A BRIEF HISTORY OF ENERGY Coal

Energy and human history go hand in hand. For most of the time that humans have been on earth, energy was used at a very low level, mostly by burning wood for cooking and warmth. This is still the case for large areas of the planet, espe­cially in much of Africa and parts of Asia and South America. As human popu­lations grew, forests were decimated to obtain fuel, resulting in the collapse of several societies (1). Coal was discovered in England in the thirteenth century and began to be used extensively beginning in the 1500s. Between 1570 and 1603, during the reign of Elizabeth I, coal became the main source of fuel for England (2). This was, not coincidentally, also during the time of the Little Ice Age, when there was a great need for fuel to keep warm.

Coal transformed England, for better and for worse. The development of the coal-based steam engine by Thomas Newcomen in 1712, with further criti­cal developments by James Watt and Matthew Boulton, led to the Industrial Revolution beginning in about 1780. Coal built England into the world’s most powerful country during the nineteenth century. At the same time, it brought about unbelievable pollution, which drastically shortened lives, and it led to child slave labor in factories and mines.

Coal had been discovered even earlier in China and was being used for iron production in the eleventh century (2). Coal was discovered in Appalachia in the United States in the mid-eighteenth century and quickly became its most abun­dant source of energy. This led to the industrial development of the United States, the building of canals to transport coal, and the construction of railroads to con­nect the far reaches of the country. Wherever large sources of coal were found, societies were transformed.

Coal was fine for running steam engines and cooking or keeping warm, but what people wanted desperately was a better source of light for their homes and businesses. Sperm whale oil had illuminated lamps for hundreds of years, but the

whale populations were being decimated and whale oil was expensive; animal and vegetable fats were a poor second choice because they did not burn brightly and cleanly. “Town gas” could be derived from coal, but it was too expensive for gen­eral use. In 1854 a group of investors hired Yale professor Benjamin Silliman, Jr., to study the properties of “rock oil” that seeped out of the ground in Pennsylvania. His studies proved that “rock oil” would make a good source of light (3). The question was whether there was a sufficient quantity readily available.

It is not just some pundits and politicians who disagree with the theory that anthropogenic greenhouse gases are causing global warming. Some prominent scientists have also raised questions. One of the foremost is S. Fred Singer, who is most famous in the popular press for his (and co-author Dennis T. Avery’s) 2008 New York Times best seller Unstoppable Global Warming: Every 1,500 Years (16). Singer developed weather instruments for satellites, he was the first director of the National Weather Bureau’s Satellite Service Center, and he was a professor of environmental sciences at the University of Virginia. In 1990 he started a non­profit advocacy research institute, the Science & Environmental Policy Project, which identifies global warming as one of its main issues. It claims that “com­puter models forecast rapidly rising global temperatures, while data from weather satellites and balloon instruments show only slight warming.” He also began the Nongovernmental International Panel on Climate Control to rebut the conclu­sions of the IPCC reports (17). The criticisms of global warming by Fred Singer represent most of the arguments made by scientists who believe the evidence does not support the theory that man-made greenhouse gases cause global warming. Let’s look at what he says about the science.

First, he argues that climate on earth has undergone very large changes over geological time when humans weren’t around, which is clearly true. Much of ancient climate was driven by a very different arrangement of continents on earth.

About 225 million years ago (mya) the landmasses on earth were united in the supercontinent Pangaea, which began breaking up into two smaller superconti­nents—Laurasia and Gondwanaland. Laurasia consisted of what would become North America, Europe, and Asia; the southern supercontinent Gondwanaland consisted of what would eventually become the southern continents of South America, Africa, Australia, Antarctica, New Zealand, Madagascar, and India. The forces of plate tectonics began to separate Gondwanaland and move the continen­tal pieces about 170 mya. Eventually, Antarctica-Australia, Africa, Madagascar, and India separated from one another, creating the Indian Ocean. A little later, South America separated from Africa and created the South Atlantic Ocean. A seminal event for earth’s modern climate occurred about 30 to 40 mya, when Antarctica separated from Australia and migrated to the South Pole, breaking the Andean link with South America. Another major event was the rise of the Isthmus of Panama between North and South America about 3 mya. This discon­nected the Atlantic and Pacific Oceans and led to the Atlantic Ocean currents that take warm water from the Gulf of Mexico to the Arctic. The altered atmospheric circulation and precipitation patterns in the far north began modern climate pat­terns, and glaciers developed in Antarctica (18).

Two million years ago, a period of alternating Ice Ages and interglacial periods began, caused by “cycles in the earth’s relation to the sun,” according to Singer and Avery. They claim that weather patterns have undergone alterations on a roughly

1.500- year cycle over the last million years. This is based primarily on a paper in Science by Gerard Bond (19) that measured debris dropped from glacial ice into the north Atlantic seabed over the last 12,000 years and compared the variations with fluctuations in solar output. Additional evidence of cycles was obtained from Greenland ice cores analyzed by Dansgaard and Oeschger (20). The ice cores show the major ice age and interglacial climate swings but also show an approximately

2.500- year temperature cycle on top of the major swings. This smaller cycle was later changed to be about 1,500 years (plus or minus 500 years), so that is the basis of their book’s title and their principal rationale for saying that warming from greenhouse gases is irrelevant because the earth naturally undergoes fluctuations on an approximately 1,500-year cycle.

