As the pundits, politicians, and some scientists love to say, the predictions of global warming are based on models that do not accurately reflect the com­plexity of climate systems. However, the predictions of models for yearly global

average surface temperatures have been fairly accurate, within the margin of error, even going back to the First Assessment Report in 1990. Since that time, of course, computer technology has advanced enormously so many more factors can now be taken into consideration, including aerosols, reflection of the sun from snow cover (albedo), and some limited effects from cloud cover, though this is an area that is still developing. So, let’s look at the predictions of models that consider human effects in producing greenhouse gases and models that do not consider these effects but only consider natural effects such as solar irradiance.

The actual results of models show that the observed temperatures since about 1970 cannot be modeled without considering the radiative forcing due to green­house gases (Figure 1.9). The models based solely on natural factors indicate that we should be in a slight cooling trend, but in fact global temperatures have been rising, as clearly demonstrated in this chapter. The observed results fall right in the middle of the error margins of the model predictions that include human effects. This should give substantial confidence that the models are in fact accu­rately considering the most important factors leading to global warming, and that the most important factor is human effects from greenhouse gases.

“Get under your desks. The missiles are coming" “The President has been shot!” “The National Guard has killed four students at Kent State" “The river is burning!” These are my searing teenage and early adult memories. My forma­tive years took place in the 1960s, when society was seemingly coming apart at the seams, with riots over the Vietnam War, riots over racial issues, and the assassinations of President John F. Kennedy, Robert Kennedy, and Martin Luther King, Jr. The Cold War was in full swing and there was great fear that the United States and the (former) Soviet Union would annihilate the world with a nuclear holocaust. In addition to these crises, the environment had become degraded to such an extent that the Cuyahoga River caught fire and the air in major cities was not safe to breathe. In response to this toxic mix of social and environmental ills, many citizens began questioning whether they could trust the government or technology. Fueled by this questioning, a new sense of activism led to (among other things) an environmental movement that helped establish the Environmental Protection Agency (EPA) to clean up our rivers and air.

This was a time when books such as Silent Spring (1), The Population Bomb (2), and The Limits to Growth (3) were proclaiming dire consequences for our planet if we didn’t take our impacts on the planet more seriously. It was also a time when environmental activists became very concerned and vocal about the haz­ards of nuclear weapons and radiation in general. Fears of even a limited nuclear war leading to a “nuclear winter” were prevalent. As nuclear power plants were being proposed, fierce demonstrations took place to try to prevent them from being built and delaying the time line for actually building them to ten or more years. A large segment of society became convinced that virtually any exposure to radiation would cause cancer and that nuclear reactors were a major health hazard. These fears were amplified by books such as Nuclear Madness (4) by Helen Caldicott, one of the fiercest critics of nuclear power.

The hysteria of a nuclear power reactor meltdown was promoted by the movie The China Syndrome. Those worst fears seemed to come true in 1979, when the Three Mile Island nuclear reactor sustained a partial nuclear core meltdown, and then again in 1986, when the reactor at Chernobyl suffered a complete meltdown and spewed massive quantities of radiation into the air. The Three Mile Island accident led to a total shutdown of new nuclear reactors in the United States and the cancellation of many that were being built. The Chernobyl accident further shredded the allure of nuclear power.

Fast forward to the present, and it is clear that the air and water in the United States have been dramatically improved. The EPA has become a powerful force for reducing the degradation of the environment caused by human activities that was done so cavalierly in the 1960s and earlier. However, in the last decade or two, it has become increasingly apparent that our addiction to fossil fuels for transportation and electricity has led to a major environmental problem that threatens to dwarf the earlier concerns—global climate change. The overwhelming consensus of environ­mental scientists is that greenhouse gases, primarily carbon dioxide (CO2) formed as a result of burning fossil fuels and deforestation, are driving climate change in a way that threatens to alter the earth’s sustainability in major ways (5). While the number of people on earth has not reached the dire predictions of books such as The Limits to Growth, relentless population growth has continued to increase the need for energy and other resources, not only in the United States but worldwide. Furthermore, the developing nations, especially India and China, are dramatically increasing their need for energy as they develop into modern societies, as described so eloquently by Tom Friedman in his book Hot, Flat and Crowded (6).

