Ozone depletion
From Conservapedia
The ozone depletion theory states that emissions of freon from air conditioners and spray cans have (1) depleted the sky's ozone layer which (2) caused more harmful ultraviolet sunlight to reach the Earth's surface which in turn (3) increased the incidence of deadly human skin cancer.
This theory is well accepted within the scientific community. The 1995 Nobel Prize in Chemistry was awarded to Paul Cruzen, Mario Molina, and Sherwood Rowland for describing the process by which chlorofluorocarbons degrade stratospheric ozone into elemental oxygen.
