Climate change or acid rain?

Ken Caldeira suggests slowing warming with sulfate particles. Greg Mankiw worries about unintended consequences. I may be misremembering, but . . . weren't sulfates the things from coal plants that caused acid rain?

This article available online at:

http://www.theatlantic.com/business/archive/2007/10/climate-change-or-acid-rain/2154/