Where does the energy come from that provides for the US and world needs? In the vast majority of cases, it comes from fossil fuels, which produce large amounts of CO2 in the process of generating electricity. In the United States, coal, petro­leum, and natural gas provide about 80% of all energy and 66% of electricity pro­duction. Coal is by far the leader in generating electricity, providing 41% of all electricity in the United States, while natural gas provides 24%. Renewable energy (including hydropower, which is currently by far the largest component of renew­able energy) provides about 12% of electricity, and nuclear power provides 21%. While there is currently a lot of interest in solar and wind for generation of elec­tricity, they have limitations that prevent them from making a large dent in the use of coal and other fossil fuels. By the end of 2012, solar and wind contributed only 3.7% of the electricity generated in the United States. It is clear to me that nuclear power is the only alternative source of clean energy that has the capacity to substantially reduce the use of coal to generate electricity. Because of the fears that were raised in the 1960s and 1970s by environmentalists about the dangers of nuclear power and radiation, the general public is alarmed about increasing the use of nuclear power, and most environmental organizations are opposed to it. The nuclear accident at Fukushima in 2011—the result of a catastrophic earth­quake and tsunami—added fuel to the anti-nuclear fire.

This book has developed out of my concern for the environment, dating back to the 1960s, as well as my 35-year professional career as a radiation biologist. I am a long-time member of the Sierra Club, The Nature Conservancy, the World Wildlife Fund, and the National Wildlife Federation. I have a mountain cabin that is off the grid and relies exclusively on solar power and battery storage for electric­ity generation, and I also have a solar system on my house that is tied into the grid, so I am a proponent of alternative energy. But I am also convinced that, while very important, wind and solar energy cannot be produced in the massive quantities needed to reduce or replace coal as a primary source for generation of electricity, or even keep up with the increasing worldwide demand for electricity.

As a professor at Colorado State University, I have taught undergraduate and graduate courses on radiation and its biological effects. As the environmental con­sequences of burning fossil fuels became increasingly apparent, I began to focus on the issues associated with nuclear power because of its strategic importance in reducing the huge amounts of CO2 released into the atmosphere from burn­ing fossil fuels for electricity production. While there are an increasing number of books both in favor of and opposed to nuclear power, none of them provides a clear explanation of what we know about the biological effects of radiation and how we know it. There are many myths about radiation and some legitimate con­cerns. The goal of this book is to explore these issues with a firm foundation in science. While the creation of this book has its roots in the courses I have taught, it is not intended to be a scientific textbook but rather a book that will help an educated public better understand the issues and myths associated with nuclear power. This book is for you if you are interested in where we get our energy for electricity, how energy production impacts the earth’s environment, and what we can do to meet our future energy needs while reducing CO2 production and limit­ing environmental impacts.

Since the issue of greenhouse gases and global warming in the context of cur­rent energy utilization and projections for the future is essential to the basic mes­sage of the book, I evaluate the scientific knowledge of global warming in the first section. Several graphs clearly demonstrate the evidence for global warming and its relationship to human-caused CO2 production. Then I discuss in detail the sources of our energy and evaluate the pros and cons of coal, petroleum, natu­ral gas, solar, wind, and nuclear power. This section emphasizes the serious con­sequences for global warming of burning fossil fuels but also demonstrates that renewable energy has many limitations and is not sufficient to solve the global warming problem. Thus, the rationale for increasing the use of nuclear power for electricity production to minimize global warming is developed.

The second section is devoted to explaining what radiation actually is (I will try to keep the physics to a minimum, but as my students know, I love to talk about physics so I may get carried away!) and what a “dose” of radiation means. The specific types of radiation will be described in the context of radiation associated with a nuclear reactor. Most people are unaware that by far the greatest human exposure to radiation comes from natural background radiation and diagnostic medical exams. In order to understand the potential consequences of exposure to radiation from nuclear power generation, it is essential to put it in the context of that natural exposure to background radiation in our environment.

