The Carbon Cycle

| 11/10/2010 7:53:27 AM

Photo by Pixabay/Foundry

As we discussed in my first posting, carbon dioxide helps stabilize the planet’s temperature, but increasing the atmospheric concentration of carbon dioxide will increase the global temperature.  Over millions of years Earth has been able to regulate the level of atmospheric carbon dioxide through the carbon cycle.  The burning of fossil fuels, such as coal and oil, in our factories, power plants and cars has disrupted this balance so that higher levels of carbon dioxide accumulate in the atmosphere. To appreciate the impact our burning of fossil fuels is placing on the planet we need to understand how the Earth recycles carbon dioxide through the carbon cycle.

The carbon cycle refers to the flow of carbon between the atmosphere, rocks, oceans and biosphere (all of Earth’s life forms).  Each of these is part of a reservoir which contains all the carbon on the planet. The carbon cycle is composed of two reservoirs: a long-term and a short-term.  By circulating carbon through these interconnected reservoirs the planet regulates the level of atmospheric carbon dioxide.

The long-term reservoir contains about 99.9 percent of the total carbon which is found mainly in rocks and fossil fuels and takes up to millions of years to recycle carbon dioxide.  In the long-term reservoir atmospheric carbon dioxide reacts with water and minerals in rocks to form calcium bicarbonate which enters rivers and ends up in the ocean where it becomes shells of various marine organisms.  When these organisms die the shells accumulate on the ocean floor and are eventually transformed into rocks and petroleum.  Over millions of years this transformed material is buried at depths of thousands of feet and the heat and pressure melts the rocks and converts the carbonate back to carbon dioxide.  Some of these rocks become part of volcanoes and the carbonate is released as carbon dioxide via volcanic eruptions. 

Carbon dioxide is also removed from the atmosphere by plants and the burial of dead plant matter.  In swamps this material is transformed into coal and in river deltas the material is converted into carbonaceous shale.

In the short-term reservoir, carbon is stored in the atmosphere, oceans and biosphere with the ocean containing the largest amount of carbon.  It takes months to centuries to recycle carbon dioxide through the short-term reservoir.  The ocean is the primary regulator of atmospheric carbon dioxide in the short-term reservoir because atmospheric and ocean carbon dioxide are in chemical equilibrium.  If there is an increase in atmospheric carbon dioxide there is a corresponding increase in oceanic carbon dioxide and vice versa.  There are two main ways in the short-term reservoir that carbon dioxide is removed from the atmosphere and enters the ocean.

Richard Hilderman, Ph.D.
11/11/2010 9:42:08 AM

t. brandt In reference to your comment "the warming from about 1880 to 1925 was faster than the warming from 1980 to 2010"--all the scientific evidence I have reviewed does not agree with this statement. Please send me references pertaining to your statement. Yes, there have been times in ancient past where the temperature has been extremely highly and the planet and life surived. However, there were massive species extinction. In our current global warming if we reach a "tipping point" the fate of the human species is not known. At the very least there will be a whole lot less of us on the planet.

t brandt
11/10/2010 9:05:20 PM

Actually, the warming from about 1880 to 1925 was faster than the warming from 1980 to 2010. And when we consider that about 2000 Siberian reporting stations were closed after the fall of the USSR in 1989 and the recent exposure of the fraud involved in the major organisations responsible for providing temp data, it isn't really all that obvious that there has been any warming during the past 30 yrs. Atm [co2] was 10-20x higher during the Carboniferous Age than it is now, yet world temps (if proxy data are to be believed) were still no warmer than 22degC. That's about 7deg warmer than now, yet the planet didn't die. In fact, it flourished. Why no "tipping point" then?

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