The Carbon Cycle and Atmospheric Carbon Dioxide Sources

The principal source of carbon dioxide is degassing of the Earth from volcanic activities, mid-ocean ridges, hotspots or subduction-related volcanism. Carbon is converted into different forms through the atmosphere, hydrosphere, and lithosphere. Part of the outgassed carbon dioxide remains in the atmosphere, some of them is dissolved in the oceans, some carbon is preserved as biomass in living or dead organisms, and some is deposited as carbonate rocks such as limestone. 
 

Here, is a table shows Carbon pools in the major reservoirs on earth from Wikipedia:

Pool	Quantity (gigatons)
Atmosphere	720
Oceans (total)	38,400
Total inorganic	37,400
Total organic	1,000
Surface layer	670
Deep layer	36,730
Lithosphere
Sedimentary carbonates	> 60,000,000
Kerogens	15,000,000
Terrestrial biosphere (total)	2,000
Living biomass	600 - 1,000
Dead biomass	1,200
Aquatic biosphere	1 - 2
Fossil fuels (total)	4,130
Coal	3,510
Oil	230
Gas	140
Other (peat)	250

Approximately eighty per cent of atmospheric carbon dioxide is from the Earth’s outgassing(Hibbard. 2000). Meanwhile, respiration and fuel combustion are other two major source of atmospheric carbon dioxide.

Respiration consumes oxygen from the atmosphere and produces carbon dioxide.

Oxygen + carbohydrate > energy + water + carbohydrate

O₂ + CH₂O > energy + H₂O + CO₂

On the other hand, photosynthesis takes carbon dioxide from the atmosphere and produce oxygen.

6CO₂ + 6H₂O (+ light energy) > C₆H₁₂O₆ + 6O₂

The combustion of organic matters will release carbon dioxide to the atmosphere.

C + O₂  > CO₂

Moreover, some of carbon dioxide is produced and released into the atmosphere via metamorphism of limestone （CaCO₃ + SiO₂ > CO₂ + CaSiO₃） and the precipitation of Calcium carbonate from calcium and bicarbonate in the ocean by maritime organisms such as corals.（Ca²⁺ + 2HCO₃^- > CaCO₃ + CO₂ + H₂O）  

Here is a short vedio from NASA briefly describes the carbon cycle of the Earth and the change of atmospheric carbon dioxide. 

From next post, I am going to talk about the impacts of change in atmospheric carbon dioxide, then I will    discuss about the potential methodologies of carbon reduction.

Reference: 

• Carbon pools in the major reservoirs on earth. http://en.wikipedia.org/wiki/Carbon_cycle#cite_note-GlobalCarbonCycle-1
• Falkowski, P.; Scholes, R. J.; Boyle, E.; Canadell, J.; Canfield, D.; Elser, J.; Gruber, N.; Hibbard, K. et al. (2000). "The Global Carbon Cycle: A Test of Our Knowledge of Earth as a System". Science 290 (5490): 291–296.
• The Carbon Cycle and Earth's Climate. http://www.columbia.edu/~vjd1/carbon.htm 
• Chemical precipitation: terrestrial carbon cycle. Encyclopædia Britannica, Inc.

Change of Carbon Dioxide and Temperature in History

The amount of Carbon dioxide changed through the history.  The value of atmospheric carbon dioxide had fluctuated from near 190 ppm to 280 ppm from 400,000 years ago till Pre - industrial time. It was around 180 during ice ages, and the number had reached to 325 ppm by the year 1970. After that, the concentration of atmospheric carbon dioxide increased dramatically to 380 ppm at the beginning of this century. In September of 2012, Mauna Loa dataset shows that the value was 391.07 ppm. It is predicted that the concentration might continue to grow till 400 ppm by the year 2015. On the other hand, the average temperature of the earth changed almost followed the change of atmospheric carbon dioxide concentration.  Especially the recent one hundred years, the global mean temperature and the concentration of carbon dioxide both increased considerably after the industrial revolution. 

IPCC (2007) described that "for the global average, warming in the last century has occurred in two phases, from the 1910s to the 1940s (0.35°C), and more strongly from the 1970s to the present (0.55°C). An increasing rate of warming has taken place over the last 25 years, and 11 of the 12 warmest years on record have occurred in the past 12 years."

As the Global mean temperature figure shows, the global surface temperatures had risen by approximately 0.74°C during the last 100 years from 1906 and 2005. Meanwhile, the concentration of carbon dioxide had increased by about 100 ppm over last hundred years.



Reference:

• IPCC, 2007: Observations: Surface and Atmospheric Climate Change. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change

Introduction of this blog

Welcome to my blog, this blog is a part of the course GEOG3057 Global Environmental Change. In the next several months, I will use this blog to write about this course and issues related to the global environmental change. 

My topic of this blog is "Carbon reduction". As the modern society develops constantly, the consumption of energy raises significantly, especially the combustion of fossil fuels (coal, oil and natural gas). Consequently, the proportion of carbon dioxide and also other greenhouse gases in the atmosphere increased considerably. 

As the Keeling curve shows, the percentage of carbon dioxide in the atmosphere had grown from around 315ppm to over 380ppm from 1960 to the year of 2010. Moreover, Mauna Loa dataset indicates that the value has reached to 391.07ppm in September 2012. 

Since carbon dioxide is the major greenhouse gas and causes global warming and global climate change, a concept is proposed by scientists – “Carbon reduction”. Carbon reduction is also called carbon offset. The University of Oxford Environmental Change Institute describes carbon offset is "a widely discussed mechanism whereby individuals and corporations pay for reductions elsewhere in order to offset their own emissions"(Lovell. 2007). 

In this blog, I will illustrate the origin of atmospheric carbon dioxide; natural storage of carbon dioxide; the development of atmospheric carbon dioxide in the past; the impacts of the change of atmospheric carbon dioxide on the environment and climate, meanwhile, I will discuss the potential approaches that may reduce atmospheric carbon dioxide and their pros and cons.

For the next post, I am going to talk about the change of atmopsheric carbon dixoide in histroy and its major sources. Here is a preview animation illustrates the history of atmospheric carbon dioxide.

Reference:

• Mauna Loa dataset. http://co2now.org/
• Lovell, H., Buckley, H. and Liverman, D., 2007. Carbon offsetting: sustaining consumption?