Economic Issues In Global Climate Change

Agriculture, Forestry, And Natural Resources

John M. Reilly

• Publisher: CRC Press
• Year: 2019
• ISBN:
  9780429715402
• Edition: 1
• Topic: Biological Sciences
• Subtopic: Ecology
• Index: Biological Sciences

This book provides a snapshot on economic thinking about global change and provides a starting point for researchers for evaluating the economics of global change in the context of agriculture, forestry, and resource issues. It attempts to rectify the scarcity of economic analysis in global change.

PART ONE
Overviews

1
The Science of Global Change: An Illustrated Overview

Daniel L. Albritton¹

Introduction

This summary addresses four points: (1) the scientific scope of global change, (2) the characteristics of the three major components of the global system, (3) the status of the current scientific understanding of global change, and (4) what appear to be the most fruitful interactions between science and economics. The comments regarding the last point are the personal viewpoint of a scientist. Other chapters in this volume elaborate on the science-economics interaction from the economist's perspective.

The Global System: What is the Nature of the Science-Economics Arena?

It is useful to think of the global system in terms of forcings, physical processes, physical responses, biological processes, and ecosystem responses (Figure 1.1). A variety of forcing agents activate numerous physical processes that move the global system to a new physical state. The latter, in turn, induces numerous biological processes that cause changes in the world's ecosystems.

The aim of global-change scientific research is to understand the role of humans in the forcing agents and to build a predictive understanding of how the planet will respond to these forcings. Humans and their economic affairs enter into public-welfare decisions associated with the forcing agents and into similar decisions associated with the physical and biological responses. Specifically, there are costs associated with reducing our forcing of global change, and there are costs associated with coping with the impacts of global change.

Ideally, we want to know enough—both about the global system and the economic systems—to optimize the relation between those two costs. This should be the joint aim of the partnership of the physical sciences and economics, toward which this volume is an excellent start.

Components of the Global System: Three Types

Global-Change Forcing Agents—Human-Influenced and Natural

Radiatively Important Gases. Several trace gases capture part of the surface heat energy that is radiated outward toward space and then radiate it back to the surface, which is the greenhouse effect (Figure 1.2). It is a natural part of the global system. However, over the past century, human activities have increased the atmospheric abundances of gases such as C0₂, methane, chlorofluorocarbons, nitrous oxide, and lower-atmospheric ozone. Thus, the trace-gas emissions associated with human activities have perturbed the natural greenhouse balance of the planet, leading to the possibility of global warming.

Sun-Earth Interactions. The sun is, of course, the driver of the climate system of the Earth. In short, we are a "solar-powered" planet. The variation of sunlight causes daily, week-to-month, seasonal, and long-term variations. The first three variations are clearly discernible. However, it is by no means clear how sun-atmosphere couplings can introduce changes occurring over one to two decades, and the topic is one of lively current debate. The effort to find such mechanisms is driven not only by the need to forecast such natural swings of the climate, but also to aid the search for and the understanding of the human-induced changes that are superimposed on this natural variation.

Physical Response Processes: The Climate "Machine"

The physical climate system is, in many ways, analogous to many of our machines (Figure 1.3).

Physical Air-Sea Coupling (a "Part"). Wind stress on the ocean surface influences evaporation, which influences one of the key greenhouse gases—water vapor. Such a process must be characterized if we are to build a working picture of the greenhouse effect.

Water Vapor Feedback ("Linkages"). Many of the parts are coupled cyclically. For example, a surface warming will cause more evaporation, leading to higher concentrations of water vapor. This, in turn, will increase the greenhouse trapping of radiation, which would then would lead to even higher surface warming. The cycle illustrates "positive feedback," i.e., a reinforcement that amplifies the warming phenomenon.

El Niño-Southern Oscillation (a "Subassembly"). In the large expanses of the tropical Pacific, a major subsystem of the planet marches to its own drummer. The atmospheric circulation pattern (upward motion in the western Pacific, matched by downward motion in the eastern Pacific) waxes and wanes on approximately a 26-month cycle. During the high peaks and deep valleys of this variation, U.S. weather and habitation and fishing along the eastern coasts of the Pacific are severely affected. Hence, considerable research is directed toward building a predictive capability for this major subsystem.

Oceanic Thermal Inertia (a "Warm-up" Period). The main delay in a warming of the Earth's surface is the long time that it takes to warm the oceans. The nature of that delay depends largely on how warm surface water is carried into the colder deep ocean and vice versa. Thus, the large-scale circulation patterns of the ocean, which are difficult to observe, are a key factor in the timing of greenhouse warming.

Biological-Response Processes

Biotic systems have three scales of responses (Figure 1.4).

Microscale. A key example of very-small-scale processes is the uptake of C0₂ via the stomata of leaves. Carbon dioxide can stimulate plant growth, showing that there is an "upside" to what is the large "downside" of this major greenhouse gas. However, there is high variation in the responses of different plants, making it difficult to assess the overall benefit.

Middle Scale. An important example of local responses to temperature change is forest composition. Several climatic processes influence the makeup of forest-tree types: rainfall—regeneration; moisture levels—forest fires; and warmer winters—pest mortality. Forest responses via such mechanisms can be large, even to small changes in physical variables.

