A wise move
"Water vapor is a naturally occurring greenhouse gas and accounts for the largest percentage of the greenhouse effect. Water vapor concentrations fluctuate regionally, but human activity does not directly affect water vapor concentrations except at very local scales.
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Intergovernmental Panel on Climate Change (IPCC) IPCC Third Assessment Report chapter lead author Michael Mann considers citing "the role of water vapor as a greenhouse gas" to be "extremely misleading" as water vapor can not be controlled by humans"
http://en.wikipedia.org/wiki/Greenhouse_gas
