Rise in atmospheric CO2 accelerates as economy grows, natural carbon sinks weaken

Human activities are releasing carbon dioxide faster than ever, while the natural processes that normally slow its build up in the atmosphere appear to be weakening. These conclusions are drawn in a new study in the early online edition of the Proceedings of the National Academy of Sciences, October 22-26. The report states that “together, these effects characterize a carbon cycle that is generating stronger-than-expected climate forcing sooner than expected.”

Between 2000 to 2006, human activities such as burning fossil fuels, manufacturing cement, and tropical deforestation contributed an average of 4.1 billion metric tons of carbon to the atmosphere each year, yielding an annual growth rate for atmospheric carbon dioxide of 1.93 parts per million (ppm).

“This is the highest since the beginning of continuous monitoring in 1959,” states the report. The growth rate of atmospheric carbon dioxide is significantly larger than those for the 1980s and 1990s, which were 1.58 and 1.49 ppm per year, respectively. The present atmospheric concentration of carbon dioxide is 381 ppm, the largest concentration in the last 650,000 years, and probably in the last 20 million years.

While the worldwide acceleration in carbon dioxide emissions had been previously noted, the current analysis provides insights into its causes. “The new twist here is the demonstration that weakening land and ocean sinks are contributing to the accelerating growth of atmospheric CO₂,” says co-author Chris Field, director of the Carnegie Institution’s Department of Global Ecology.

Changes in wind patterns over the Southern Ocean resulting from human-induced global warming have brought carbon-rich water toward the surface, reducing the ocean’s ability to absorb excess carbon dioxide from the atmosphere. On land, where plant growth is the major mechanism for drawing carbon dioxide out of the atmosphere, large droughts have reduced the uptake of carbon.

Emissions from the burning of fossil fuels constituted the largest source of anthropogenic carbon, releasing an average of 7.6 billion metric tons each year between 2000 and 2006, a significant jump from 6.5 billion tons in the 1990s. Emissions generated by land-use changes such as deforestation have remained constant, but shifted in geographic focus.

Source: Carnegie Institution

   

• NotParker - Oct 23, 2007
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  Facts:
  
  1) The Southern Hempisphere is cooling and has been for 5 years
  2) More sunshine is reaching the earth
  3) CO2 is released by oceans when they warm up
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• Elenneth - Oct 23, 2007
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  The capacity for a liquid to hold a dissolved gas (i.e. dissolved carbon dioxide in ocean water) decreases as the temperature of the liquid increases. For example, an opened can of soda at room temperature will loose its carbonation much faster than an opened can of soda in the refrigerator.
  
  Therefore, the warmer the temperature of the ocean, the less of an ability it has to hold carbon dioxide and the greater its rate of dissolved carbon dioxide release. In this case, carbon-rich water, as it moves from a lower depth (read: cooler temperature) to a shallower depth (read: warmer temperature), it would make sense that it would release stored carbon dioxide.
  
  I am not certain that I have heard of that statement that more sunshine is reaching the earth. From where do you draw this?
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• mikiwud - Oct 25, 2007
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  If there are less clouds more heat reaches the Earth thus warming the oceans.The heating could be caused by thermal action from the Earth's core.As the greenhouse effect signature predicted by the computer models is not visible in the recorded data,this is more likley than AGW.
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• Elenneth - Oct 25, 2007
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  Cloud coverage also serves as insulation to keep the heat in. That is why deserts, which are often devoid of cloud cover, can reach extreme daytime temperatures, while at night experience a drastic plummet in the temperature because of a lack of cloud cover to insulate against lost heat.
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• mikiwud - Oct 26, 2007
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  Elenneth,
  That is the local effect felt anywere it happens.
  Globaly the effect is more cloud,less heat reaches the earth also more is reflected back into space and vice versa.
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