" But one of the reasons everyone had converged on a cap-and-trade proposal was that it had already been successfully tried—and by a Republican president, no less. Back in 1990, George H. W. Bush’s administration had put a cap-and-trade system in place to curb the sulfur dioxide coming out of factory smokestacks and contributing to acid rain, which was destroying lakes and forests across the East Coast. Despite dire predictions that the measure would lead to factory closures and mass layoffs, the offending companies had quickly figured out cost-efficient ways to retrofit their factories, and within a few years, the problem of acid rain had all but disappeared. "

― Barack Obama , A Promised Land