What we care about, of course, is what radiation from any source does to our cells and bodies. To understand this, it is first necessary to look at how radiation damages DNA and how cells respond to that damage. It may come as a surprise to many people that our cells have evolved complex and sophisticated molecu­lar methods to repair DNA damage from radiation and other damaging agents. However, under certain conditions, radiation may kill cells or cause mutations. The ability of radiation to kill cells is important in radiation therapy for cancer, while the ability to cause mutations is how radiation can cause cancer.

As it turns out, we know more about the biological effects of radiation and its ability to cause cancer than nearly any other toxic agent. How do we know that? Information on the carcinogenic effects of radiation on humans comes primar­ily from the Japanese survivors of the two atomic bombs dropped during World War II and from humans who have been exposed to substantial doses for medi­cal purposes. Our basic understanding of how radiation causes mutations and genetic damage comes from a vast literature on cellular and molecular studies by radiation biologists. This section is critical to understand the probability of getting cancer from exposure to a particular dose and is essential for understanding the potential hazards associated with nuclear power.

The last section deals with specific issues associated with nuclear power. Mining and milling of uranium ore has traditionally been done in underground or pit mines, but newer in situ leach mining methods greatly reduce the potential expo­sure to radiation and also the environmental damage associated with pit mining. A chapter on uranium will explore the issues of mining and discuss the long-term availability of uranium to power a nuclear renaissance.

The potential for accidents is an important factor in the use of nuclear power— perhaps the largest factor in most people’s minds. I discuss the causes and the envi­ronmental and health consequences of the nuclear accidents at Three Mile Island, Chernobyl, and Fukushima. It will surprise most people that the consequences are much less than is generally presumed—the “wasteland” around Chernobyl has actually turned into an island of biodiversity. The overall safety record of nuclear power turns out to compare very favorably with other sources of energy, especially fossil fuels. As a result of these accidents, better operating procedures and designs of nuclear reactors minimize the potential for future accidents. Even considering the Three Mile Island accident, there has not been a single life lost in 50 years of operation of commercial nuclear reactors in the United States. That certainly can­not be said for coal or natural gas!

The waste from nuclear reactors is of paramount concern to most people, but there is a great deal of misunderstanding about the hazards of long-term nuclear waste storage. It is first necessary to understand exactly what is contained in nuclear waste and how it decays over time—back to the physics! Then I discuss the much-maligned nuclear waste repository planned for Yucca Mountain. It has been deeply mired in politics, but the potential radiation exposure to future popu­lations would actually be minimal. What will surprise many people is that we already safely store military nuclear waste at a deep salt mine near Carlsbad, New Mexico, known as WIPP (Waste Isolation Pilot Plant). And nuclear waste can also be a resource. France recycles their nuclear waste to extract the uranium and plu­tonium so it can be made into new fuel. This greatly reduces the long-term storage problem of nuclear waste. Is this what we should be doing? It is an option that is available if we choose to pursue it.

I am convinced that greater use of nuclear power is essential for minimizing the effects of energy production on global climate change. However, I have tried to address this subject with an open mind and to present the best scientific evidence and analysis that bear on this very important public policy question. I hope that you will read this book with an open mind also, in spite of what may be a bias against nuclear power, and will learn that radiation is not nearly as hazardous or scary as the majority of Americans believe or the popular press paints it. The issue of energy production and its consequences for the earth and all living systems— including ourselves, our children, and their children—is far too important to have an uninformed debate. My hope is that this book will contribute to an informed debate about the difficult options we face. Truly, there is no free lunch, and dif­ficult decisions will have to be made. Better that they be guided by an informed citizenry than one paralyzed by fear.

“The ice caps are melting!” “The coast is flooding!” Let us work now, while there is still time, so that this will not be the reality our grandchildren will face.

