How does rising atmospheric CO2 affect marine organisms?

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CO2 Trumps Air Temperature,
Keeping Carbon in the Ground

Van Ginkel, J.H., Whitmore, A.P. and Gorissen, A.  1999.  Lolium perenne grasslands may function as a sink for atmospheric carbon dioxide.  Journal of Environmental Quality 28: 1580-1584.

What was done
Based on prior experimental work that established the growth and decomposition responses of perennial ryegrass (Lolium perenne L.) to atmospheric CO2 enrichment and increasing temperature, the authors developed a model to assess the validity of the oft-stated idea that CO2-induced global warming will be self-amplifying, as a consequence of a temperature-induced increase in plant residue decomposition that will release greater quantities of CO2 into the air and increase the rate of rise of atmospheric CO2, thus exacerbating the initial CO2-induced global warming.

What was learned
It was found that at both low and high soil nitrogen contents, CO2-induced increases in plant growth and CO2-induced decreases in plant decomposition rates "are more than sufficient to counteract the positive feedback caused by the increase in temperature."  Indeed, for realistic scenarios of CO2 and temperature increases, the authors calculate a carbon sequestration rate sufficient to remove 55% of the ongoing atmospheric CO2 increase above ryegrass grasslands.

What it means
This study is particularly important, as it refutes the popular idea that CO2-induced global warming will be self-amplifying because of a temperature-induced increase in plant decomposition rates that puts more CO2 into the air and thereby creates more warming.  Not only is this concept shown herein to be invalid - in that it does not include the positive effects of atmospheric CO2 enrichment - it is shown to be qualitatively wrong when all pertinent factors are considered.  The phenomenon in question actually acts to reduce whatever warming might be caused by rising atmospheric CO2 levels; and it works even better to reduce non-CO2-induced global warming, which is a natural "fix" we might really need if the warming of the past century or so is due to something other than the concomitant CO2 increase, as we tend to believe.

Reviewed 15 November 1999