So what could cause a 1,500-year cycle? Singer and Avery try to explain it by the effect of solar activity on extragalactic cosmic rays. When solar activity is weak, more cosmic rays are able to bombard the atmosphere, ionizing air molecules and creating cloud nuclei, which would cool the earth. When the sun is more active, the extra ultraviolet rays (UV) create more ozone, which absorbs more near UV from the sun, warming the atmosphere. One problem with this rather complex theory is that there is no 1,500-year solar cycle. Surprisingly, they ignore the most prominent change in solar activity—namely the 11-year sunspot cycle— which can be readily measured and does affect temperature slightly. The majority of Singer and Avery’s book does not focus on the supposed 1,500-year cycle over the last million years but instead focuses on the last thousand or so years, specifi­cally on the Medieval Warm Period from 900 to 1300 c. e. and a two-stage Little Ice Age from 1300 to 1850. If there really is a 1,500-year cycle, then there should be another warming period beginning in about the year 2400, but we should still be in a cold phase now. But, of course, they give a 500-year fudge factor, so maybe we actually are in a new warming cycle based on their theory—or not. And, impor­tantly, measurements of solar output should be predictive of the climate. Thus, their theory can be tested, and later we will look at evidence as to whether it explains the current state of global temperatures.

Singer and Avery argue that greenhouse gases are not the cause of global warm­ing. They say that the only evidence for greenhouse gas warming is “(1) the fact that the Earth is warming, (2) a theory that doesn’t explain the warming of the past 150 years very well, and (3) some unverified computer models" They go on to give a list of things the greenhouse gas theory supposedly does not explain:

• CO2 changes do not account for the highly variable climate in the last

2.0 years.

• Greenhouse gas theory does not explain recent temperature changes in the twentieth century.

• CO2 increases have not led to planetary overheating.

• The poles should warm the most, but they do not.

• We should discount the “official” temperatures because of urban heat islands.

• The earth’s surface has warmed more than the lower atmosphere up to

30.0 feet, yet the theory says the lower atmosphere should warm first.

• CO2 has been a lagging indicator of temperature by 400 to 800 years for the past 250,000 years.

• Greenhouse gas warming should increase water vapor, but there is no evidence that it is increasing.

Another prominent scientist who is skeptical that CO2 is causing global warm­ing is Richard Lindzen, a prominent professor of meteorology at the Massachusetts Institute of Technology. He proposes that the earth’s temperature is self-regulating through an effect he calls the “iris” effect, essentially an opening in the high cirrus clouds that lets the heat out. According to his theory, when surface temperatures rise, moist air rises in the tropics, but more of it rains out than at lower tempera­tures so there is less moisture to form the ice crystals that make the high cirrus clouds. In effect, he postulates a thermostat mechanism that stabilizes temperature by tropical convection of heat high into the atmosphere, where it is radiated away. He also says that cloud formation is little understood and as oceans warm, more clouds would form, which would reflect more of the incoming solar radiation away (21, 22). While it is certainly true that clouds are not modeled very well, that does not mean that the earth is not warming. And if his theory were really true, then it should have applied in the past to prevent global warming from other mechanisms. So a good test of his theory is whether, in fact, the earth is warming or not.

Even scientists who are convinced that greenhouse gases cause current global warming do not deny that ice ages and interglacial periods have happened

repeatedly in the past and recognize that human activity had nothing to do with them. The main point at issue is whether climate changes over the last 50 years or so are caused by anthropogenic greenhouse gases resulting from burning fossil fuels and from deforestation. Singer and Avery and other global warming skeptics say that we are just having normal climate change that occurs periodically and cyclically, while most scientists say that natural factors cannot explain the recent changes.

Edwin L. (Colonel) Drake, hired by the Pennsylvania Rock Oil Company that was formed by the original investors, found the answer. He was hired to adapt the methods of salt drilling, invented by the Chinese, to drill for oil. On August 27, 1859—just when the investors’ money was completely gone and the order had been given to halt drilling—barrels of oil were pumped from the well, giv­ing new life and money to the venture. Finally, in 1861, “drillers struck the first flowing well, which gushed at the astonishing rate of three thousand barrels per day. When the oil from that well shot into the air, something ignited the escaping gases, setting off a great explosion and creating a wall of fire that killed nineteen people and blazed on for three days” (3).1

The oil was refined into kerosene for lamps, and natural gas that came out of wells with the oil was also used for lighting. These two discoveries transformed the way of life. People could now afford to have better lighting long after dark to read and work, and street lamps lit up the towns. Of course, lighting was just the beginning of the uses for oil. With the development of the internal combustion engine and automobiles in the late nineteenth and early twentieth centuries, the race was on for finding new sources of oil, and the rest is history. Finally, King Coal had met its match.

Thomas Alva Edison, the brilliant American inventor, wanted to find an alter­native to kerosene and natural gas for illumination. He was well aware of the fundamental theoretical discoveries in electricity and magnetism made by James Clerk Maxwell in the middle of the nineteenth century, so Edison began working on electric illumination in 1877; within two years he had developed the incandes­cent light bulb. Because he was a businessman as well as an inventor, he wanted to commercialize the light bulb; in the process, he developed the electrical genera­tion industry. “In 1882, standing in the office of his banker, J. P. Morgan, Edison threw a switch, starting the generating plant and opening the door not only on a new industry but on an innovation that would transform the world” (3). Coal then became the primary source of energy for producing electricity.

