Average global temperatures have not risen since 1998 even though emissions of carbon dioxide and other greenhouse gases continue to rise rapidly. Climate models predict temperatures should be increasing. This divergence for 16 years between increasing greenhouse-gas concentrations and constant temperature implies that we may not understand the true cause of climate change.
The world did warm approximately one degree Fahrenheit from 1970 to 1998 at the same time that ozone in the lower stratosphere became depleted, forming the Antarctic Ozone Hole. Ozone normally absorbs high energy ultraviolet solar radiation – radiation that is at least 48 times more energetic than infrared energy absorbed by greenhouse gases. When ozone is depleted, more of this energy reaches Earth, cooling the lower stratosphere and warming Earth.
In 1976, scientists found that human-manufactured chlorofluorocarbon gases (CFCs) deplete ozone in the lower stratosphere. When the Antarctic Ozone Hole was discovered in 1986, international concern led to negotiation of the Montreal Protocol, limiting manufacture of CFCs. The Montreal Protocol took effect in January, 1989. The rapid increase of CFCs in the atmosphere stopped by 1993. The rapid increase in ozone depletion stopped by 1995. The rapid increase in temperature stopped by 1998.
Dr. Peter L. Ward, a geophysicist with the U. S. Geological Survey in Menlo Park, California for 27 years, will report on these and related findings at the Annual Meeting of the American Geophysical Union in San Francisco this Thursday. After retiring from the USGS, Ward has been able to devote his fulltime effort for more than eight years of trying to understand the geophysics of climate change. “Ozone depletion”, he says, “is caused by CFCs and also by volcanic eruptions. While explosive eruptions cool Earth, effusive basaltic eruptions – typical in Hawaii and Iceland – warm Earth. The interplay between these two types of volcanism appears to explain climate change throughout geologic time.”
“The Ozone-depletion theory of global climate change” Ward concludes, “explains the onset of global warming around 1970, the demise of global warming in 1998, and the changes in global warming throughout Earth’s history much more directly and in much more detail than greenhouse-gas theory.”
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