REFERENCES

1. Carson R. Silent Spring. Boston: Houghton Mifflin, 1962.

2. Ehrlich PR. The Population Bomb. New York: Ballantine Books, 1968.

3. Meadows DH, Meadows DL, Randers J, Behrens III WW. The Limits to Growth. New York: Universe Books, 1972.

4. Caldicott H. Nuclear Madness-. What You Can Do! Brookline, MA: Autumn Press, 1978 .

5. Alley R, Bernsten T, Bindoff NI, Chen Z, et al. Summary for policymakers. In: Solomon S, Qin D, Manning M, et al. eds. Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Cambridge, United Kingdom and New York, NY: Cambridge University Press, 2007; 1-21.

6. Friedman TL. Hot, Flat, and Crowded. New York: Farrar, Straus and Giroux, 2008.

PART ONE

Global Warming and Energy Production

We can now reconsider the criticisms by Singer and Avery (in italics), which represent other scientific global warming skeptics, who gave a list of things they claim the greenhouse gas theory does not explain.

Year

Observations

Models using only natural forces

Models using both natural and human forces

Figure 1.9 Comparison of observed global (land and sea) temperature with results simulated by models using natural and human radiative forcing. The lower (dark gray) band is the 5-95% range for 19 simulations from 5 climate models using only natural forcing. The upper (light gray) band is the 5-95% range for 58 simulations from 14 climate models using both natural and human radiative forcings. source: Reproduced by permission from Climate Change 2007:The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Figure SPM.4 (Cambridge: Cambridge University Press, 2007).

• CO2 changes do not account for the highly variable climate in the last 2,000 years. This is true, but scientists do not say that greenhouse gases are the only thing that affects climate.

• Greenhousegas theory does not explain recent temperature changes in the twentieth century. Increased production of greenhouse gases as a result of human activity is, in fact, the only way to account for the temperature changes in the last 50 years.

• CO2 increases have not led to planetary overheating. The results presented here clearly show that, in fact, the planet is overheating and the rate of warming is increasing steadily.

• Thepoles should warm the most, but they do not. The northern latitudes, and especially the Arctic, are in fact warming at a more rapid rate than elsewhere on the planet (24). West Antarctica is warming at the same rate as the rest of the earth.

• We should discount the “official” temperatures because of urban heat islands. scientists are well aware of this, and temperature records have been corrected for this phenomenon. Furthermore, ocean temperatures are also increasing.

• The earth’s surface has warmed more than the lower atmosphere up to 30,000feet, yet the theory says the lower atmosphere should warm first. Actually, temperatures measured by balloons (radiosonde) and satellites have increased in the middle troposphere (5,000 to 30,000 feet) very similar to

surface temperatures during 1958-2000 (0.12°C per decade for surface and 0.15°C per decade for mid-troposphere) and at an even higher rate since 1976 (0.17°C per decade in the mid-troposphere) (24, 46).

• CO2 has been a lagging indicator of temperature by 400 to 800yearsfor the last 250,000 years. This may have been true in the past, but as shown here, it is tightly linked to temperature changes over the last 50 years.

This is because we are artificially adding CO2 to the atmosphere at an unprecedented rate from fossil fuel use and destruction of forests.

• Greenhouse gas warming should increase water vapor, but there is no evidence that it is increasing. Water vapor actually has increased over the oceans at a rate of 1.2% per decade from 1988 to 2004 (24).

While there may be scientific quibbles with the finer points of issues related to global warming, the broad picture as presented here is extremely well supported by peer-reviewed scientific publications and is the scientific consensus.

As a final point to this discussion, it should be said that the physics showing that greenhouse gases in the atmosphere absorb infrared radiation emitted from the earth is very well established,9 and is the reason the earth is not cold like the moon. It is also unequivocal that the greenhouse gases are increasing dramati­cally. The onus, therefore, should be on the climate skeptics to explain how this would not lead to global warming.

