The Rising Tide

Global Warming And World Sea Levels

Lynne Edgerton

• Publisher: Island Press
• Year: 2013
• Print ISBN:
  9781559630672
  9781559630689
• eBook ISBN:
  9781610914710
• Topic: Biological Sciences
• Subtopic: Meteorology & Climatology
• Index: Biological Sciences

The Rising Tide is the first analysis of global warming and world sea level rise. It outlines state, national, and international actions to respond to the effects of global warming on coastal communities and ecosystems.

Chapter 1

GLOBAL WARMING: FACTS AND IMPLICATIONS

In recent years, activities such as burning fossil fuels, leveling forests, and producing synthetic chemicals such as chlorofluorocarbons (CFCs) have unleashed into the atmosphere large quantities of carbon dioxide (CO₂ and other “greenhouse” gases. These gases are warming the earth at an unprecedented rate. If current trends continue, they are expected to raise the earth’s average surface temperature by at least 1.5° to 4.5° C, or more, in the next century—with warming at the poles perhaps two to three times as large as warming at the middle latitudes.¹

Is It Certain to Occur?

While large uncertainties remain about the timing and ultimate magnitude of climate change, recent research supports the fundamental understanding of the greenhouse effect that has emerged over the last decade. There is little dispute that there has been a significant increase in the global concentrations of heat-trapping gases during the last century. And the overwhelming conclusion from the body of published scientific literature is that this greenhouse gas buildup poses enormous risks.

An unusual aspect of the issue, however, is that the atmospheric warming observed over the past decade does not yet exceed historical natural climate variations, although the five global-average warmest years in the past century occurred in the 1980s. Thus policymakers are faced with considerable uncertainties. There is worry that current estimates of future warming may be too high, that the uncertainties in climate computer models may make action premature, that climate-stabilizing (negative) feedbacks have been omitted from current models.

Even assuming the legitimacy of these concerns, however, the mainstream scientific view of the greenhouse effect is not based solely on models. It is supported by observations of other planets, seasonal variations in the earth’s climate, and, perhaps most important, on long-term changes in the earth’s climate over the last 160,000 years. This evidence, in addition to model results, has been reviewed by numerous national and international scientific bodies—including the National Academy of Sciences, the Scientific Committee on Problems of the Environment, NASA’s Goddard Institute for Space Studies, NOAA’s Geophysical Fluid Dynamics Laboratory, and various laboratories of the Department of Energy (DOE). In an August 1990 report, the Intergovernmental Panel on Climate Change established by the United Nations Environment Program and the World Meteorological Organization summarized the scientific facts of which it is certain, as follows:

• There is a natural greenhouse effect that already keeps the earth warmer than it would otherwise be.
• Emissions resulting from human activities are substantially increasing the atmospheric concentrations of the greenhouse gases: carbon dioxide, methane, chlorofluorocarbons, and nitrous oxide. These increases will enhance the greenhouse effect, resulting on average in an additional warming of the earth’s surface. The main greenhouse gas, water vapor, will increase in response to global warming and further enhance it.²

With regard to temperature observations, there are two key points. First, numerous reviews have reaffirmed that after correcting for urban heat islands and other potential systematic errors, there has been a statistically significant global warming of about 0.5° C over the last century. The U.S. temperature record shows less warming than the global average, but its statistical significance is marginal. This finding should come as no surprise, for the United States represents only 1.5 percent of the area of the earth and there is no inconsistency between a global warming and small regions of the earth showing insignificant warming or even cooling. Second, substantial variability and lags in global temperatures are expected. Because the oceans have a large heat capacity and because natural variability and other climate forcings (such as aerosol loadings) are similar in magnitude to the greenhouse gas buildup so far, the uneven pattern of global warming observed to date is not at all inconsistent with the climate models.

With regard to feedbacks, these uncertainties are recognized by everyone, but they cut both ways. That is, current predictions are at least as likely to be too low as too high.³ Indeed, as recently as 1988, scientific predictions were significantly underestimating the magnitude of the ozone hole. Biological and geochemical feedbacks that are not included in the current models are likely to amplify the warming substantially—by perhaps a factor of 2 or more.⁴ The hypothesis that warming will be substantially mitigated by increased convection that dries the atmosphere has never been published in the scientific literature; in fact, it has been widely rejected by the scientific community.

The risks associated with global warming are clearly enormous. While there will always be respectable scientists who question global warming predictions, they represent a minority within the scientific community.⁵ Although this does not prove that they are wrong, we should not be willing to bet the planet that the National Academy of Sciences, NASA, the Intergovernmental Panel on Climate Change, and other authoritative scientific bodies are wrong and the minority view is right.

There can be no excuse for not pursuing all policy options to reduce greenhouse gases that make economic and environmental sense in their own right. So far the United States is not doing that. Current policies will lead to substantial further accumulation of greenhouse gases. U.S. emissions increased by about 7 percent between 1988 and 1990, and the U.S. share of global emissions, after falling continuously for more than a decade, is now increasing. This is neither necessary nor desirable. This country’s carbon dioxide emissions could be reduced 20 percent by the year 2000, increasing our economic competitiveness, reducing our dependence on imported oil, and lowering our contribution to global warming.

How Is Climate Change Measured?

When evaluating the current status of our climate, scientists compare the historical climate record with current observations and with the predictions of climate models. Since a certain amount of statistical variability in world climate is known to exist, they attempt to separate this natural variability, or “noise,” from the true signals that represent real changes in the system balance rather than random fluctuations. Such work is carried out by developing “signal-to-noise ratios.” The larger the apparent signal compared to the noise, the more certain scientists can be that the global climate is changing.

