describe atmospheric chemistry and its contribution for the current global climate change
Answers
Within the atmospheric chemistry component of the U.S. Global Change Research Program there is a well-defined science focus with a track record of dealing with public policy implications. Development and implementation of the Montreal Protocol rested on a solid scientific foundation, realized through a strong international network of scientists and, within the United States, a multiagency effort led by the National Aeronautics and Space Administration (NASA). In fact, the model of an international, integrated, and periodically repeated assessment was largely formed from the United Nations Environment program/World Meteorological Organization Ozone Assessments. Moreover, this research area has a rich history of interaction with the human dimension components at fine spatial scales, as a natural consequence of air pollution studies and policies. Current developments in atmospheric chemistry are revealing the close links between chemistry, radiation, dynamics, and climate. Examples include the powerful role played by aerosol formation in both the boundary layer and the upper troposphere, chemical initiation of subvisible cirrus in the region of the tropopause, the control exerted by water vapor and temperature on the sharply nonlinear partitioning of halogen and hydrogen radicals in the lower stratosphere, and the importance of stratosphere-troposphere exchange on the composition and meteorology of the upper troposphere and lower stratosphere.
However, there are significant lessons to be remembered—lessons resulting from significant research shortcomings. Failure to recognize the Antarctic ozone hole sooner demonstrates the consequences of overreliance on models and how the selected observational strategies are so critically tied to success. This lesson must not be forgotten in studying the complexities of climate, ecosystems, and the chemistry of the troposphere.
Today, we have far deeper knowledge about the chemistry of the atmosphere than we did just a decade ago. We also know more clearly what we do not know. These issues are also addressed in a recent National Research Council report (NRC, 1998) that is consistent with the perspective put forward in this chapter. Key challenges to atmospheric chemistry in the coming decade can be expressed in five Research Imperatives, where each Research Imperative combines one or more primary Scientific Questions with the need to know from a human dimensions perspective:
Stratospheric ozone and ultraviolet (UV) radiation. Define and predict secular trends in the intensity of UV exposure that the Earth receives. Document the concentrations and distributions of stratospheric ozone and the key chemical species that control its catalytic destruction and elucidate the coupling between chemistry, dynamics, and radiation in the stratosphere and upper troposphere.
Greenhouse gases. Determine the fluxes of greenhouse gases into and out of the Earth 's systems and the mechanisms responsible for the exchange and distribution between and within those systems. Expand global detection techniques to elucidate the processes that control the abundances and variability of atmospheric CO2, CH4, N2O, and upper-tropospheric/lower stratospheric O3 and water vapor.
Photochemical oxidants. Develop the observational and computational tools and strategies that policy makers need to effectively manage ozone pollution, and elucidate the processes that control and the relationships that exist among ozone precursor species, tropospheric ozone, and the oxidizing capacity of the atmosphere.
Atmospheric aerosols and UV/visible radiation. Document the chemical and physical properties of atmospheric aerosols, and elucidate the chemical and physical processes that determine the size, concentration, and chemical characteristics of atmospheric aerosols.
Toxics and nutrients. Document the rates of chemical exchange between the atmosphere and ecosystems of critical economic and environmental import, and elucidate the extent to which interactions between the atmosphere and biosphere are influenced by changing concentrations and depositions of harmful and beneficial compounds.