WHAT IS THE DEBATE ABOUT?

We, the teeming billions of people on earth, are changing the earth’s climate at an unprecedented rate because we are spewing out greenhouse gases and are heading to a disaster, say most climate scientists. Not so, say the skeptics. We are just expe­riencing normal variations in earth’s climate and we should all take a big breath, settle down, and worry about something else. Which is it?

A national debate has raged for the last several decades about whether anthro­pogenic (man-made) sources of carbon dioxide (CO2) and other so-called “green­house gases“ (primarily methane and nitrous oxide) are causing the world to heat up. This phenomenon is usually called “global warming" but it is more appropriate to call it “global climate change" since it is not simply an increase in global tem­peratures but rather more complex changes to the overall climate. Al Gore is a prominent spokesman for the theory that humans are causing an increase in green­house gases leading to global climate change. His movie and book, An Inconvenient Truth, gave the message widespread awareness and resulted in a Nobel Peace Prize for him in 2008. However, the message also led to widespread criticism.

On the one hand are a few scientists and a large segment of the general American public who believe that there is no connection between increased CO2 in the atmosphere and global climate change, or if there is, it is too expensive to do anything about it, anyway. On the other hand is an overwhelming consensus of climate scientists who have produced enormous numbers of research papers demonstrating that increased CO2 is changing the earth’s climate.

The IPCC not only critically analyzes the scientific data regarding greenhouse gases and global climate change, but it makes model-based predictions on future changes according to various emission scenarios.10 If greenhouse gases were held at 2000 levels, the predicted temperature in 2090-2099 compared to 1980-1999 would increase by 0.6°C (likely11 range is 0.3-0.9°C) or 1.1°F. For the low emis­sion scenario, the increase is 1.8°C (1.1-2.9°C) or 3.2°F; for the high emission scenario (basically business as usual), the increase is 4.0°C (2.4-6.4°C) or 7.2°F (1). For the next two decades, there is expected to be warming of about 0.2°C per decade for the various emission scenarios, and there would be a warming of about

0. 1°C per decade even if all greenhouse gases and aerosols were kept constant at year 2000 levels (1). This is because of the slow warming response of the oceans and the very long time that CO2 remains in the atmosphere.

These temperature changes may not seem to be very large, but they have major consequences. In the third IPCC report in 2001, risks of climate change were assessed based on various “reasons for concern.” These reasons for concern include:

• Risks to unique and threatened systems, such as coral reefs, tropical glaciers, endangered species, unique ecosystems, biodiversity hotspots, small island states, and indigenous communities;

• Extreme weather events, such as heat waves, floods, droughts, and tropical cyclones;

• Distribution of impacts, with disparities between various regions and populations that may suffer greater harm, such as extensive drought or high sea levels, compared to those that may actually benefit;

• Aggregate impacts such as monetary damages and lives affected or lost;

• Risk of large-scale discontinuities such as partial or complete melting of Greenland or West Antarctica ice sheets.

A recent update on these reasons for concern based on more current publica­tions shows that all of these risks are greater at lower temperatures than were originally estimated in 2001 (47). This is dramatically illustrated in the famous “burning embers” graphic (Figure 1.10). A 2°C increase in temperature is now expected to have much more severe consequences than previously thought.

The scientific consensus is expressed most clearly in the Fourth Assessment Report in 2007 by the United Nations-sponsored Intergovernmental Panel on Climate

Change (IPCC), the fourth in a series of reports since 1990 (1). The IPCC began as a group of scientists meeting in Geneva in November 1988 to discuss global climate issues under the auspices of the World Meteorological Organization and the United Nations Environment Program. But it had its genesis in the hot sum­mer of 1988. On a sweltering June day in Washington, DC, Senator Tim Wirth of Colorado chaired a committee hearing on climate change. The lead witness was James Hansen, an atmospheric physicist and head of NASA’s Goddard Institute for Space Studies. He proclaimed that global temperature was rising as his com­puter models predicted and that global warming was being caused by greenhouse gases released by human activities. The hearing got a lot of press and began a dialogue between scientists and policy makers. The World Conference on a Changing Atmosphere met in Toronto shortly after the Wirth hearing and called for coordinated policies among countries to reduce CO2 emissions. But public interest flagged as the hot summer faded into fall (2).

