Advances in Energy Systems and Technology

Volume 4

Peter Auer, David Douglas

• Publisher: Academic Press
• Year: 2013
• Print ISBN: 9780120149049
• eBook ISBN: 9781483191287
• Topic: Tecnologia e ingegneria
• Subtopic: Ingegneria generale

Advances in Energy Systems and Technology, Volume 4 covers articles about energy systems and technology. The book discusses articles about atmospheric carbon dioxide (CO2), including anthropogenic sources of CO2, the effects of increased atmospheric CO2 on climate, and the effects of climate changes and direct CO2 impacts. The text also describes automobile pollution control with regard to complex chemical and physical processes that take place during combustion in automobile engines and the reduction of the levels of pollution emitted by internal combustion engines. The statistical perspective on world oil resources, as well as the historical perspective on electricity and energy use and on the relationship of electricity to gross national product, is also considered. The book further explores the relationship between economic activity and energy use and uninterrupted trend toward increasing electrification in the United States. Professional workers in the field of energy systems and technology as well as those of university students at the graduate or advanced undergraduate level will find the book useful.

A Current View of Atmospheric CO₂

Ralph M. Rotty, Institute for Energy Analysis, Oak Ridge Associated Universities, Oak Ridge, Tennessee

Publisher Summary

This chapter presents a current view of atmospheric carbon dioxide (CO₂). CO₂ is required in the atmosphere for life to exist. It is necessary in the photosynthesis process and also provides a temperature-regulating mechanism that gives the planet a thermal regime suitable for human habitation. CO₂ is relatively transparent to visible light from the sun but absorbs energy in the infrared wavelengths of the earth’s radiation to space. This suggests that significant changes in precipitation patterns in several critical agricultural areas of the world may take place. The natural exchanges between the terrestrial biosphere and other elements of the global carbon cycle are many times larger than the current anthropogenic fluxes. There is no clear understanding, however, of the changes that have occurred in the fluxes between the biosphere and the atmosphere as a consequence of the anthropogenic disturbance of the natural quasi-equilibrium. Great uncertainty remains in connection with the full effects of atmospheric CO₂ levels at elevated levels. Therefore, specifying a limit on a level to be avoided is impossible on the basis of present knowledge. The most effective and realistic way to limit atmospheric CO₂ concentrations is to curtail fossil fuel combustion. For such action to become necessary, having alternatives is a requirement for preventing disaster.

I. Introduction

II. Anthropogenic Sources of CO₂

A. Fossil Fuel Sources

B. Forest Conversion as a CO₂ Source

III. How Much Remains in the Atmosphere?

A. The Atmospheric Fraction

B. The Carbon Cycle

IV. Effects of Increased Atmospheric CO₂ on Climate

A. Climate Models

B. Studies of Past Climates

C. Verification of a Climate Change

V. Effects of Climate Changes and Direct CO₂ Impacts

A. Melting of Polar Region Ice Sheets

B. Impacts on Natural Ecosystems

C. Direct Impacts of CO₂ on Photosynthesis.

D. Impacts on Global Agriculture

E. Impacts on the Oceans

F. Impacts on the Carbon Cycle

G. Direct CO₂ Impact on Humans

VI. Projections and Conclusions

References

I INTRODUCTION

In the natural biogeochemical processes that take place on our earth, vast amounts of carbon are exchanged among living things, oceans and freshwater, the atmosphere, and components of the solid earth itself. Superimposed on the natural processes are the activities of man. During the nineteenth and twentieth centuries the combination of human population growth and modern technology has resulted in an anthropogenic release of carbon from storage as carbon dioxide. Although the rates of anthropogenic release are still small in relation to the natural exchanges, they are no longer negligible.

Carbon dioxide is not usually regarded as a pollutant in the atmosphere, because it exists there naturally at concentrations in the neighborhood of 0.03%. In fact, carbon dioxide is required in the atmosphere for life to exist. Not only is carbon dioxide necessary in the photosynthesis process, on which all life (directly or indirectly) depends, but atmospheric carbon dioxide also provides a temperature-regulating mechanism that gives our planet a thermal regime suitable for human habitation. Without enough carbon dioxide in the atmosphere, the earth would be ice covered; and with too much, the earth could be uninhabitably hot.

