ve in areas where vast tropical forests have been burned away may account for some of the rise in the methane levels. But no one is certain what all the methane sources contributes to global warming, although its effect is probably much greater than once thought. In addition, there have always been warming and cooling trends and it is possible that the hot years of the 1980s could give way to a cooler cycle. Since the late 1800’s for example, there have been fluctuations in decade averages for temperature. Although temperatures rose steadily until the 1980s, they dropped slightly over the next two decades. Still it appears that unless changes are made to cut back the emission off greenhouse gases, they will continue to build up in troposphere. This in turn will indirectly affect the abundance of stratospheric ozone - by modifying the temperature structure of the atmosphere and hence the rates of ozone destruction. Warmer temperatures in the troposphere are predicted to lead to colder temperatures in the stratosphere, which would allow ice clouds to develop beyond the Polar Regions, providing the surface for additional ozone. Since increased ozone loss allows more UV radiation to reach the earth, not only warming trends would continue but also the effects of harmful radiation would be enhanced. Theory states that CFCs in aerosol spray cans could be destroying the ozone layer. The public reacted quickly, flooding congress with mail and telephone calls urging a ban on CFC aerosols. The federal government sponsored a study that confirmed the hazard posed by CFCs, which led to their eventual ban on aerosol spray cans. Now spray can contain other type of propellant, and to assure consumers that a touch if the spray value will not add to the CFC burden in the stratosphere, some of manufacturers even paste labels on the can. Because of the CFC aerosol ban, Americans generally were convinced that the ozone layer had been adequately protec...
