CONTENTS. Introduction x

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2 CONTENTS Introduction x Chapter 1: Climate 1 Solar Radiation and Temperature 2 The Distribution of Radiant Energy from the Sun 2 The Effects of the Atmosphere 3 Average Radiation Budgets 6 Surface-Energy Budgets 7 Climatology 9 Temperature 9 The Global Variation of Mean Temperature 10 Diurnal, Seasonal, and Extreme Temperatures 11 Temperature Variation with Height 13 Circulation, Currents, and OceanAtmosphere Interaction 14 Short-Term Temperature Changes 17 Atmospheric Humidity and Precipitation 18 Atmospheric Humidity 18 Precipitation 30 Atmospheric Pressure and Wind 56 Atmospheric Pressure 57 Wind 59 Maritime Continent 82 Monsoons 82 Upper-Level Winds 86 Chapter 2: Climatic Classification 102 Approaches to Climatic Classification

3 Genetic Classifications 106 Empirical Classifications 108 The World Distribution of Major Climatic Types 114 Type A Climates 114 Type B Climates 118 Type C and D Climates 123 Type E Climates 130 Type H Climates 133 Chapter 3: Climate and Life 135 The Gaia Hypothesis 136 The Evolution of Life and the Atmosphere 138 The Role of the Biosphere in the EarthAtmosphere System 140 The Biosphere and Earth s Energy Budget 140 The Cycling of Biogenic Atmospheric Gases 143 Bioclimatology 149 Biosphere Controls on the Structure of the Atmosphere 150 Biosphere Controls on the Planetary Boundary Layer 151 Biosphere Controls on Maximum Temperatures by Evaporation and Transpiration 153 Biosphere Controls on Minimum Temperatures 154 Climate and Changes in the Albedo of the Surface 157 The Effect of Vegetation Patchiness on Mesoscale Climates 158 Biosphere Controls on Surface Friction and Localized Winds

4 Biosphere Impacts on Precipitation Processes 160 Climate, Humans, and Human Affairs 164 Chapter 4: Climate Change 168 The Earth System 169 Evidence for Climate Change 174 Causes of Climate Change 176 Solar Variability 176 Volcanic Activity 177 Tectonic Activity 179 Orbital (Milankovitch) Variations 180 Greenhouse Gases 182 Feedback Within the Earth System 182 Human Activities 184 Climate Change Within a Human Life Span 186 Seasonal Variation 187 Interannual Variation 189 Decadal Variation 192 El Niño 193 Climate Change Since the Emergence of Civilization 197 Centennial-Scale Variation 198 Millennial and Multimillennial Variation 200 Climate Change Since the Emergence of Humans 204 Recent Glacial and Interglacial Periods 205 Paleoclimatology 207 Glacial and Interglacial Cycles of the Pleistocene

5 The Last Great Cooling 212 Climate Change Through Geologic Time 213 Cenozoic Climates 214 Phanerozoic Climates 217 The Climates of Early Earth 219 Abrupt Climate Changes in Earth History 223 Chapter 5: Global Warming 227 Causes of Global Warming 230 The Greenhouse Effect 230 Radiative Forcing 233 The Influences of Human Activity on Climate 234 Carbon Sequestrian 249 Natural Influences on Climate 252 Feedback Mechanisms and Climate Sensitivity 260 Climate Research 265 Modern Observations 266 Prehistorical Climate Records 268 Theoretical Climate Models 269 Potential Effects of Global Warming 274 Simulations of Future Climate Change 276 Environmental Consequences of Global Warming 282 Socioeconomic Consequences of Global Warming 286 Global Warming and Public Policy 290 Kyoto Protocol 291 The IPCC and the Scientific Consensus

6 The UN Framework Convention and the Kyoto Protocol 296 Future Climate-Change Policy 299 An Inconvenient Truth 302 Public Awareness and Action 305 Green Architecture 305 Electric and Hybrid Vehicles 316 Biofuels 323 Conclusion Glossary 330 Bibliography 332 Index 339

7 INTRODUCTION INTRODUCTION

8 7 Introduction S 7 ince at least the 1970s, Earth s changing climate has been a popular news topic. Even though scientists have been studying varying aspects of climate for centuries, much about climate remains murky to the general public, and understandably so. The forces that drive the world s climates are complex and dependent on factors as diverse as geography, topography, fluctuations in solar radiation, and volcanism. Feedback loops are numerous: a region s climate determines the types of vegetation found there; however, vegetative cover in turn affects the temperature and rainfall in an area. In addition, climatic conditions can fluctuate in periods as short as a day and as long as millions of years. Before tackling climate change, readers of this book will first receive a thorough grounding in the dynamics of Earth s climate, and how climate interacts with living things and other parts of the Earth system. Readers will then have an opportunity to explore climate change throughout Earth s history before investigating the causes, effects, and current scientific and public policy responses to the phenomenon of global warming. Simply put, climate refers to the average weather occurring within a given geographic location over a long period of time. A location s climate is made up of the standard weather conditions occurring in different seasons, the variability of weather at that location across different periods of time, and the frequency of special atmospheric phenomena, such as tropical cyclones (hurricanes) and tornadoes. More specifically, climate refers to all the elements that cause changes in the atmosphere, such as solar radiation, humidity, cloud cover, and wind and ocean currents. Such a discussion would not be complete without an exploration into how Earth s hydrosphere (the watery regions of the planet), lithosphere (the crust and uppermost portion of the mantle), and biosphere (the region populated by living things) interact with the atmosphere xi