Macroscale. Several ecosystems demonstrate that long-term climatic changes can produce large-scale changes in the landscape: drier climes and forest migration. The understanding of these processes is, however, largely based on sparse and empirical data.

Knowns and Unknowns: How Well Do We Currently Understand this System?

The few examples above illustrate the complexity of the Earth system, with its variety of forcing agents, diversity of the "wheels" and "cogs" that are the processes that make up the planetary machine, and the new physical and biological states that are reached. Although we have learned much, there is still much to learn (Figure 1.5). The status of the science is varied, ranging from "certainties" to "unknowns," which are arranged here in that order. There are policy and economic implications about what we do know and about what we do not know.

The Natural Greenhouse Effect (a ''Certainty'')

In terms of basic physics, if a body is bathed in visible radiation, it warms up and radiates infrared energy (heat) (Figure 1.6). In terms of our planet Earth, it works the same way, except the atmosphere introduces a "blanket" that traps part of that outbound radiation. It is not the common atmospheric gases—nitrogen and oxygen—that are the wool in the blanket; it is the minute concentrations of gases such as water vapor and CO₂.

There are several key points regarding the greenhouse effect (Figure 1.7): (1) it is a natural part of the Earth; (2) water vapor and C0₂ have been part of the atmosphere for millions of years; and (3) their presence has produced an average surface temperature of =15 °C. Without them, the average temperature would be = -15 °C, and our planet would be shrouded in ice.

Thus, there is no doubt that the greenhouse effect is real. We understand its basic principles. So, what is the problem and issue regarding the greenhouse effect? It is this: just recently (geologically speaking), we have begun to alter it.

Trace-Gas Forcing of the Radiation Balance (a "Confident Calculation")

In the 1950s, the major gas causing radiative forcing was C0₂, with the combined effect of all the of the other gases amounting to only one-third as much. However, by the 1980s, not only had the total radiative forcing increased fourfold, but also C0₂ was then only about half of it (Figure 1.8). This demonstrates that, from a scientific perspective, policy and economics should consider ail of the greenhouse gases and their relative contributions.

Predictions of Future Planetary Responses (Application of Our "Best Tools")

To predict future changes as a result of current forcings requires a "working replica" of the global system (Figure 1.9). These are the global models that reside in large computers and are intended to be the best "replica models" of the complex system itself. While admittedly not perfect miniatures of the system, the best attempts have obviously been made to incorporate the known major processes (e.g., both the warming and cooling roles of clouds and the time delay introduced by ocean circulation).

Several future forcing scenarios are entered into to these models, e.g., "business as usual" (increasing greenhouse gases) and "bite the bullet" (decreasing greenhouse gases). Global models, as our best tools, then yield predictions for each of the scenarios. The results of those predictions include values for variables that are of human interest, e.g., temperature, rainfall, and sea level. The range of these values can be compared with past natural variation—worse or less? They can also be used to search for the first signs that these predictions are actually borne out.

Some predictions from the recent Intergovernmental Panel on Climate Change (IPCC) report are given here (Figure 1.10). The business-as-usual scenario predicts that global-average temperatures will increase 1 °C by 2025 and 3 °C by 2100. Sea level will increase 0.2 m by 2030 and 0.65 m by 2100. If severe cuts in greenhouse-gas emissions were to be made, the above values would be reduced by factors of 2 to 5. Generally, such changes would not be accomplished smoothly because of superimposed natural variation. The continents would warm faster and more than would the oceans. It is important to note that it is currently believed that some warming is very likely.

The View of the Past ("Judgment Calls")

The geological record contains the climate history of the planet. Proxy indicators such as tree rings and fossils give estimates of past temperature variations. They show that, over the past 10,000 years since the last Ice Age, the planet's average temperature has varied 1-3 °C, thereby providing a measure of the natural swings in the planet's surface temperature (Figure 1.11). For the past several hundred years, we have been "rebounding" from the Little Ice Age, which was the most recent minimum in temperature.

Direct temperature measurements have been made for the past century and a half. These data show the details of the most recent end of the warming trend—an increase of =0.45 °C over that span. It has occurred largely in two upward jumps, the first in the 1920s and the second in the 1980s. Do we know why these temperature changes have occurred?

What Cannot Be Said ("Unknowns")

The recent 0.45 C warming can neither confirm nor deny whether a human-influenced warming has occurred. Because the predicted greenhouse warming (=0.7 °C) is so similar in magnitude to unexplained natural variation, the signal does not stand out clearly from the noise (Figure 1.12). Thus, the jury is still out on whether a greenhouse warming has or has not occurred.

The current models are not a...

Table of contents

• Cover
• Half Title
• Title
• Copyright
• Contents
• Acknowledgments
• Preface
• PART ONE Overviews
• PART TWO Broader Perspectives
• PART THREE Agriculture, Natural Resources, and Global Change
• PART FOUR Forestry and Global Change
• PART FIVE International Perspectives of Global Change
• PART SEVEN Data and Research Priorities
• Index