<Li> One of the strongest predictions of the greenhouse effect is that the stratosphere will cool . Although this cooling has been observed, it is not trivial to separate the effects of changes in the concentration of greenhouse gases and ozone depletion since both will lead to cooling . However, this can be done by numerical stratospheric modeling . Results from the National Oceanic and Atmospheric Administration's Geophysical Fluid Dynamics Laboratory show that above 20 km (12 mi), the greenhouse gases dominate the cooling . </Li> <Li> As noted under' Public Policy', ozone depleting chemicals are also often greenhouse gases . The increases in concentrations of these chemicals have produced 0.34 ± 0.03 W / m of radiative forcing, corresponding to about 14 percent of the total radiative forcing from increases in the concentrations of well - mixed greenhouse gases . </Li> <Li> The long term modeling of the process, its measurement, study, design of theories and testing take decades to document, gain wide acceptance, and ultimately become the dominant paradigm . Several theories about the destruction of ozone were hypothesized in the 1980s, published in the late 1990s, and are currently being investigated . Dr Drew Schindell, and Dr Paul Newman, NASA Goddard, proposed a theory in the late 1990s, using computational modeling methods to model ozone destruction, that accounted for 78 percent of the ozone destroyed . Further refinement of that model accounted for 89 percent of the ozone destroyed, but pushed back the estimated recovery of the ozone hole from 75 years to 150 years . (An important part of that model is the lack of stratospheric flight due to depletion of fossil fuels .) </Li> <P> Since CFC molecules are heavier than air (nitrogen or oxygen), it is commonly believed that the CFC molecules cannot reach the stratosphere in significant amount . However, atmospheric gases are not sorted by weight; the forces of wind can fully mix the gases in the atmosphere . Lighter CFCs are evenly distributed throughout the turbosphere and reach the upper atmosphere, although some of the heavier CFCs are not evenly distributed . </P>

What is the harm from the depletion of earth ozone layer