BOX 4-1 Global Climate Change: A Large-Scale, Complex Problem Requires an Interdisciplinary, Multi-Agency Approach

Atmospheric scientists have recently concluded that changes in atmospheric composition, driven by agricultural and industrial emissions of ''greenhouse gases," (primarily carbon dioxide and methane) are almost certainly causing a measurable warming of the earth's surface and lower atmosphere (IPCC, 1996). Furthermore, these scientists have concluded that scattering of incident sunlight by atmospheric aerosols, due to industrial emissions and biomass burning, has counteracted some of the potential warming. Current programs (driven by acid deposition and human health concerns) aimed at reducing atmospheric aerosol levels could therefore result in global warming beyond that already observed (IPCC, 1996).

As the climate warms, it may affect ecosystem viability, managed crop and forest yields, and human health. Changes could be induced both by shifts in mean temperatures and by the increases in extreme weather conditions (drought, flood, severe storms) that climate models predict will occur for many regions. Current models have demonstrated the key role that the hydrologic system plays in climate change and the dramatic impact that significant climate change may have on regional freshwater availability and quality. Exploratory studies have also suggested strong feedbacks between climate change and the ecology of many ecosystems (IPCC, 1996).

While it is clear that global warming is occurring, the degree to which it will continue to occur, what actions are stimulating it, and what actions will ameliorate unfavorable change are all still uncertain. Scientists are also very unsure about the future ramifications of global warming. Possible scenarios include rising sea levels from melting polar ice caps leading to coastal flooding, changes in precipitation patterns leading to drought in some regions, and the loss of plant and/or animal species unable to migrate fast enough to follow shifting climate conditions into regions where the species would remain acclimated. Suggestions that climate change may also have a significant impact on the rate and mechanisms of disease spread also need to be investigated (IPCC, 1996).

The processes that need to be investigated to adequately characterize global warming are far beyond the capabilities of EPA or any single agency. Rather, addressing the range of environmental problems related to global climate change will require an integrated, multi-agency effort. So far, the rate of global warming and global warming's impact on meteorological and hydrological systems as well as on terrestrial vegetation

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