In the twentieth century, electricity was used for far more than lighting, with the development of electric motors and all the modern appliances and electronics that people in developed countries depend on. As recognition of its importance to human societies, in 2003 the National Academy of Engineering named electrifica­tion as the most important engineering accomplishment of the twentieth century (4). But this flexible and powerful form of energy depended greatly on coal for its production, ensuring that King Coal was not going away anytime soon.

This brief sketch of energy development is fundamentally a story about the dis­covery and use of ever more concentrated and portable forms of energy. The energy density of fuel is the quantity of fuel used to produce a given amount of energy, such as a kilowatt-hour (kWh) of electricity.2 Burning 1 kg (2.2 lb.) of firewood generates 1 kWh, 1 kg of hard coal generates 3 kWh, 1 kg of crude oil generates 4 kWh, and 1 kg of natural gas generates 5 kWh of electricity (5, 6). It is much easier to transport and store coal—with three times the energy content.

The other important part of the story is that all of these sources of energy are ulti­mately solar energy because wood, coal, oil, and natural gas obtained their original energy from the process of photosynthesis, converting the energy of the sun into hydrocarbons. Coal and oil come from remarkably lush plants that covered large parts of the earth in the Carboniferous (coal-forming) period, roughly from 360 to 300 million years ago, long before the time of the dinosaurs (7). Carbon dioxide (CO2) concentrations were much higher in the Devonian period prior to the Carboniferous period, and much of that CO2 went into the growth of trees and plants. Because much of the world was lowland swamps during this period, when trees and plants died they were buried under anaerobic conditions that did not allow normal decay processes to recycle the carbon (2). Over millions of years, huge amounts of carbon were buried and then compressed under layers of new rock through geological times, finally becoming coal or oil. As modern society digs or pumps up these stores of carbon and burns increasing amounts of these fuels, we are returning the CO2 to the atmosphere, causing global climate change, as described in Chapter 1.

So, let’s look at some of the evidence. To really understand the science behind climate change, it is necessary to look at actual data in graphical form. This may be intimidating to some readers—even many of the students in my class have trouble following graphs—but I encourage you to study the figures carefully, and I will lead you through them in the figure captions and the text. Much of the evidence cited here is obtained from the 2007 IPCC Fourth Assessment Report, the latest IPCC consensus report of over 2,000 scientists that references over

6.0 peer-reviewed scientific publications, as well as data from the US National Oceanic and Atmospheric Administration/National Climatic Data Center (NOAA/NCDC). A mini-scandal broke out in 2010 when hackers broke into computers of leading climate scientists and published e-mails and documents that purported to show that the scientists were manipulating their data to exaggerate the case for global warming. However, five different investigations exonerated the scientists of misconduct (23).

First, let’s look at the record of temperature and greenhouse gases over hun­dreds of thousands of years. How is that possible? When snowflakes fall, they form layers with air trapped in them. In areas such as Antarctica and Greenland, the snow compresses into ice that contains bubbles of air with the constituents of the atmosphere at the time the snow fell. Each year a new layer of ice forms, with a new record of the atmosphere. Cores taken from ice sheets go back for

125.0 years in Greenland and 800,000 years in Antarctica (10). The gases in the bubbles from the ice cores can be analyzed to get a yearly record of the atmo­spheric composition (18). Temperature can also be inferred from these ice cores by measuring the amount of deuterium, an isotope of hydrogen.3

The graphs in Figure 1.1 showhowthe main greenhouse gases (CO2, methane, and nitrous oxide) and temperature have varied over 650,000 years (24). While a temperature scale is not given, modern temperature is about 6°C higher than the average during ice ages (10). It is worth noting that if there is a 1,500-year cycle in temperature, it is a very small effect compared to the large temperature changes over much longer time periods. The shaded areas are interglacial periods—times when the earth is warm and glaciers have melted. There are several important points to be taken from this figure.

First, the greenhouse gases are all at high relative concentrations during the interglacial periods. Second, the concentration of greenhouse gases and the tem­perature rise much more rapidly at the beginning of interglacial periods than they fall as a prelude to a glacial period. Third, although it is not obvious from the graph because of the time scale, a more detailed analysis shows that the concen­tration of CO2 actually lags the temperature by several hundred years. However, recent evidence indicates that the rise of CO2 led the rise in Northern Hemisphere temperatures and the melting of the ice sheets at the end of the last ice age about

20.0 years ago (25). Fourth, there is no precedent during the entire preceding

650.0 years for the dramatic increases in the greenhouse gases in the present age. The concentration of CO2 in previous interglacial periods was about 280 ppm (parts per million), but currently (July 2013) it is at 397 ppm (26).