9 7 Climate and Climate Change 7 and with one another. Humans and their activities also affect Earth s climate. The ultimate driver of climate is the Sun, Earth s local star that emits all types of radiation. Some of this radiation reaches Earth s atmosphere and surface. The climate of a particular location on Earth s surface is primarily determined by the amount of solar radiation it receives. Heating is maximized when incoming solar radiation streams at a 90 angle toward Earth s surface. The radiation angle, and thus the amount of radiation, varies with a location s latitude, the seasons, and the time of day. In general, temperature rises when the atmosphere absorbs solar radiation emitted by Earth s surface. Many factors affect how the energy from incoming solar radiation is distributed throughout a region. Cloud cover can scatter radiation before it is absorbed. The amount of water vapour and other gases in the atmosphere influence how much radiation is absorbed. Surface conditions also play a role. For example, snow cover and ice cover reflect a large portion of solar radiation, while surface water absorbs much more. As a result, energy stored in bodies of water can subsequently heat the atmosphere above. At any given time of day, half of the planet is bathed in sunlight, so the Earth system absorbs solar radiation constantly. However, the temperature of the atmosphere remains relatively stable, because Earth also emits heat, or thermal radiation, back into space. The difference between absorbed and emitted radiation at any given point on Earth s surface is the location s radiation budget. The radiation budget is the main factor in a location s total energy budget. Other components of a location s total energy budget include the quantity of energy stored and the quantity transferred in and out by wind and ocean currents. For more than 2,000 years, since the classical Greek period, people have been looking for ways to classify Earth s xii

10 7 Introduction 7 climates. Since then, more than 100 climate classifications have been developed. All can be sorted into either genetic or empirical classification systems. Genetic systems classify climates by their contributing factors, such as energy budgets, wind patterns, or geographical factors. Scientists find genetic schemes appealing because they account for causal factors (such as the movements of air masses, solar radiation, the influence of topography, etc.). They are, however, more challenging to use, because they rely on a complex interpretation of climate observations and often yield results that conflict with the more commonly used empirical classifications. Empirical schemes rely exclusively on observed weather and environmental data and can be based on one or more factors, such as temperature, precipitation, and humidity. Many popular empirical systems have classified regions according to their dominant vegetation type. One of the most well-known climate classifications is an empirical system first published in 1900 by German meteorologist and climatologist Wladimir Köppen. Köppen devised formulas that could describe newly mapped zones of vegetation, using temperature as the primary defining criterion. The Köppen system has been criticized for failing to acknowledge several factors, such as sunshine, wind, periodic droughts or other extreme events, and environmental change. Still, it remains a widely used means of classifying Earth s climates, partly because newer systems are more complex and difficult to work with. As long as there has been life on Earth, living things and climate have influenced one another. Plants, animals, and other life-forms exchange energy and matter with the atmosphere. Before the evolution of life, the atmosphere was believed to have been mainly made up of carbon dioxide and water vapour. Both of these gases are known as greenhouse gases, because they are relatively transparent to incoming shortwave radiation, and xiii

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13 7 Climate and Climate Change 7 more opaque to long-wave radiation (most of which is expressed as heat) emitted from Earth. Four billion years ago, at the start of the Archean Eon (the earlier of the two formal divisions of Precambrian time), the Sun produced only 25 percent as much energy as it does today. However, scientists maintain that large concentrations of greenhouse gases in the atmosphere slowed the emission of long-wave radiation enough to make Earth s temperature similar to that of today. By metabolizing carbon dioxide, early forms of bacteria and other, more primitive organisms gradually changed the composition of Earth s atmosphere. Over time, oxygen levels increased, and carbon dioxide levels fell. Today, carbon dioxide makes up about 0.04 percent of all atmospheric gases a huge reduction. In addition to affecting Earth s radiation budget, the biosphere influences wind, transpiration and evaporation, nighttime temperatures, and other factors that affect climate. Compared to trillions of bacteria found in Earth s biosphere, humans have little influence on the atmosphere through their own metabolic processes. However, people have a greater influence on Earth s atmosphere through their economic and cultural activities. Further, people release carbon into the atmosphere when they burn fossil fuels, such as oil, coal, natural gas, or biomass (trees or grasses). Increasing the carbon concentration in the atmosphere increases the opacity of Earth s atmosphere to heat, and thus smaller amounts are released into space. In addition, people can affect Earth s climate by changing Earth s surface. The degree to which the Sun s energy heats the atmosphere depends, in part, on the reflectivity known as albedo of Earth s surface. Clearing a forest or grassland for agriculture or building construction, for example increases the location s albedo and more energy is reflected back into space than would xvi