It is this so-called “greenhouse effect” that causes the concern about the concentration of carbon dioxide in the atmosphere. Certain gases, including carbon dioxide and water vapor, are transparent to energy radiated in some wavelengths while absorbing energy radiated in others. Carbon dioxide is relatively transparent to visible light (energy) from the sun, but absorbs energy in the IR (heat) wavelengths of the earth’s radiation to space. With or without increased CO₂, the energy leaving the earth must be the same as that received from the sun; with increased CO₂ this requires a change in the thermal structure of the atmosphere—increasing temperatures near the surface and decreasing temperatures at higher altitudes. It is this change in the thermal structure that could result in a profound and long-lasting change in the earth’s climate.

This result of increasing atmospheric carbon dioxide suggests that significant changes in precipitation patterns in several critical agricultural areas of the world may take place. The indicated warming near the earth’s surface also suggests that some of the high-latitude ice in both hemispheres might melt, and for the cases of glaciers located on land, one result would be the rising of sea levels. Because substantial time is required to melt enough ice to give a significant rise in sea level, this impact may (for now) be of less concern than the impacts that a global climate change could have on food production.

In thinking about the several scientific aspects of this issue, one is led to four broad areas of inquiry.

(a) What are the anthropogenic sources of carbon dioxide? Fossil fuel combustion is not alone as the source of the observed growth of atmospheric carbon dioxide. Conversion of natural forests to agriculture and other commercial ventures has released (still is releasing, in some areas) carbon from long-term storage. Evidence is mounting that during the past century forest conversion contributed to the atmospheric CO₂ increase a total amount of carbon that is of the same magnitude as that from fossil fuels during the same period (World Meteorological Organization, 1981; Houghton et al., 1983; Richards et al., 1983). Fossil fuel combustion has been increasing rapidly for several decades, and the vast amounts of carbon stored in the recoverable reserves suggest that the proportion of the anthropogenic CO₂ coming from fossil fuels will steadily increase.

(b) The fate of all the anthropogenic CO₂ is not clear. The increase in atmospheric CO₂ accounts for only (2–3) × 10¹⁵ g carbon of the 5 × 10¹⁵ g carbon in the carbon dioxide produced by fossil fuel combustion—the remainder being sequestered in the oceans and in the terrestrial biosphere. If we are to have any predictive capability as to the future carbon dioxide content of the atmosphere, an understanding (including quantitative information) of the fluxes between the several perturbed carbon reservoirs is essential. The time at which CO₂ imposes major impacts on human society depends not only on how fast, and how much, we burn fossil fuel, but also on how much remains in the atmosphere.

(c) Specific changes that are likely to be associated with the general warming near the earth’s surface can be only deduced in rather general terms depending upon crucial climatic variables in key geographical areas. Climate modelers have developed procedures that enable them to depict the major features of climate in mathematical terms. These models show clearly that near the earth’s surface the atmosphere will be warmed and that this warming will be accentuated in high latitudes, but the magnitude of these changes seems small to the uninitiated. It is the more subtle climatic effects of the new atmospheric circulation pattern resulting from the new temperature regime that are significant. Length of the growing season is clearly of great importance in agriculture, but it affects natural ecosystems as well. Confidence in our ability to predict the details of such a new climate remains elusive.

(d) How large must a climate change be and of what nature before human welfare is seriously affected? We know that particular combinations of sunshine, precipitation, and temperature are necessary to produce food, but we do not know the limits to which each of these variables can be pushed by developing new varieties of food crops. Frequent intervals like the “dust bowl” could continue to be very serious even with new varieties developed for drier climates. We do not yet know how much the temperature must rise and how long a time is required to give significant melting of polar ice, or how to make good estimates on the full costs associated with such an event. There are many types of potential consequences from a changed climate; evaluation of these is just beginning. Such evaluations must always be made, however, in contrast with the costs to humanity of taking steps now to avoid the climate change.

Each of these areas of inquiry will be addressed below, but a full appreciation of the issues surrounding increases in atmospheric carbon dioxide can only be obtained by recognizing the interdependence between the areas as well as the independent scientific issues of each area. The sources of CO₂ depend on the working of complex systems of human needs—e.g., adapting to a situation of insufficient water supply may be accomplished either by using more energy for irrigation or by importing water;the fluxes from one reservoir to another in the carbon cycle depend on the amount of carbon being partitioned (i.e., the anthropogenic sources) and on the human activity of destroying or augmenting the reservoirs.

In each of the fo...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Contributors
• Preface
• Contents of Previous Volumes
• Chapter 1: A Current View of Atmospheric CO2
• Chapter 2: Automobile Pollution Control
• Chapter 3: World Oil Resources: A Statistical Perspective
• Chapter 4: An Historical Perspective on Electricity and Energy Use
• Chapter 5: An Historical Perspective on the Relationship of Electricity to Gross National Product
• Index