Clearly, humans did not cause these changes over hundreds of thousands of years, so what did? These cycles of ice ages and warming periods were triggered by cyclical changes in the earth’s tilt, coupled with changes in the shape of the elliptical orbit (eccentricity) of the earth around the sun (the Milankovitch cycle) (15, 18, 27). The earth is currently tilted at 23.4° relative to the plane of its orbit around the sun but this varies from 22.1° to 24.5° in a 41,000-year cycle. This tilt is the primary cause of the seasons in the Northern and Southern Hemispheres. The tilt also precesses like the wobble of a top in a cycle of 23,000 years. Because of the elliptical orbit of the earth around the sun, the earth is sometimes closer and sometimes further away from the sun, which also affects the seasons. The shape of the ellipse changes from more circular to more elliptical in a 100,000-year cycle. Combinations of these cycles affect how much sun the northern and southern latitudes get, and this determines whether snow builds up and forms ice sheets (ice ages) or melts and glaciers recede (18). Looking back at Figure 1.1, the inter­glacial warm periods occur at roughly 100,000-year intervals, indicating that the principal effect is the change in ellipticity of the earth’s orbit (28). Any 1,500-year cycle is a small blip on these large changes.

But why does CO2 follow the temperature changes? The precise details are not clear, but absorption of CO2 in the oceans is the most prominent factor. The upper layer of the ocean contains a similar amount of CO2 as the atmosphere, about 800 Gt (10). Cold ocean water absorbs more CO2, and warmer ocean water releases CO2. (This effect is exactly like the difference between opening a cold can of soda and a warm can of soda. The warm soda can will likely overflow when the can is opened because of the rapid release of CO2, while the cold soda does not release much CO2 and does not overflow.) This results in a positive feedback mechanism whereby warming begins by greater solar exposure due to changes in the earth’s orbit, releasing CO2 from the oceans, which causes more warming, which releases more CO2 in a positive feedback loop. It is entirely expected that there would be a lag of several hundred years because it takes a long time for the vast oceans to warm up and begin releasing more CO2 . But the melting at the end of the last ice age was preceded by an increase in CO2 that helped to warm the Northern Hemisphere and melt the ice sheets, so we cannot take comfort in thinking that rising CO2 has no effect on warming.

Another positive feedback is related to the reflection of sunlight from ice sheets, known as albedo. As ice sheets over continents melt, less sunlight is reflected by ice and more sunlight is absorbed by exposed soil, rocks, and vegetation, which causes more warming. These changes in albedo and the release of CO2 from oceans are the main reasons that the warming periods are much faster than the cooling periods, though still taking hundreds to thousands of years. The most striking thing about Figure 1.1 is the very rapid rise in the concentrations of greenhouse gases in the modern era, which is unprecedented in historical times.

Our story jumps back to the sixteenth century for an entirely new kind of energy that yet again transformed the world. In the Bohemian region of the present-day Czech Republic, near the border with Germany, silver was discovered in a for­est surrounded by mountains known as the Krusne Hory (Cruel Mountains) because of harsh winter storms. As the miners dug for silver, their picks were often gummed up with a black, tarry substance called pitchblende, which made for hard mining and was discarded as waste (8). Nearly a century later a German chemist, Martin Klaproth, began experimenting with the pitchblende and dis­covered that if it was heated, it produced a “strange type of half-metal” that was a new element and that made vivid dyes when added to glass. He named this new element uranium in honor of the planet Uranus, which had just been discovered by his countryman, Frederick William Herschel (8, 9).

There things remained until the serendipitous discovery by Henri Becquerel in 1896 of natural radioactivity from a uranium salt. Marie and Pierre Curie thought there might be other radioactive elements associated with uranium, so they asked for pitchblende from the mines at St. Joachimstal in the Cruel Mountains and began to analyze it. In an extremely laborious process known as fractional crystallization, they systematically purified sub-fractions that had radioactivity and eventually isolated about one-fifth of a gram of a new radioactive element, radium, from a ton of pitchblende. The race was on to discover a number of radio­active elements that were hitherto unknown.

In the beginning of the twentieth century, giants in the world of physics, such as Niels Bohr, Albert Einstein, Ernest Rutherford, Enrico Fermi, Erwin Schroedinger, Max Planck, Werner Heisenberg, and James Chadwick, developed a detailed under­standing of the atom based on an entirely new kind of physics known as quan­tum mechanics. This fascinating story is told in great detail by Richard Rhodes in his book The Making of the Atomic Bomb (10) and is discussed later in this book (Chapter 6). Out of this intellectual ferment came the theory of atomic structure and nuclear decay that led to the development of the first nuclear reactor in Chicago in December 1942, and later the development of the atomic bomb. Uranium and plutonium took a central role in this quest for understanding the atomic nucleus and the process of fission, or splitting the nucleus. For now, the essential point is that it became possible to use an entirely different source of energy to make electricity.

Uranium differs in two fundamental ways from the other carbon-based sources of energy that humans had used up to this point: it did not derive from the sun but rather was created in the cataclysmic stellar explosions known as supernovae, and it has a far greater energy density than any other source of energy known to mankind.3 In contrast to the energy density of 3-4 kWh electrical per kilogram for coal and oil, one kilogram of uranium has an energy density of50,000 kWh electrical (6). This is the essential property that makes nuclear reactors such efficient sources of electric­ity. Fundamentally, a nuclear reactor functions in the same way as a coal-fired plant, but it uses fission instead of burning coal to produce steam, which turns a turbine hooked to a generator to make electricity. And, of course, it does not produce CO2 in the process of producing electricity. How it works will be told in detail in Chapter 5.

