Earth’s “average temperature could drop by six degrees.” Rasool added that “such a temperature increase could be sufficient to trigger an ice age!”
Basically, pollutants from burning coal and other fuels tend to reflect solar energy back into space. Scientists were worried that such man-made aerosols would block out so much sunlight that global temperatures would drop — just like how volcanoes can cause some atmospheric cooling.
Worry among the scientific community was apparently so strong that Gordon MacDonald, President Nixon’s science advisor, said that fossil fuel-driven cooling was “one of the serious problems” facing the world.
The Max Planck study suggests “that aerosol radiative forcing is less negative and more certain than is commonly believed.” In layman’s terms, aerosols are offsetting less global warming than was previously thought. And if aerosols aren’t causing as much cooling, it must mean carbon dioxide must be causing less warming than climate models predict.