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Page 833
Another possible way of dealing with the acid rain concern would
be to introduce sulfate in the form of ammonium sulfate or
bisulfate, each of which is a neutral salt. This would avoid the
acid question from the start. Both salts are used frequently as
fertilizers and in the dilutions to be seen here would have a mild
fertilizing effect locally. These salts can be made by reacting
ammonia with sulfuric acid. The price of ammonia is about $100/t,
so the cost of the CCN might double, and there would be an
additional cost for equipment to run the reaction at sea. These
additional costs might increase the total by as much as 50 percent
to $0.15/t of carbon mitigated per year or $0.04/t CO2.
Necessary Cloud Condensation Nuclei
Experiments
If global-scale CCN emissions were to be considered in a serious
way a number of fundamental studies would need to be performed.
Among these would be the following:
• Exploratory studies of the effectiveness of CCN for
enhancing stratocumulus cloud cover, with a full statistical
analysis of covariates, and so on.
• Determination of CCN properties: (1) lifetimes of CCN at
various altitudes; (2) effectiveness in cloud enhancement; and (3)
effect of their precipitation on oceans.
• Determination of the fraction of SO2 emissions converted to CCN and the
resulting particle size distribution.
• Extension of the idea of CCN enhancement from local and
regional to global dimensions: a careful study of the scale
dependence of the effectiveness of cloud enhancement processes and
the interaction of clouds with the radiation field.
• Full confirmatory analysis of the effectiveness of CCN on
fractional cloudiness with carefully selected test statistics. A
multiplicity of analysis would have to take into account all
variables such as the humidity profile, convective processes, and
CCN count, along with methods for the study of precipitation
processes.
Note
1. Throughout this report, tons (t) are metric; 1 Mt = 1 million
tons; and 1 Gt = 1 billion tons.
References
Albrecht, B. A. 1989. Aerosols, cloud microphysics, and
fractional cloudiness. Science 245:1227–1230.
Angell, J. K., J. Korshover, and G. F. Cotton. 1984. Variation
in United States
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