One Earth, One Future Our Changing Global Environment (1990) / Chapter Skim
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4. System Interactions: Atmosphere, Oceans, Land, and Humans
4. System Interactions: Atmosphere, Oceans, Land, and Humans
Pages 31-48
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From page 31... ...
It is beyond the human ken, however, to study the whole, multiclimensional system at once. As the following sections attest, the effort to understand the dynamics driving change in the global environment is clesigned along the academic lines that essentially define classical disciplines.
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From page 32... ...
ATMOSPHERE Many of the earth's inhabitants live far from the oceans; concerns about tropical forests may seem remote to farmers on the American Plains, or to women gathering firewood in the Himalayas. But the atmosphere touches each of us.
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From page 33... ...
Analysis of air bubbles trapped in glacial ice and contemporary measurements reveal that carbon dioxide concentrations have increased by nearly 25 percent since the eighteenth century, when industrialization began. The main cause is the combustion of fossil fuels, which produces compounds that also contribute to problems such as local air pollution and acid deposition.
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From page 35... ...
His records cover a relatively brief interval, but are treasured by scientists: They clearly show that carbon dioxide is increasing in the global atmosphere, anct they also show a striking sawtooth pattern that reflects the entire biosphere of the Northern Hemisphere "breathing in" as plants grow in the warm months and "exhaling" when they are dormant. From studies of glacial ice samples, scientists know that the level of carbon dioxide during ice ages was about 200 parts per million.
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From page 36... ...
These computer models use mathematical equations to express the basic physical principles that govern the global atmosphere and then use actual data to test whether the models adequately simulate reality. The general circulation models, as they now exist, simulate the physical climate and geographical features on a very coarse scale.
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From page 37... ...
While much is known about ocean circulation and its coupling to atmospheric currents and pressure, less is certain about its ability to store additional carbon or about how much heat it will store in response to rising surface temperatures. The ocean is an immense reservoir of heat, holding the heat it absorbs from solar radiation longer than the land does.
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From page 38... ...
The free-fall of organisms from the surface to the ocean floor and the subsequent release of carbon as deep ocean waters are slowly recycled up to the surface waters have a profound effect on the way carbon is apportioned throughout the earth system. The movement of carbon through the earth system would be quite different if noting lived in the ocean.
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From page 39... ...
in other words, the physics of the system that provides nutrients such as carbon, nitrogen, and other elements from the deep ocean to the surface and that moves surface waters from one location to another also influences the nature of the food web. In turn, the nature of the food web influences the partitioning of carbon dioxide.
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From page 40... ...
Terrestrial plants take up more than 100 billion metric tons of carbon each year and return approximately as much to the atmosphere as plants die and decay. This cyclical exchange involves 20 times the amount of carbon released through combustion of fossil fuels.
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From page 42... ...
Each harbors distinct plant and animal communities, and each uniquely contributes to the functioning of the earth system. Tropical rain forests, for example, with abundant moisture and high temperatures that facilitate exceedingly rapid plant growth and decomposition of dead plant material, cover about 7 percent of the earth's land area but contribute a much larger share of the worId's annual turnover of biomass.
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From page 43... ...
As a result, many ecosystems were composed of wholly different combinations of species than are found anywhere today. During the ice age, the major vegetation zones shifted thousands of kilometers from their current positions, and so the fraction of the earth's surface covered by specific types of vegetation also was altered substantially.
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From page 44... ...
in light of the massive transformation under way in the global environment, water is of special interest because it exerts a strong moderating influence on the global climate system. Oceans, ice and snow, and clouds determine the earth's ability to reflect incoming radiation back to space, thereby helping to regulate temperature.
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From page 45... ...
Ecologists Robert Peters, of the World Wildlife Fund, and Thomas Lovejoy, of the Smithsonian Institution, traced the record of human activity and its effect on terrestrial plant and animal life in several regions of the world. One of the areas they studiecl, the Mecliterranean, provides a telling example.
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From page 46... ...
Now we know that human activities have become so pervasive that the effects are no longer local but are regional and even global in scale. Forest clearing is eliminating habitats where millions of species reside, acid rain is affecting lakes and streams in North America and Europe, and pollutants are changing the makeup of the atmosphere in ways that can affect climate and the protective ozone layer.
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From page 47... ...
While studies in fielcls including economics, psychology, and communication provide an invaluable research foundation, they have, for the most part, focused on what determines and controls individual behavior. Roberta Balstad Miller, director of the Division of Social and Economic Science of the National Science Foundation, stresses that the study of human aspects of global change must consider not only individual behavior but also entire institutions national laws and regulations, profit margins, transportation patterns, agricultural markets, and tax structures that are significant for the environment.
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From page 48... ...
48 THE EARTH AS A SYSTEM capability to choose, people can perceive and assess possible future changes that they hope to encourage or avoid. According to Harvard University's William C
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