Lack of public interest didn’t stop the science, though. The IPCC meeting and subsequent workshops and reviews of what was known scientifically about cli­mate and its control was coordinated by a Swedish meteorologist, Bert Bolin, who was very careful not to let speculation get ahead of the science. The IPCC gave its First Assessment Report to the UN in the fall of 1990 and concluded that the earth was indeed warming and that humans were “substantially increasing the atmospheric concentrations of the greenhouse gases carbon dioxide, methane, chlorofluorocarbons (CFCs) and nitrous oxide.” Furthermore, “the main green­house gas, water vapour, will increase in response to global warming and further enhance it.” But it also concluded that the global warming could be caused by either man-made greenhouse gases or natural climate variability (3).

There was sufficient reason to worry, though, that the United Nations General Assembly called for an international agreement to limit CO2. This was to be ham­mered out at an Earth Summit to be held in Rio de Janeiro in 1992. After a fractious meeting filled with plenty of demagoguery, an agreement was finally signed—the United Nations Framework Convention on Climate Change. It committed devel­oped countries to control their greenhouse gas emissions and to provide financial resources for developing countries to reduce their emissions. It called for devel­oped countries to reduce emissions in 2000 to 1990 levels on a voluntary basis (2).

This was just the beginning. The IPCC prepared a second scientific assessment report in 1995 by even more scientists, again under the careful leadership of Bert Bolin, which built on the conclusions of the first report. The second report sub­stantiated the general conclusions of the first report with more precise data but made an important new conclusion—that there was now “a discernible human influence on global climate” (4)

And then came the infamous meeting in Kyoto in 1997, which aimed to put teeth in the Rio conference agreement. Greenhouse gas emissions had in fact gone up substantially since 1990, so specific targets were to be set. The United States and the European Union had divergent views on emissions targets, but the deadlock was broken by the arrival of Vice President Al Gore. He had already written a seri­ous book, Earth in the Balance, discussing greenhouse gases and global warming (5), and his presence at Kyoto seemed to indicate that the United States was serious about reducing greenhouse gas emissions. The United States, Europe, and Japan agreed to binding targets to reduce CO2 emissions by 6-8% by 2008-2012 com­pared to 1990, with an overall goal of reducing global greenhouse gas emissions by 5% below 1990 levels (6). The second big dispute was between developed and devel­oping countries. Developing countries such as China, India, and Brazil refused to make binding commitments to reduce greenhouse gases since they (rightly) claimed that they had not caused the problem with greenhouse gases. However, as they grew they would become a bigger contributor to the problem. The problem was that the US Senate had made it clear in the Byrd-Hagen Resolution of 1992 that it would not accept a treaty that exempted developing countries. The third dispute arose over how to pay for emissions reductions. The United States had suc­cessfully implemented a cap and trade system to reduce acid rain from coal-fired power plants and wanted that market-oriented model; Europe wanted mandates and governmental intervention. The United States won the argument, and the Kyoto Protocol was signed. But the disagreement over the role of developing coun­tries meant that it could never clear the US Senate. President Bill Clinton never even submitted the treaty for consideration, knowing it would be defeated (2).

