Which of the following is not true with regard to sulfate aerosols?

A. Sulfate aerosols come from both natural and anthropogenic sources.
B. Deliberately increasing sulfate aerosol concentrations in the stratosphere has been proposed as a method of countering an enhanced greenhouse effect.
C. Sulfate aerosols have a relatively short residence time in the atmosphere.
D. Warming caused by sulfate aerosols is likely to have been playing a role in the enhanced greenhouse effect.
E. Sulfate aerosols can serve as cloud condensation nuclei, increasing the albedo of clouds.