The key to understanding climate fluctuations often lies in our analysis of these shifts in both the human and proxy records (fossil records). Human records have been useful in elucidating short-term trends, although they are generally considered less reliable if collected before the year 1900. Proxy records are likewise inaccurate, and often incomplete, offering only limited resolution on the scale of hundreds to thousands of years.⁶

On the other hand, ancient natural records provide us with a broad view of our climate’s variability over time and indicate the effects of perturbations to the global climate system. By a variety of methods—including the analysis of gases trapped in air pockets of ancient ice flows and the analysis of oxygen and carbon isotopes from deep-sea sediment cores—scientists have been able to construct a historical record of atmospheric composition and global climates. They have found that global temperatures have varied widely throughout time and that sea levels have varied concurrently. Past climate changes, they hypothesize, have historically ensued from the combination of (1) periodic variations in the earth’s orbit and changes in solar output that influence the distribution and amount of energy the earth receives from the sun, (2) catastrophic events such as meteorite impacts, volcanic eruptions, or changes in oceanic circulation, and (3) ongoing biological processes. Recent measurements indicate that humans have the ability to alter climate significantly as well.⁷

By comparing historical data obtained from air bubbles trapped in ancient ice with current observations, changes above normal fluctuations in the ratios of certain atmospheric gases have been documented. Among these gases are carbon dioxide, methane, and nitrous oxide, which until the last few centuries had existed in a stable natural balance for millennia due to biological and chemical processes. Over geological time, these major gases have played a vital part in regulating the earth’s climate.

The Greenhouse Effect

Water vapor, carbon dioxide, methane, nitrous oxide, and ozone comprise the natural fraction of what are called the greenhouse gases. These gases delay the escape of infrared radiation from the earth into space, thus causing a general climatic warming known as the greenhouse effect (by analogy to the warming that occurs in a greenhouse). Scientists have stressed that this is a natural process—indeed, the earth would be 33° C (63° F) cooler than it is presently if the greenhouse effect did not exist.⁸

Human activities are now rapidly intensifying this natural greenhouse effect. Carbon dioxide concentrations have increased 25 percent since preindustrial times, methane concentrations have doubled, and chlorofluorocarbons have been introduced into the atmosphere for the first time. Human activities have not only directly added these greenhouse gases to the atmosphere, but they have greatly altered the chemistry of the global atmosphere by increasing the production of tropospheric ozone and decreasing the natural destruction of methane, thus further enhancing the greenhouse effect. The rate at which the greenhouse effect is intensifying—the rate of climate “forcing”—is now more than five times what it was during the last century.⁹

During the 1980s carbon dioxide accounted for approximately 55 percent of the climate forcing, while CFCs accounted for about 24 percent. Methane and nitrous oxide together contributed approximately 21 percent. We turn now to the empirical evidence and its implications.

THE INCREASE IN CARBON DIOXIDE

The increase in atmospheric carbon dioxide is due primarily to fossil fuel combustion (coal, oil, and gas) and deforestation. The most precise measurements of atmospheric CO₂ were begun at Mauna Loa, Hawaii, in 1958. (See Figure 1.1.) The rate of observed CO₂ increase since that time has closely followed fossil fuel consumption rates; consequently, the strong implication is that this source dominates any natural source and overwhelms any natural processes of removal.¹⁰

Global deforestation is believed to be another important contributor to the increasing concentration of carbon dioxide.¹¹ As land is cleared or burned for agriculture, or harvested for timber, CO₂ is released into the atmosphere from the decay and oxidation of the carbon that had been incorporated in the trees and soil organic matter. These processes are estimated to contribute 10 to 30 percent of anthropogenic CO₂ emissions. Although the future contribution of deforestation or reforestation to atmospheric CO₂ levels could be significant, these aspects of the global carbon budget are little understood and have thus far been inadequately modeled. Control of future CO₂ concentrations would benefit substantially from strengthened research in this area.

If nothing else in the earth’s climatic system changed, a doubling of CO₂ would raise the global average temperature 1.2° C.¹² The earth’s climatic system, however, is highly complex: A warming from increasing CO₂, for example, causes corresponding changes in other parts of the system, s...

Table of contents

• About Island Press
• About NRDC’s Atmosphere Protection Initiative
• Title Page
• Copyright Page
• Dedication
• Epigraph
• Table of Contents
• FOREWORD
• PREFACE
• ACKNOWLEDGMENTS
• Chapter 1 - GLOBAL WARMING: FACTS AND IMPLICATIONS
• Chapter 2 - PLANNING FOR THE FUTURE
• Chapter 3 - THE MAJOR EFFECTS
• Chapter 4 - FEDERAL POLICY
• Chapter 5 - CHALLENGES FACING THE COASTAL STATES
• Chapter 6 - INTERNATIONAL EFFECTS AND POLICIES
• Chapter 7 - FINDINGS AND RECOMMENDATIONS
• Appendix A: - The 1989 Cairo Compact
• Appendix B: - A Draft Protocol for International Cooperation
• Appendix C: - CZMP Responses to Sea Level Rise
• Appendix D: - Alternative Policy Responses to Sea Level Rise
• Appendix E: - Excerpts from Maine’s Sand Dune Rules
• NOTES
• BIBLIOGRAPHY
• INDEX
• ABOUT THE AUTHOR
• ALSO AVAILABLE FROM ISLAND PRESS
• ISLAND PRESS BOARD OF DIRECTORS