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Rockaholic Adventures

Rockaholic Adventures is the place for conversation and discussion about outdoor excursions. You'll also read reviews written from the perspective of today's technologically-advanced outdoorsman - one with a background in engineering and geology. Here, you'll find everything from discussions about geology-related engineering disasters to insights about how advances in technology have transformed modern-day extreme sports.

Rockaholic Adventures also covers topics such as urban planning and other anthro-induced changes to the access and preservation of natural areas. The blog's owner, Shawn, holds an A.S. from Hudson Valley Community College (HVCC) with a concentration in science and engineering, and a B.S. from the State University of New York (SUNY) at Albany with a major in geology.

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4 comments

The Missing Carbon Problem (Part 2)

Posted February 10, 2009 5:00 AM by Shawn

Hypothetically, there is a terrestrial sink for carbon dioxide (CO2). The real issue lies deeper than understanding the processes of photosynthesis and respiration. The real unknown factor evolving around the terrestrial ecosystem is in the feedback mechanisms and not the sequestering of carbon by crop yield. So, rather than debate whether biofuels are displacing the carbon budget, I'd like to bring to light how changes to world climate can influence how carbon is stored in a terrestrial environment.

The negative feedbacks or possible sinks would be CO2 fertilization of soils and warming- enhanced mineralization of nitrogen. Both play large rolls in the carbon-to-nitrogen (C:N) ratio of soils, which is less than that observed in woody tissue and more than that observed in soil organic matter. Theoretically, the CO2 fertilization allows for an increase in the growth of woody tissue and the storage of carbon in biomass. Nitrogen mineralization has the same affect in that it also increases plant growth.

Other processes suggest that global warming is a positive feedback or a loss of terrestrial carbon storage. Respiration rates are positively correlated with global warming. So, warmer climates allow for biomasses to give more CO2 back into the atmosphere

The issue at hand is that these processes are very poorly understood, and concrete evidence for large-scale sources and sinks is not a direct measurement. Is a CO2-enhanced warming trend going to feedback positively or negatively with the terrestrial ecosystem?

After asking ourselves if un-accounted for feedback mechanisms are the reason we have an unbalanced model of the global carbon budget, we can then debate the carbon mass existing in the terrestrial environment. Do changes in land use outweigh the terrestrial sink? Do we respire, decay and burn more organic carbon than we store?

Editor's Note: This is Part 2 in a multi-part series. Part 1 is already on-line.

References:

1. Chester, Roy. Marine Geochemistry Second Edition. Malden, MA: Blackwell Science Ltd. 2000, 2003

2. Richard Houghton, Senior Scientist, Carbon Research. Understanding the Global Carbon Cycle. Woods Hole Research Center, http://www.whrc.org/carbon/

3. Hesshaimer, Vago, Heimann, Martin, Levin, Ingeborg. Radiocarbon evidence for a smaller oceanic carbon dioxide sink than previously believed. Nature (London). 370 (6486), p. 201-203, 1994.

4. Frankignoulle, Michel , Borges, Alberto V. European Continental shelf as a significant sink for atmospheric carbon dioxide. Global Biochemical Cycles. Pages 569-576, September 1, 2001

5. Houghton, R. A. , Davidson, E. A. , Woodwell, G.M. Missing sinks, feedbacks, and understanding the role of terrestrial ecosystems in the global carbon balance, Global Biochemical Cycles. Vol. 12, No. 1, Pages 25-34, March 1998

6. Tsunogia, Shizuo , Ono, Tsuneo , Watanabe, Shuichi. Increase in total carbonate in the western North Pacific water and a hypothesis on the missing sink of anthropogenic carbon, Journal of Oceanography, Vol. 49, Pages 305-315, 1993

7. Burdige, David J. , Alperin, Marc J., Homstead, Juliana, Martens, Christopher S., The role of benthic fluxes of dissolved organic carbon in oceanic and sedimentary carbon cycling. Geophysical Research Letters, Vol.19, Pages 1851-1854, 1992

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#1

Re: The Missing Carbon Problem (Part 2)

02/10/2009 8:57 AM

Hi Shawn - A warming planet causes the permafrost - I think part of what you are referring to as the "terrestrial environment" - covering large parts of Siberia, a massive land-mass, to release long-stored (1,000's or millions of years?) methane (CH4) to the atmosphere, adding to the CO2 already there, and accelerating the warming trend. I believe this methane accounts for more of the carbon in the "missing carbon problem" you're describing.

You say there's still uncertainty with climate models, but to clarify this, I'd be curious to know what statistical confidence levels the scientists taking part in the U.N.'s Intergovernmental Panel On Climate Change quote for their climate change computer models.

With all the global tax dollars being spent to tackle this problem, and the number of countries committed to this project - the countries that signed onto the Kyoto Protocol and likely the U.S. at some point soon - I'd think the U.N. models are pretty refined at this point, but I need to educate myself more on this to give you a good counterpoint. :)

- Larry

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#2
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Re: The Missing Carbon Problem (Part 2)

02/10/2009 9:27 AM

From my research I always accredited Woods Hole Institute of Oceanography as presenting the most believable and creditable models that account for the carbon cycle. They also present numerical data representing generalized fluxes of carbon with estimated error. These figures show with any confidence level there still exist some unknown carbon sink.

Permafrost coupled with increased respiration rates due to warming trends only increases the positive feedback to global warming and negates any suggested terrestrial sink. A debate by many is that the growth of woody tissues and other plant life with a high C:N ratio helps store this lost carbon. I tend to think the feedback mechinisms of permafrost and respiration are countered by increased growing seasons and storage of carbon in new growth. Still at best as I understand it, when you couple the change in land use due to deforestation that the terrestrial role in the carbon cycle is a wash.

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#3
In reply to #2

Re: The Missing Carbon Problem (Part 2)

02/10/2009 10:09 AM

Thanks Shawn - Woods Hole data looks like it comes from a credible source - maybe they work with the IPCC to develop climate models - will go deeper when I have more time. - Larry

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#4
In reply to #2

Re: The Missing Carbon Problem (Part 2)

02/24/2013 10:27 PM

Could be attributed to die-off of plankton in the oceans from pollution. Also, most single cell organisms in the ocean have an optimum temperature range so warming of the waters may be reducing their numbers in a negatively influential way

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