Serving Science and Society Into the New Millenium (1998) / Chapter Skim
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Part III Protecting the Environment
Part III Protecting the Environment
Pages 83-103
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Part III Protecting the Environment
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From page 85... ...
We have seen many examples of that shift. The BER program has done much important work and made major contributions to the understanding of many environmental problems the invention of radioecology by Eugene Odum at the Savannah River Laboratory in the early 1960s, the first attempts to develop climate models by Chuck Leith at the Lawrence Livermore National Laboratory, the seminal work that Warren Washington did at the National Center for Atmospheric Research, the studies of the fallout of radioactivity from various weapons tests, the theoretical and practical studies dealing with turbulent diffusion and transport by Frank Gifford at the Oak Ridge Atmospheric Turbulence and Diffusion Laboratory, the studies of long-range transport of plumes from power plants and the early work dealing with the acid-precipitation problem, and the launching of the first federal research program 20 yr ago to look at the greenhouse effect, which at the time was known only to very few scientists and science managers.
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From page 86... ...
The continuity and quality of the modern data for Mauna Loa, Hawaii, and the South Pole, displayed as weekly averages of daily measurements in figures 1 and 2, are tribute to the ingenuity and skill of C.D. Keeling at the Scripps Institute for Oceanography, who, long before it was popular, saw the need for a precise record of variations in atmospheric CO2.1 Studies of gases trapped in polar ice, pioneered by Swiss and French teams of scientists led by Hans Oeschger and Claude Lorius, extend the record back in time and indicate that the modern rise in CO2 began in the early part of the 18th century.
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From page 87... ...
~340 V o 350 330 C~ o V 320 310 - ~I I 1 1 1 1 _ _ , ~_ _ ~_ _ ,' _ _ ,lIrIr _ _ -~r _ ~-~r ,,~,~ r ~ r" I . I I , I I I I 955 1965 ls75 1985 1095 Year FIGURE 2 Monthly averages of the concentration of CO2 at the South Pole (Keeling and others 1994~.i 87
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C) FIGURE 3 CO2 concentrations over the past 1,000 years from ice-core records (D47, D57, Siple, and South Pole)
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We know that a portion of the carbon emitted by burning fossil fuel will remain in the atmosphere and that some fraction will be taken up by the ocean. A major uncertainty concerns the importance of exchange between the atmosphere and the combination of the terrestrial biosphere and soils.
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Offsetting, higher temperatures could enhance decomposition of organic matter in soils, resulting in a net source of CO2. Higher concentrations of CO2 and industrial sources of fixed nitrogen and sulfur could contribute to increased growth of vegetation, representing a sink for CO2.
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From page 91... ...
of biosphere-soil organic carbon to the observed change. Given a measurement of the change in the abundance of atmospheric CO2 and information on the contribution of burning of fossil fuel and oxidation of organic carbon in soils and the biosphere to this change, we can obtain empirical estimates of the quantity of carbon transferred from the atmosphere to the ocean and of the net exchange of atmospheric carbon with the biosphere and soil.
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From page 92... ...
On a global basis, it appears that in the early years of the 1990s the carbon content of soils and the terrestrial biosphere increased at an annual rate of close to 2 x 109 tons per year.4 From an analysis of gradients in CO2 and O2 observed between the Northern and Southern hemispheres, R.F. Keeling and associates4 concluded that the growth of the biosphere-soil reservoir in the 1990s occurred primarily in the north.
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From page 93... ...
layer of snow at the South Pole. Analysis of the firn data indicates that the biosphere-soil system played a much smaller role in the global budget of atmospheric CO2 over the period 1977-1985 than it did in the 1990s; trends in CO2 and O2 observed in the earlier data can be attributed straightforwardly to the influence of fossil-fuel combustion without invoking a role for either the biosphere or soil.
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We can account for all the existing constraints if we assume a persistent sink for CO2 associated with uptake of carbon by the biosphere-soil system at the middle latitudes of the Northern Hemisphere. The analysis of R.F.
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provide independent support for the existence of a middle-latitude Northern Hemisphere sink for CO2.8 Net ecosystem exchange of carbon varied from a low of -1.4 tons per hectare
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The sink for CO2 at northern middle latitudes could be temporary and likely to diminish in importance as the biosphere-soil system approaches a new steady state reflecting mixed current patterns of land use. IMPLICATIONS FOR THE FUTURE Soils at high latitudes provide an important reservoir for organic carbon between 200 billion and 500 billion tons of carbon.~-~3 The eddy-correlation method used to study exchange of carbon between the atmosphere and Harvard Forest has been applied also to the carbon balance of a mature black spruce forest in central Canada.~4 It was found that decomposition of organic carbon in soils of this system resulted in a small but important net source of CO2 emission to the atmosphere 0.4 ton of carbon per hectare per year inl9941996.
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From page 97... ...
Atmospheric gas concentrations over the past century measured in air from firn at the South Pole. Nature 1996;383, 231-5.
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From page 98... ...
On the whole, however, current climate models do a reasonably good job of simulating the average large-scale seasonal distribution of climate. One important application of coupled models in recent years has been in simulating the climatic consequences of increased CO2 concentration in the atmosphere.
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is trying to move from the genome scale to the organism scale. We know something about the individual components of climate models, but we are not very clever in diagnosing the behavior of the coupled climate system we cannot point to an error as having specific causes.
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DOE has been a leader in trying to explain how to use interaction of economic models with climate models to produce information useful to policy-makers and the public. Now that we understand most aspects of the climate system, including the effects of burning fossil fuels and other climatic forcings, we should not just have a simple view.
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In 1830, the British geologist Charles Lyelli published the first volume of his classic text, Principles of Geology, * in which rational hypotheses were developed to explain geologic formations.
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Hence, the oxygen in the earth's atmosphere is fossil oxygen and reflects, in part, the burial and sequestration of fossil phytoplankton carbon in the oceans. For carbon to be buried and oxygen evolved, phytoplankton production must not have been in equilibrium with oxidation processes; that is, there must have been a change in the biologic pump on geologic time scales.
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From page 103... ...
As Michael McElroy stated, ice-core data clearly indicate that current atmospheric concentration of CO2 are about 30% higher than at any time in the last several hundred thousand years. We do not completely understand climate-change processes in the geologic past, but if the consensus interpretation of the climatic forcings and feedbacks during the Holocene is even roughly correct (I assume that the consensus interpretation of the glacial-interglacial forcing is based on Milankovich cycles, with a feedback on ocean chemistry and biology that led to changes in atmospheric CO2)
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