbon. ^[3]

Carbon Cycle

Carbon cycle is a complex biogeochemical cycle, in which carbon is exchanged and recycled among the earth’s biosphere, pedosphere (outermost soil-containing layer), geosphere, hydrosphere as well as the atmosphere. ^[4]

The carbon cycle is, thus, a natural recycler of carbon atoms. When plants absorb the atmospheric carbon dioxide for photosynthesis, carbon atoms are utilized for making sugars, which are later released back into the atmosphere after passing through various forms.

Carbon dioxide is a major constituent of the carbon cycle and is emitted as a by-product during fossil fuel combustion, combustion of vegetable material or other inorganic processes.

Oceans as Carbon Sinks

Compared to the atmospheric presence, around fifty times additional carbon in the form of carbon dioxide, carbonic acid, bicarbonate as well as carbonate ions exists in ocean waters.

Environmental Impacts

Carbon dioxide - a Major Air Pollutant

Carbon dioxide is considered to be a major air pollutant, contributing significantly to the greenhouse effect and global warming phenomenon.

Acting as enormous carbon sinks, oceans take up around one third of carbon dioxide emitted during human activity. Since the solubility of CO2 decreases with increasing sea temperatures, excess heat in oceans leads to decreased solubility of the gas, resulting in ocean acidification.

Human activities are found to significantly increase carbon dioxide levels in the atmosphere leading to the greenhouse effect. As per the observations of Intergovernmental Panel on Climate Change (IPCC), most of the increase in global temperatures since mid-twentieth century could be attributed to extensive human activity, resulting in increased concentrations of GHGs like carbon dioxide and carbon monoxide. Environmentalists observed that CO2 contribution to the greenhouse effect is between 9-26%.

The Greenhouse effect is the major contributing factor for the Global warming phenomenon. If the current trend of increased GHG production continues, severe climate changes such as severe droughts, floods, rising sea levels, altered rainfall patterns are bound to occur. ^[5]

Deforestation

Deforestation is leading to loss of vegetation, which means most of the carbon dioxide present in the air is not being absorbed by the trees and plants for photosynthesis. As a result, a large amount of atmospheric carbon dioxide is getting accumulated in the atmosphere.

Carbon Sequestration

Carbon sequestration, a geo engineering technique, is being increasingly considered today for dealing with already-released carbon forms. The technique allows long-term storage of carbon forms including carbon dioxide, which aid in mitigating global warming.

Photosynthesis is a commonly occurring carbon sequestration in nature that allows plants and trees to soak up and store carbon, which would otherwise get released in the air and trap the atmosphere heat. ^[6]

Carbon Trading

Carbon trading is another attempt on the part of environment-conscious companies to claim reductions in carbon emissions by offering to pay for the required cuts by other companies. ^[7]

International Agreements

Many countries across the world started adopting stringent measures to lower the carbon impact on the earth’s atmosphere. Some of the major attempts include reduction in the atmospheric levels of CO2, carbon monoxide and methane and other gas emissions in order to combat global changes in climate.

Two major UN (United Nations) treaties, UN Framework Convention on Climate Change (UNFCCC) agreed in 1992 and Kyoto Protocol, signed in 1997 set to minimize carbon emissions. The Kyoto Protocol, in particular, committed the member countries to set binding targets for minimizing carbon emissions, especially carbon dioxide gas emissions by about 5% against the levels recorded in 1990.

The protocol set a time period of five years, from 2008 to 2012, to achieve the target level. The rules set for the implementation of the protocol, known as “Marrakesh Accords”, were finalized and adopted at COP7 in the year 2001, in Marrakesh. ^[8]

References

1. ↑ http://en.wikipedia.org/wiki/Carbon
2. ↑ http://www.physicalgeography.net/fundamentals/9r.html
3. ↑ http://periodic.lanl.gov/elements/6.html
4. ↑ http://en.wikipedia.org/wiki/Carbon_cycle
5. ↑ http://wiki.answers.com/Q/What_negative_effects_does_carbon_dioxide_have_on_the_environment
6. ↑ http://en.wikipedia.org/wiki/Carbon_sequestration
7. ↑ http://www.guardian.co.uk/environment/2009/may/21/carbon-emissions-questions
8. ↑ http://unfccc.int/kyoto_protocol/items/2830.php