How does rising atmospheric CO2 affect marine organisms?

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Cloud Carbon Content
Loflund, M., Kasper-Giebl, A., Schuster, B., Giebl, H., Hitzenberger, R. and Puxbaum, H.  2002.  Formic, acetic, oxalic, malonic and succinic acid concentrations and their contribution to organic carbon in cloud water.  Atmospheric Environment 36: 1553-1558.

In our Editorial of 1 August 2001, we discussed mankind's impact on the cooling power of clouds within the framework of the observations of Charlson et al. (2001), who note that current IPCC estimates of the first indirect climatic effect of aerosols (see Twomey, 1977) "do not include the combined influences of some recently identified chemical factors, each of which leads to additional negative forcing (cooling) on top of that currently estimated."  Since these latter phenomena are driven by, among other things, water-soluble organic compounds, we felt it important to report on this study of several such species recently detected in cloud water samples.

What was done
The authors analyzed the carbon content, as well as the inorganic ion content, of cloud water at a continental background site about 70 km southwest of Vienna, Austria during two intensive field campaigns (11-26 April 1999 and 6-29 March 2000).

What was learned
The total carbon concentration in the cloud water was determined to be similar to the individual concentrations of the main inorganic compounds (nitrate and sulphate).  Black carbon comprised 22% of the total carbon.  Six carboxylic acids comprised an average of 11% of the remaining organic carbon: acetic, formic, oxalic, succinic, malonic and pyruvic.  It was also determined that black carbon can be used as a tracer for the six carboxylic acids, as the sum of the identified organic carbon rose in a linear fashion in response to increases in cloud water black carbon content.

What it means
These data identify some of the major forms of anthropogenic-produced organic carbon that can enhance the cooling power of clouds.  They also provide an indication of their abundances and indicate a more simple way (linear correlation with black carbon) by which their presence may be evaluated.

Charlson, R.J., Seinfeld, J.H., Nenes, A., Kulmala, M., Laaksonen, A. and Facchini M.C.  2001.  Reshaping the theory of cloud formation.  Science 292: 2025-2026.

Twomey, S.  1977.  The influence of pollution on the short-wave albedo of clouds.  Journal of the Atmospheric Sciences 34: 1149-1152.

Reviewed 24 July 2002