These energy sources—coal, petroleum, natural gas and nuclear—provide the bulk of the energy that the world consumes. The main additional sources of energy, with one exception, are also ultimately derived from the sun. These include direct solar conversion to electricity or heat, wind (which is dependent on solar heating), biomass (plants grown to provide either fuel stock or ethanol), and hydropower (which comes from rain that comes from evaporation of water in the oceans). The only other non-solar form of energy is geothermal, which is depen­dent on the heating of the core of the earth by nuclear reactions. So, ultimately, all of our energy comes from the sun or from the atom! But, since I am a physicist and have to be picky about these things, the sun’s energy comes from the fusion of atoms (not fission), so really all of our energy comes from the atom!

Now let’s look at a different time scale to see how things have changed over the last

10,0 years. This 10,000-year period is known as the Holocene; the climate was generally stable, with little fluctuation in temperature, and it spawned the dawn of civilization and agriculture. It includes the time known as the Medieval Optimum or Medieval Warm Period (800 to 1300 c. e.), when the Vikings settled Greenland, but also the Little Ice Age (1300 to 1800 c. e.)4 in Europe (27). Both of these events were probably caused at least partly by changes in solar intensity. A paucity of sunspots reflecting reduced solar output—known as the Maunder Minimum— occurred between 1650 and 1715 during the coldest part of the Little Ice Age (18). There were only small changes in concentrations of greenhouse gases in the last

10,0 years until roughly the last 100 years, when all of them have increased very rapidly (Figure 1.2). The inset shows changes since the industrial period began in 1750. Temperature and greenhouse gas measurements are also more precise dur­ing this latter period.

Carbon dioxide is the greenhouse gas that is of most concern, since it is in the highest concentration and is increasing most rapidly by burning fossil fuels and deforestation, so we will focus our attention on it now. While Figure 1.2 shows a dramatic increase in CO2 (top graph), methane (middle graph), and nitrous oxide (bottom graph) in the last 50 years, it does not give any indication of the global average temperatures. It does show a scale that indicates radiative forcing. This is a “measure of the influence that a factor has in altering the balance of incoming and outgoing energy in the earth-atmosphere system and is an index of the impor­tance of the factor as a potential climate change mechanism. Positive forcing tends to warm the atmosphere while negative forcing tends to cool it.”(1) Radiative forc­ing is given in units of energy rate (power) per area (watts per square meter, or W/ m2) at the tropopause.5 (See Appendix A for more information on radiative forc­ing.) What this means is that CO2 is adding a positive radiative forcing (1.66 W/ m2) to the atmosphere that should contribute to global warming. So does it, or are the skeptics right when they say that global temperature is not actually increasing?

I should warn you that this section is filled with numbers and statistics. If you want the short version, what it basically says is that we use too much fossil fuels
producing energy, and it is going to get worse. As a result, we produce too much CO2, with serious consequences for global warming. Renewable energy sources are not sufficient to make a big dent in our use of fossil fuels, either now or in the future. Now for the numbers (or skip to the next chapter, but really you shouldn’t!).

The total yearly demand for energy in the United States is currently about 95 qua­drillion BTUs (quads),4 according to the US Energy Information Administration (EIA). The vast majority (82%) of this energy comes from three different fossil fuels: petroleum, natural gas, and coal. Nuclear reactors contribute about 8.5%, and renewable energy contributes 9.3% (Figure 2.1) (12). The renewable energy component is a bit misleading, since most people think of renewable energy as wind and solar. Actually, the renewable energy component is derived from several different sources, with biomass (mostly wood and corn-based ethanol) being the largest at 4.6%, followed by hydroelectric (2.8%), wind (1.4%), solar (0.25%), and geothermal (0.24%).

The other big factor to consider is how we use the energy. These various sources of energy are used for transportation, to run industries, to heat and cool residences and commercial buildings, and to generate electricity (Figure 2.2). The largest use of petroleum is for transportation, though about one-quarter is used for industrial processes and 5% for residential and commercial consumption. Only about 1% of petroleum is used for electric power production. Natural gas is used in roughly equal proportions for electric power production, industrial processes, and resi — dential/commercial heating with about 3% used for transportation. Over 90% of coal is used for electric power with about 8% for industrial processes. Nuclear

Nuclear,

8.5%

Renewable Energy, 9.3%

Petroleum,

36.5%

Coal, 18.3%

Natural gas,
27.3%

Figure 2.1 Sources of energy for the United States in 2012. The total amount of energy was about 100 quads, so each percentage is also roughly the amount in quads. source: Data from EIA, Monthly Energy Review May 2013.

reactors are used entirely for electric power generation, while renewable energy is divided among all four uses, with half going to electric power (13).

What insights can we gain from this information about energy sources and uses? One important point is that petroleum accounts for about 36% of US energy and 45% of that is imported, so about 15% of all US energy is imported. This is a dramatic change from just a few years ago, when over 60% of petroleum was imported (14). The decrease in imports is because of both increased production and decreased use of petroleum. Another major point is that 84% of our energy comes from fossil fuels, and all fossil fuels produce CO2. This is an inevitable con­sequence of the fact that, no matter how “clean” or efficient the process, burning any source of hydrocarbon ultimately produces CO2 and water. Natural gas burns more cleanly than petroleum or coal, but it still produces about half as much CO2 as that produced by burning coal because of the difference in energy den­sity; burning petroleum produces an intermediate amount of CO2 for the same amount of energy produced.5 Thus, the idea of “clean” fossil fuels is an oxymoron because you can’t get away from the production of CO2, which will produce global climate change, as described in Chapter 1.

