Challenge of Global Warming

Dean E. Natural Resources Defense Council, Dean E. Abrahamson

• Publisher: Island Press
• Year: 2013
• Print ISBN: 9780933280861, 9780933280878
• eBook ISBN: 9781597269254
• Topic: Biological Sciences
• Subtopic: Environmental Science
• Index: Biological Sciences

Challenge of Global Warming examines the causes and effects of global climate change.

PART I

THE CHALLENGE OF GLOBAL WARMING

Chapter 1

GLOBAL WARMING: THE ISSUE, IMPACTS, RESPONSES

Dean Edwin Abrahamson

THE ISSUE

Humanity is conducting an unintended, uncontrolled, globally pervasive experiment whose ultimate consequences could be second only to nuclear war. The Earth’s atmosphere is being changed at an unprecedented rate by pollutants resulting from human activities, inefficient and wasteful fossil fuel use and the effects of rapid population growth in many regions. These changes are already having harmful consequences over many parts of the globe.

—Toronto Conference statement, June 1988

This analogy between the consequences of nuclear war and atmospheric pollution was made not by idealistic, scientifically innocent environmentalists, but by the more than 300 policymakers and scientists from 46 countries, United Nations organizations, other international bodies, and nongovernmental organizations who attended a major international conference sponsored by the government of Canada. The Toronto Conference statement, included in full in Chapter 3, illustrates that it is now clearly within our power not only to alter the planet beyond comprehension within a few hours by using nuclear weapons, but also within a few decades by destroying the earth’s life-support systems and radically changing climate by contamination of the air and water with the residuals of production.

Global climate is changing because of the buildup in the atmosphere of carbon dioxide (CO₂), methane, nitrous oxide (N₂O), the CFCs (powerful greenhouse gases as well as destroyers of stratospheric ozone), and other greenhouse gases produced by fossil fuel burning, by deforestation (discussed in detail in Chapter 5), and by producing food for the rapidly increasing global population.

The consequences of the global heating which would result if present release rates of the major greenhouse gases are maintained for only a few more decades would be catastrophic if our present scientific understanding is even approximately correct, and the resulting climatic change would be irreversible. (See the report of the 1987 Villach-Bellagio conferences in Chapter 7.) It is now known that a warming of several degrees, greater than previously experienced in human history, could occur within the next few decades—a time which is short compared with the lifespan of a tree or a man. Major changes will result in ecological, economic, and social systems as all are in delicate balance with their environments which in turn are dependent on climate. No one can now describe the precise nature of these changes—in part because of the technical demands of climate modeling and in part because of the impossibility of predicting the choices which will be made within the next 50 or so years—but change there will be. Although the crystal ball is too cloudy to reveal the details, the general course of climatic change is well understood (see Chapter 8).

Studies of past climate changes can tell us something about the response of forests. As the last ice age retreated, the earth warmed, slowly, for several thousand years. This change completely rearranged the face of the United States. Tree species that grew in Ohio and Michigan migrated far into Canada, and other tree species from the Deep South moved north into Ohio and Michigan.

If we allow emissions of CO₂ and the other greenhouse gases to continue unabated, the earth will warm five to ten times faster than it did during the retreat of the last ice age. Many trees cannot migrate much faster than they did as the earth slowly warmed following the last ice age. By the time a tree matures enough to produce seeds, the climate will be unfavorable for those seeds to take hold and produce the next generation. We thus could be heading toward a country almost devoid of young trees, a country given over to shrubs that tolerate a wide range of conditions—a sumac world.

As go the forests, so go the other species, animal and plant, supported by them. As Robert L. Peters suggests in Chapter 6, the most likely outcome is widespread extinction of species. The U.S. National Research Council has concluded: “It seems likely that the impacts of climatic change will fall most severely on immovable, and therefore inflexible, elements of both natural and man-made infrastructures. . . . National parks and biosphere reserves are usually established to preserve some asset of unique physical or biological importance, often depend on climatic factors, and cannot be easily removed or replaced.”¹

Each 1°C of global warming will shift temperature zones by about 100 miles. A continuation of present trends in the emission of CO₂ and the other greenhouse gases is expected to result in additional global heating of at least 2°C by the year 2030. Were this to happen, the climate upon which, for example, Yellowstone Park’s ecosystem depends will have moved—the place called Yellowstone will be occupied by a different ecosystem. All the effort which has gone into the park from its creation through fighting the 1988 fire will have been in vain if global warming is not limited. Other parks, refuges, and wilderness will also be affected by warming, by changes in water balance, or by saltwater intrusion.

Continued global heating will also increase sea level by 1 to possibly 3 meters within the next hundred years (detailed in Chapter 12). This sea-level rise would be sufficient to inundate most salt marshes and coastal wetlands, change the character of the Everglades, push barrier islands further toward the present coast, and contaminate coastal aquifers. Reduced summer soil moisture would result in the loss of freshwater wetlands, reduced stream flows, and further lowering of aquifers. The consequences would include loss of wetlands habitat, reduced water quality, and increased concentrations of toxic wastes.

Coping with global heating and global climatic change may be the ultimate environmental challenge. If we fail to reduce emissions of the greenhouse gases, the climate change expected within the next few decades will be sufficient to jeopardize resources which much of the present environmental legislation is designed to protect.

The Brundtland Report details the challenge of making room for a world population of 8 to 14 billion people within the next century and a severalfold increase in world economic activity. A world with a doubled or tripled human population, with a severalfold increase in consumption, and with greenhouse gases, industrial pollutants, and other assaults on the environment proportional to those of today is not only virtually unimaginable, but impossible. If societies attempt a severalfold increase in economic activity described in the Brundtland Report using the present means of production, increasing emissions of greenhouse gases will have consequences similar to those of nuclear war. We have no alternative but to devise means of production which can provide the necessary goods and services to a growing population without causing irreversible biotic impoverishment.

