Even as late as the 70 s , people thought that the pollution was causing global cooling . There was certainly localized polution , local air quality , that people recognized , so they built taller smoke stacks , then acid rain came , so the scrubbed the sulfer out of the smoke . It turns out that the same sulfer that was causing the acid rain and poisoning the air and water was masking the warming effect of CO 2 by reflecting sunlight back into space . In short , the effects of pollution are complex and CO 2 is a more subtle threat than some others issues that have been corrected or mitigated . After we cure the CO 2 issues , there will be other issues that come to the forefront . CO 2 isn ' t the only problem , it just happens to be the most urgent .