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Environmental Science: A Global Concern 5/e Cunningham/Saigo | |||||
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Environmental Science: A Global Concern 5/e Cunningham/Saigo | |||||
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Chapter Summary |
Chapter 17: Air, Climate, and Weather |
The atmosphere and living organisms have evolved together so that the present chemical composition of the air is both suitable for, and largely the result of, biological processes. Compression concentrates most gas molecules in a thin layer (the
troposphere) near the earth's surface. Upper layers of the atmosphere, while too dilute for life, play an important role in protecting the earth's surface by intercepting dangerous ultraviolet radiation from the sun. The atmosphere is relatively transparent to visible light that warms the earth's surface and is captured by photosynthetic organisms and stored as potential energy in organic chemicals.Heat is lost from the earth's surface as infrared radiation, but fortunately for us, carbon dioxide and water vapor naturally present in the air capture the radiation and keep the atmosphere warmer than it would otherwise be. When air is warmed by conduction or radiation of heat from the earth's surface, it expands and rises, creating convection currents. These vertical updrafts carry water vapor aloft and initiate circulation patterns that redistribute energy and water from areas of surplus to areas of deficit. Pressure gradients created by this circulation drive great air masses around the globe and generate winds that determine both immediate
weather and long-term climate.Earth's rotation causes wind deflection called the
Coriolis effect, which makes air masses circulate in spiraling patterns. Strong cyclonic convection currents fueled by temperature and pressure gradients and latent energy in water vapor can create devastating storms. Another source of storms are the seasonal winds, or monsoons, generated by temperature differences between the ocean and a landmass. Monsoons often bring torrential rains and disastrous floods, but they also bring needed moisture to farmlands that feed a majority of the world's population. When the rains fail, as they do in drought cycles, ecosystem disruption and human suffering can be severe.Many procedures claiming to control the weather are ineffectual, but some human actions-both deliberate and inadvertent-may change local weather and long-term climate. Cloud seeding can induce rain or disperse fog under the right atmospheric conditions. Improving the local situation, however, often makes things worse somewhere else. It is not yet clear what the future of our weather and climate will be. Many scientists warn that the gaseous pollutants we release into the atmosphere may trap radiant energy and cause a global warming trend that could drastically disrupt human activities and natural ecosystems. Understanding and protecting this complex, vital aspect of our world is clearly essential.
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