Climate scientists have discovered that particulate pollution in the late 20th century created a “warming hole” over the eastern United States — that is, a cold patch where the effects of global warming were temporarily obscured. The findings have implications for industrial nations (like China) that have not yet tightened air quality regulations.

Levels of copper, cadmium, lead and other metals in Southern California’s coastal waters have plummeted over the past four decades, which researchers attribute to sewage treatment regulations that were part of the Clean Water Act of 1972 and to the phase-out of leaded gasoline in the 1970s and 1980s.