THE GREENHOUSE EFFECT

Global warming has reached a level such that we can ascribe with a high degree of confidence a cause and effect relationship between the greenhouse effect and the observed warming.

—James Hansen, NASA climatologist, 1988

The greenhouse effect results from the buildup in the atmosphere of gases which absorb heat (long-wavelength infrared radiation), a topic considered in detail by Gordon MacDonald in Chapter 9. To maintain a constant average temperature, the earth must radiate heat to space. Greenhouse gases like CO₂ and methane absorb a part of this heat energy and reradiate it back to the surface of the planet, thereby effectively trapping it in the lower atmosphere. This process raises the temperature of the atmosphere near the earth, which in turn raises sea level, increases evaporation and precipitation to affect global cloud cover, and thereby alters the distribution of climate across the surface of the planet. An increase in average global temperature of 0.7°C has already been measured, and present rates of emission of greenhouse gases are committing the earth to an additional warming of about 0.3°C per decade.

It is because they trap heat like glass in a greenhouse that these gases received their name—the greenhouse gases. They are vitally important for life. Venus, with an atmosphere rich in CO₂, has a greenhouse effect of between 400 and 500°C, and Mars, with its thin atmosphere, only a few degrees. Earth has a natural greenhouse effect due to the presence of CO₂ and water vapor. If Earth’s atmosphere did not contain these gases, its temperature would be 33°C lower. The natural level of these gases make life as we know it possible.

Increasing them beyond today’s level will cause the climate to diverge markedly from its present state. Climatic zones shift by about 100 miles for each 1°C of global warming. Sea level will rise all over the earth. Major weather patterns—for example, the tropical monsoons and jet streams—are altered. A warming of about 4°C, to which we may be committed in less than 50 years, would result in an ice-free Arctic Ocean which will not only devastate arctic ecosystems but will further change climate and weather. A warming of this extent could also begin an irreversible disintegration of the West Antarctic ice sheets which would result, within a few hundred years, in a further rise in sea level by at least 6 meters.

ABOUT THE GREENHOUSE GASES

Carbon dioxide, the single most important greenhouse gas, accounts for about half of the warming that has been experienced as a result of past emissions and also for half of the projected future warming. The present concentration is now about 350 parts per million (ppm) and is increasing about 0.4% (1.5 ppm) per year, retaining an additional 3 billion tons (10⁹ tons or GT) of carbon per year. For a very long period of time before the industrial age, the atmospheric concentration was essentially constant. Beginning about 1850, however, the CO₂ level began to rise, due in large part to the industrial burning of first coal and then oil and natural gas. The atmospheric CO₂ level in 1850 was probably about 270 ppm; thus it has already increased by about 30%. Human activities are now causing at least 7 billion tons of carbon,² as carbon dioxide, to be released into the atmosphere. Fossil fuel use releases about 6 billion tons per year to the atmosphere. In addition, the clearing and burning of forests causes the pool of carbon which has been tied up in trees to be released. Deforestation is in part the result of population expansion in the tropics and the use of land for agriculture and wood for energy. The desire of developed countries for inexpensive meat and forest products is another major contributor to deforestation. Each year a land area the size of Belgium is deforested, resulting in the transfer from forests to the atmosphere of between 1 and 3 billion tons of carbon per year, as detailed by George M. Woodwell in Chapter 5.

If present trends in the release of CO₂ to the atmosphere continue, the preindustrial level of CO₂ will increase another 30% in 50 years, and then double about the year 2100. In principle, there are no obvious physical constraints to limit this rise. The remaining amounts of oil and gas are quite small, but the amount of coal that is subject to exploitation is essentially unlimited. Economics and policy on emission of greenhouse gases will govern how rapidly CO₂ builds up before either humankind or nature acts to stabilize the atmospheric burden of greenhouse gases.

In addition to CO₂, another 20 or so greenhouse gases have been identified (detailed by Peter Ciborowski in Chapter 14). At present the most important are methane (CH₄), the chlorofluorocarbons CFC-11 and CFC-12, nitrous oxide (N₂O), and ozone (O₃) in the lower atmosphere (see Chapter 15).³ Taken together, these other greenhouse gases are responsible for at least as much global warming as is CO₂, and perhaps more. At present methane is the most important of these gases, followed closely by CFC-12.

Methane is produced in flooded fields and waterlogged soils, in rice paddies, in the guts of cattle and other fauna, in landfills, and in coal seams. It is also released as a result of forest clearing, venting in association with oil production, and leakage from natural gas pipelines. Atmospheric methane concentration is now increasing at about 1% per year (see Chapter 17). CFC-12 is primarily used as the working fluid in refrigerators and air conditioners. CFC-11 is used mainly in plastic urethane foams. The CFCs in general are used in spray cans, forming plastic foams, and as solvents. (See Chapter 20.) Nitro...

Table of contents

• Title Page
• Copyright Page
• Dedication
• Table of Contents
• PREFACE
• INTRODUCTION - Senator Timothy E. Wirth
• PART I - THE CHALLENGE OF GLOBAL WARMING
• PART II - GLOBAL WARMING: BIOTIC SYSTEMS
• PART III - GLOBAL WARMING: PHYSICAL IMPACTS
• PART IV - THE GREENHOUSE GASES
• PART V - POLICY RESPONSES
• FOR FURTHER READING
• FOR FURTHER INFORMATION
• INDEX
• ABOUT THE AUTHORS
• ALSO AVAILABLE FROM ISLAND PRESS