Global Climate Change: Components and Consequences
Gist, Ginger L., Journal of Environmental Health
Since the December 1997 meeting of world leaders in Kyoto, Japan, the issue of global climate change has been the subject of "heated" discussions. In June NEHA's Council of Delegates adopted a position on global climate change (Journal of Environmental Health, November 1997). Given the current arguments and misconceptions surrounding this issue, I thought it would be useful to revisit the topic of global climate change.
Global warming and global climate change have become synonymous in the public's mind. As environmental health professionals, we know the difference is vast. Although temperature change is certainly a major component, many other factors contribute to the problem of climate change.
Climate change has three basic components. First, if the Earth's energy balance is altered, the climate of the Earth is also altered. In 1896, a Swedish scientist, Svante Arrhenius, was the first to note an increase in the amount of atmospheric carbon dioxide (C[O.sub.2]), primarily caused by increased industrial activity. Indeed, C[O.sub.2] has increased by 25 percent in the last 250 years, and C[O.sub.2] is predicted to double by the middle of the next century. Plants, which remove C[O.sub.2] from the atmosphere, have been unable to keep up with demand resulting from the higher C[O.sub.2] levels and increased deforestation. The increased C[O.sub.2] has acted as a blanket, keeping solar energy trapped below it. In addition, release of chlorofluorocarbons from aerosol cans, rockets, and supersonic aircraft has depleted the ozone layer; consequently more solar radiation reaches Earth. The planet no longer is capable of releasing energy at the same rate it absorbs it. The energy budget has become unbalanced.
The second component of climate change is the effect particulates have on the earth's precipitation patterns. Levels of particulate matter, such as smoke and dust, have greatly increased in our atmosphere; this matter is then available to form precipitation nuclei. Two excellent examples of altered precipitation are in the U.S. Midwest, where transpiration from corn crops has been found to fuel storm systems, and in Australia, where smoke particles from burning sugar cane stubble have formed such good precipitation nuclei, that areas downwind of the cane fields have experienced a 20 percent drop in precipitation.
The third component is the effect of heat produced by human activities. The best examples of this effect are thermal blankets created by urbanization. Also, acid rain forms when sulfur and nitrogen oxides, which are released into the atmosphere by the burning of fossil fuels, combine with water. Acid rain contributes to desertification, and, once again, increased temperatures result.
Many other events can contribute to climate change, such as small sustained changes in the water balance as a result of urbanization, erosion, and increased irrigation; radioactive contamination from testing and use of nuclear weapons; and water pollution at levels too high to permit renewal of purity. …