Another obvious but important point is that different sources are important in different applications. Most petroleum products are used for transportation, so reducing the use of petroleum will require much greater efficiency in automobiles. Petroleum is also the only source of energy that is largely imported rather than produced in the United States, which has major geopolitical consequences, so there is more than one good reason to reduce dependence on petroleum. Coal, on the other hand, is used almost exclusively for electric power production, so its use can be reduced by conservation and by producing electricity with nuclear power plants and renewable energy sources. These two factors are not unrelated, though.

Increasing the efficiency of automobiles is expected to be done in part by pro­ducing electric cars that can be plugged into the electrical grid. But where does the power come from to charge the batteries of the electric cars? If it comes from coal, the problem is equally bad or worse, not better. According to a US Department of Energy study, both all-electric vehicles and plug-in hybrids generate more CO2 than a regular hybrid in the Midwest and eastern United States because of the greater dependence on coal for electricity to power the cars (15). Furthermore, if a large fraction of the US automobile fleet were electric cars, it would impose a very large additional electrical energy demand, which would require many more power plants.

Now let’s look more closely at where we get electrical power, since that is the focus of this book. More than 40% of the total energy usage in the United States is devoted to the production of electricity, with the majority coming from fos­sil fuels. Coal provides 41% of the energy to produce that electricity, natural gas provides 24%, and petroleum provides 1%, so 66% of our electricity generation comes from fossil fuels that produce CO2 (Figure 2.3). Nuclear reactors provide 21% of our electric power, and renewable energy provides 12%. Of that 12%, 57% comes from hydropower, with wind and solar contributing only 29% and 0.9%, respectively. Thus, as of the end of 2012, wind provides 3.6% and solar provides 0.11% of the electric power in the United States (12). These renewable energy sources have a very long way to go to make up a significant part of the total energy portfolio for the United States.

What can we expect for the future? Are wind and solar power going to be able to make a big dent in the amount of coal that is used to produce electricity? The

EIA produces a report every year that assesses current energy usage and proj­ects usage and sources into the future. The latest report (Annual Energy Outlook 2013) makes projections into 2040 (14). According to their reference report, which takes into account current laws but does not consider future policies that may change, the total energy consumption will increase 10% from 98 quads in 2011 to 108 quads by 2040. Of that total energy, 78% will be provided by fossil fuels from coal, oil, and natural gas, which represents an actual increase in fossil fuel usage of about 5 quads. Most of this increase comes from increased natural gas produc­tion. Electricity usage goes up even faster than total energy usage, increasing 31% by 2040. You might think that energy conservation and efficiency will prevent this from happening, but these projections already include a 46% reduction in energy intensity6 compared to 2011. Even with substantial increases in renewable energy, going from 10% to 14% of electrical generation for the United States, the use of coal still goes up about 5% from 2011 to 2040. Still, there is some good news. Because of the increased use of natural gas and greater efficiency, energy-related CO2 emissions are expected to be 5% less in 2040 than they were in 2005.

Many states require a large increase in renewable energy for electricity gen­eration through what are known as renewable portfolio standards. My state of Colorado mandates that 30% of electricity must be generated by renewable sources by 2020; California mandates that 33% of its electricity be generated by renewable sources by 2020. Making a law and actually doing it are two very dif­ferent things, though. The difficulties of meeting these targets will be discussed in Chapter 4.

Before we evaluate that, let’s look at the modern measurements of CO 2 in the atmosphere. In the 1950s, David Keeling developed techniques to accurately mea­sure the concentration of CO2 in the atmosphere near his home in California and established a baseline concentration of 310 ppm. Later he established a laboratory on top of Mauna Loa, a volcano in Hawaii, and began taking daily measurements of CO2. One dramatic discovery was that the earth breathed in CO2 during the summer as leaves grew and consumed CO2 during the process of photosynthesis. During the fall and winter the leaves fell from the trees and released CO2 as they decayed. He measured semi-annual variations in the atmospheric concentration of CO2 reflecting the breathing earth, causing the zig-zag in Figure 1.3. Of more profound significance, he showed that the concentration of CO. in the atmo­sphere was steadily rising and not in a linear fashion but exponentially (29, 30). The concentration of atmospheric CO2 over time became known as the Keeling Curve (Figure 1.3).

One of the people profoundly affected by the Keeling Curve was Al Gore, who first heard about it when he was a student at Harvard from Professor Roger Revelle, Keeling’s scientific mentor. Al Gore subsequently made it famous to a

more general audience in his books Earth in the Balance and An Inconvenient Truth. The Keeling Curve was the prod that stimulated the scientific concern about global warming.

Now let’s look at whether temperatures really are increasing as you would expect from the increase in CO2 shown in the Keeling Curve. In a report on indi­cators of global climate change (31), the US National Oceanic and Atmospheric Administration National Climatic Data Center (NOAA/NCDC) presents data comparing atmospheric CO2 levels with global average temperatures since 1880. I have updated the figure with data through 2012, using historical CO2 data from Etheridge et al. (32) (Figure 1.4). The global temperatures have a lot of variabil­ity, but the trend to increased warming since about 1980 is indisputable, and the trend follows the increase in CO2 quite well. Skeptics such as George Will say that global warming has not occurred over the last decade (since 1998). Presumably he thinks that temperatures will increase every year if there really is global warming.

