Over at AEI's Enterprise Blog, Mark J. Perry has a weird post about how all the dire predictions that environmentalists were making back in the 1970s never panned out. "In fact," he writes, "according to new data available from the Environmental Protection Agency, air quality today in the U.S. is actually better than ever before." He even has a graph:

Okay, but why do we suppose pollution just magically dropped like that? Perry claims it's because the United States got richer. Here's another possibility: In 1970, Congress amended the Clean Air Act to tackle, among other pollutants, nitrogen dioxide, sulfur dioxide, carbon monoxide, and lead (the new rules were slowly phased in over the next decade). Most notably, the law acted to phase out lead from gasoline by the mid-1980s. And lo and behold, it worked—you can see a sharp drop in lead emissions over that period (with a few further steps needed after that). It was a massive public-health success story.

So the bleak predictions of 1970s-era environmentalists never panned out, but largely because they helped enact rules that prevented those outcomes. Similarly, all those old warnings about the ozone layer never came true because the world got together and banned CFCs. And, likewise, if greens today are successful in pushing the world to sharply reduce greenhouse-gas emissions, then all those apocalyptic forecasts about global warming probably won't come true, either. This isn't that complicated.

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