There were a small number of scientists who in the '70s were predicting cooling. Those scientists agreed that greenhouse gases cause warming, but they thought

There were a small number of scientists who in the '70s were predicting cooling. Those scientists agreed that greenhouse gases cause warming, but they thought that the cooling effect from particulate pollution would be more significant. The thing about particulates is that they and some of theor bad effects are very clearly directly noticeable to the average person. You could see them in the air, and feel and taste and smell then when you would breath that air. That makes it much more feasible politically to deal with them, and Congress and the states enacted many laws and programs to do so. And so particulate levels dropped dramatically over the next several years, invalidating the assumption of the models that predicted cooling.