However, it is not very scientific to just say there appears to be a trend. A series of data can and should be analyzed by a mathematical process called linear regres­sion to determine if there is actually a change that is statistically valid over a cer­tain time range, and the range has to be large enough to avoid too much influence from any particular year. One cannot just cherry pick a particular year and say that there has been no warming since then, which is what George Will does. There are factors that can strongly affect the weather and temperatures in any individual

year. Volcanic eruptions eject aerosols into the atmosphere that cause cooling for a few years, depending on the size of the volcano, and the El Nino/Southern Oscillation (ENSO) causes warming in years of a strong El Nino. In contrast, years of a strong La Nina lead to global cooling.

A more detailed look at the temperature and CO2 records since 1980 will make these ideas clear. I have plotted the temperature anomalies (change in tempera­ture from the 20th century average) and the atmospheric concentration of CO2 in Figure 1.5. This graph also shows times of major ENSO events (El Nino), which cause transient warming, and the El Chichon and Mount Pinatubo volcano erup­tions in 1982 and 1991, which led to several years of cooling due to aerosols thrown into the atmosphere. 1998 was a year of a particularly strong ENSO, which is why it was an abnormally warm year. In scientific parlance, it is an outlier year. It is clear that the supposed lack of warming since 1998 is wrong, since it was slightly warmer in both 2005 and 2010. While the last decade has been the hottest ever, the five-year running average temperature has essentially been flat, probably due to natural climate variations from El Nino and La Nina events and aerosols (33) and an unusual warming of the deep ocean, which has absorbed much of the excess heat in the last decade (34).

The line in the graph is the linear regression line for temperature anomalies (the equation is in the upper right of Figure 1.5), which contains two interesting pieces of information. One is that the slope of the line gives the annual increase in temperature over this entire time period, which is 0.0153°C per year, or 0.153°C

(0.28°F) per decade, as it is usually stated. The other is the statistical correlation (given by the value of R2 = 0.79), which indicates a relatively strong correlation between the actual temperatures and an annual linear increase shown by the slope of the line. The closer the value of R2 is to 1, the more likely a straight line best describes the data.

The slope of the line can be compared to slopes of similar temperature changes over longer time periods to see if the rate of increase is changing. According to the IPCC 2007 (24), the slope over a 150-year period (ending in 2005) was 0.045°C per decade, over 100 years was 0.074°C per decade, and over 50 years was 0.128°C per decade. This means that the rate of increase in average annual temperature has been going up more in recent decades than previously (remember it has been going up by 0.153°C per decade since 1980). In other words, the actual global temperature is increasing more than linearly over the last hundred years (for the mathematically inclined, it can be best fit by a second order polynomial, not a straight line).

The annual atmospheric CO2 concentration is also plotted in Figure 1.5, which shows that CO2 is increasing similarly to temperature. In fact, CO2 is also going up more rapidly than linearly. Considering the data in Figures 1.4 and 1.5 together, it is hard not to conclude that rising CO2 levels are leading to higher global tem­peratures, especially since physics says that higher CO2 should cause warmer temperatures.

A simple but profound question to answer about the connection between CO2 and global warming is how much warming would be expected from a rapid dou­bling of CO2. The value is known as the climate sensitivity, and it is critical for evaluating what to expect as we continue to pour more CO2 into the atmosphere. Probably the best value for the climate sensitivity comes from paleoclimate stud­ies done by James Hansen. He compared the conditions during the last ice age with the recent Holocene period averaged over a millennium when the earth was in energy balance. The climate forcing from atmospheric CO2 and reflection from ice (albedo) determine the temperature difference between the two eras. This results in a calculation of 0.75°C for each W/m2 of climate forcing. Doubling CO2 from the long-term interglacial average of 280 ppm leads to a forcing of 4 W/m2, so that would mean a temperature rise of 3°C for doubled CO2. Hansen used this value to calculate the paleoclimate temperature, as in Figure 1.1, and could accu­rately model a 400,000-year range of temperatures based solely on atmospheric greenhouse gases and albedo from ice sheets. Models also suggest that climate sensitivity is 3°C (21, 35).

But, you say, how about Singer’s argument that it is actually solar irradiance, not CO2, that is causing any global warming that might be occurring and that leads to a roughly 1,500-year cycle of warming? Can the observed global warm­ing be explained by solar irradiance? The largest change in solar irradiance in the short run is the 11-year solar cycle. Satellite measurements of solar irra­diance at the top of the atmosphere (Figure 1.6) show that there is a regular 11-year (actually 10-12 year) cycle of changes in solar irradiance but no con­stant increase that would explain the continued warming of the earth (31).6 The average temperature, which jitters up and down from chaotic weather, shows lit­tle effect from the changes in solar output. In fact, the solar output was decreas­ing from 2001 to 2010, while the earth experienced the hottest decade in the last 100,000 years.

The IPCC also concludes that any radiative forcing from solar irradiance is just 0.12 watts per square meter, while the radiative forcing from CO2 is more than ten times greater (1.6 W/m2).7 Furthermore, the IPCC discusses the potential contri­bution of cosmic ray intensity to cloud cover and concludes that “the cosmic ray time series does not appear to correspond to global total cloud cover after 1991 or to global low-level cloud cover after 1994” (24). Thus, Singer’s hypothesis— that any global warming that might occur is from solar irradiance rather than CO2—does not hold up. The IPCC concludes that “most of the observed increase in globally averaged temperatures since the mid-20th century is very likely (>90% chance) due to the observed increase in anthropogenic greenhouse gas concentra — tions.”(1) Each of the four IPCC reports have led to stronger and stronger state­ments about the likelihood that humans are causing the increased global warming as the data keep rolling in to support the statements.

