Saturday, May 10, 2008

Ozone depletion and global warming

Although they are often interlinked in the mass media, the connection between global warming and ozone depletion is not strong. There are four areas of linkage:
The same CO2 radiative forcing that produces near-surface global warming is expected to cool the stratosphere.[citation needed] This cooling, in turn, is expected to produce a relative increase in ozone (O3) depletion and the frequency of ozone holes.

Radiative forcing from various greenhouse gases and other sources
Conversely, ozone depletion represents a radiative forcing of the climate system. There are two opposing effects: Reduced ozone causes the stratosphere to absorb less solar radiation, thus cooling the stratosphere while warming the troposphere; the resulting colder stratosphere emits less long-wave radiation downward, thus cooling the troposphere. Overall, the cooling dominates; the IPCC concludes that "observed stratospheric O3 losses over the past two decades have caused a negative forcing of the surface-troposphere system"of about −0.15 ± 0.10 watts per square meter (W/m²).
One of the strongest predictions of the greenhouse effect theory is that the stratosphere will cool.[citation needed] 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 (12.4 miles), the greenhouse gases dominate the cooling.
Ozone depleting chemicals are also greenhouse gases. The increases in concentrations of these chemicals have produced 0.34 ± 0.03 W/m² of radiative forcing, corresponding to about 14% of the total radiative forcing from increases in the concentrations of well-mixed greenhouse gases.
The long term modeling of the process, its measurement, study, design of theories and testing take decades to both document, gain wide acceptance, and ultimatly become the dominant paradigm. Several theories about the descruction of ozone, were hyphtosized in the 1980s, published in the late 1990s, and are currently being proven. Dr Drew Schindell, and Dr Paul Newman, NASA Goddard, proposed a theory in the late 1990s, using a SGI Origin 2000 supercomputer, that modeled ozone destruction, accounted for 78% of the ozone destroyed. Further refinement of that model, accounted for 89% of the ozone destoryed, 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 staratospheric flight due to depletion of fossil fuels.

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