Another point needs to be made about the global temperatures. Singer and other global warming skeptics raise a red herring that temperatures are not accu­rate because of “urban islands” where temperatures are hotter, thus skewing the temperature data. However, this has been taken into account in the land-based temperature records used in the official global temperatures and it makes only a very tiny correction of 0.01° C (36). Also, the “urban island effect” would not affect ocean temperatures, which are increasing very similarly to land temperatures (24).

If global temperatures are actually increasing as demonstrated here, and contrary to what climate change skeptics such as George Will and Fred Singer assert, then there should be other symptoms, such as melting glaciers and rising oceans. In fact, this is certainly the case. Sea levels have been rising slowly since 1880 and

much more rapidly since about 1940 (Figure 1.7). The rate of rise has been about 1.7 mm per year over the last 100 years, but, as shown in the insert, has been approximately 3.5 mm per year (about 1.4 inches per decade) from 1993 through 2009 (31). The cause of more than half of this rise in sea level is due to thermal expansion of the ocean from the warmer temperatures. The rest is from melting of glaciers and ice caps (about 30%) and Greenland and Antarctic ice sheets (about 15%) (24).

Greenland ice has been shrinking at 50-100 Gt/yr 8 from 1963 to 1993 and at even higher rates from 2003 to 2005 (37). A recent analysis of several different methods to measure ice loss shows that Greenland lost ice at the rate of 263 ±30 Gt/yr between 2005 and 2010 (38). Antarctica has a number of ice shelves that have been receding since the late 1980s, mostly in the Antarctic Peninsula and West Antarctica (39). The Antarctic Peninsula has been warming much more rapidly than the rest of Antarctica, but recent analysis of Antarctic temperatures show that West Antarctica has warmed by 0.17 ± 0.06°C per decade between 1957 and 2006, with the peninsula warming by 0.11 ± 0.04°C per decade, and continent-wide warming of 0.12 ± 0.07°C per decade (40). East Antarctica has actually gained ice because of higher precipitation while the Antarctic Peninsula and West Antarctica have lost ice. The net Antarctica ice sheet loss was 81 ± 37 Gt/yr between 2005 and 2010, for a combined Greenland and Antarctica ice sheet loss of 344 ± 48 Gt/yr (38).

Ice sheet dynamics play a critical role in the loss of ice from Greenland and Antarctica. The ice on Greenland is about two miles thick in the center and tapers

off at the edges. As surface ice melts, it forms large lakes on the surface. Sometimes enormous moulins or holes form in the ice where the water disappears to the base of the ice sheet and flows to the sea (41). These rivers of water lubricate the base of the ice and can increase the rate of flow of the ice into the sea but the details are not well understood. Antarctica is covered by a sheet of ice that averages about one and a half miles thick but is two and a half miles thick at its maximum and contains about 10 times as much ice as Greenland. The pressure of this ice sheet forms glaciers, or rivers of ice, that slowly flow to the sea. Floating ice shelves, such as the Ross and the Larsen ice shelves, form where glaciers enter the sea. These ice shelves butt up against the glaciers and retard the flow of glacial ice into the sea. In recent years, enormous sections of the Larsen and Wilkins ice shelves have disintegrated, removing the pressure against the glaciers so they flow more rap­idly into the sea. These ice sheet dynamics in both Greenland and Antarctica can potentially lead to much more rapid ice loss than is considered in the IPCC esti­mations of ice loss (18, 42), which would raise estimates of predicted sea level rise.

Melting of the Arctic ice does not contribute to rising sea levels, since the Arctic ice is floating in the ocean already. But it is an indicator of global warm­ing. According to the National Snow and Ice Data Center, the maximum extent of winter Arctic sea ice occurs in March and has been declining at a rate of 2.6% per decade since 1979 (when satellite measurements began). The summer Arctic sea ice melt season now lasts nearly a month longer than it did in the 1980s. The minimum Arctic sea ice occurs in mid-September, and it has been declining at 13% per decade compared to the average from 1979-2000. The least Arctic sea ice extent since 1979 occurred in September 2012 and was 16% lower than the previ­ous low in 2007 (43). The loss of sea ice has a positive feedback on global warming because ice reflects the sun while the dark ocean absorbs it. So the loss of summer sea ice causes even greater warming due to this albedo effect.

Glaciers have been melting worldwide for most of the last century, as dramati­cally illustrated by Al Gore (44) and as shown in Figure 1.8. Not all glaciers are melting, and a few glaciers are actually increasing due to increased precipitation in some areas, but worldwide the melting trend is clear and accelerating. Not only is this a concern for long-term rise in sea level, but of even greater concern is the fact that water for the major rivers in Asia comes from glaciers in the Himalayas, which are melting as part of the overall glacial decline. About 2 billion people in more than a dozen Asian countries depend on rivers fed from glaciers and snow in the Himalayas and the Tibetan Plateau. The Tibetan Plateau is heating up twice as fast as the global average, leading Chinese scientists to believe that 40% of the glaciers could disappear by 2050 (45).