The third Scientific Assessment Report for the IPCCin2001 continued to refine the conclusions of previous reports with increasingly accurate data and modeling. It also began to give statistical values to its conclusions. The evidence pointing to the human contribution to global warming was even stronger, with the report concluding that “most of the observed warming over the last 50 years is likely to have been due to the increase in greenhouse gas concentrations”(7)

And the political meetings continued. Political leaders from all over the world met in Copenhagen in late 2009 to discuss global climate change and what can be done to prevent or mitigate it, though they were not able to decide on any course of action (8). They met again in Cancun in late 2010 and signed a modest agreement to begin to tackle global warming. “For the first time all countries are committed to cutting car­bon emissions under an official UN agreement. Rich nations also have to pay a total of £60 billion [$92 billion] annually from 2020 into a “green fund” to help poor countries adapt to floods and droughts. The money will also help developing countries, includ­ing China and India, switch to renewable energy sources including wind and solar power”(9) Also, in late 2009 the US Environmental Protection Agency (EPA) ruled that greenhouse gases pose a danger to the environment and to human health, open­ing the door to regulation of CO2 emissions from automobiles, power plants, factories, and other anthropogenic sources.

But signing agreements and actually doing something about it are two differ­ent things. So far the action to mitigate CO2 emissions has been minimal, espe­cially in the United States. Europe, however, established a cap and trade market in 2003—the European Union’s Emission Trading Scheme—and adopted an ambi­tious goal to reduce CO2 emissions by 20% of 1990 levels by 2020 (2). The United States, meanwhile, failed to get any legislation passed that would establish a cap and trade market to reduce CO2 emissions, and the whole issue became a political hot potato because of widespread Republican opposition.

It is well beyond the scope of this chapter to discuss all of the issues fully, but it is important to consider the science behind the controversy, since the premise of this book is that global climate change is occurring due in large part to anthropo­genic contributions to atmospheric CO2 from burning fossil fuels. So, is it or isn’t it? That is the question.

One of the major concerns about global warming is that sea levels are projected to increase, though not the 20 feet projected by Al Gore (44). The IPCC proj­ects that seas may rise by about 0.2 to 0.6 meters (0.6-1.9 ft.) by the end of the twenty-first century for the various scenarios. However, this may be an underes­timate because of what are known as “tipping elements" that may reach a critical threshold and cause a very large change in a system in a short time frame because of positive feedbacks. A variety of tipping elements were evaluated recently in a special issue of the Proceedings of the National Academy of Sciences (48). The tipping element of largest concern is the melting of ice sheets in Greenland and West Antarctica, which could result in much larger rises in sea level than are predicted by the IPCC (49). It is estimated that global warming of 2°C, at the low end of the overall predictions for warming during the twenty-first century, could lead to slow melting of the Greenland ice sheet, which would lead to a sea level rise of several feet.

Another major concern is the acidification of the oceans, which is already occurring. The pH of the oceans has dropped by about 0.1 pH units from 8.2, the normal pH range. While this may not seem significant, it represents a change of about 30% in the hydrogen ion concentration. The pH may drop to 7.8 if cur­rent trends continue, which would be 150% more acidic than in 1800. The cause of acidification is the formation of carbonic acid from water and CO2. The extra hydrogen ions from the carbonic acid bind to carbonate ions, converting them into bicarbonate ions. This reduces the availability of calcium carbonate. Many ocean creatures that depend on calcium carbonate for shells, including coral pol­yps that make reefs, sea urchins, and plankton could have dramatic changes with uncertain consequences for the ocean food chain. As Elizabeth Kolbert writes, “. . . corals and pteropods are lined up against a global economy built on cheap fos­sil fuels. It’s not a fair fight” (50).

High
Negative Net for Most Negative Regions in All Metrics	Negative for Most Regions	Net Negative in All Metrics
High	Large Increase
Risks to Many
4
0 о сг
3
оз Future 3 T3 Ф m c Ф 03 СГ о < Ф о.
2	2
Negative Positive or Negative Market for Some Impacts; Regions; "Majority Positive of People for Adversely Others Affected
Positive or Negative Market Impacts; Majority of People Adversely Affected
1	Negative for Some Regions; Positive For Others	1
Very Low
Risks to Some
Low
Increase	о о
0	0
Past
Distribution of Impacts
Risk to Unique and Threatened Systems	Risk of Extreme Weather Events

James Hansen, a prolific climate scientist and one of the most outspoken scien­tific proponents of the dangers of global warming from greenhouse gases, shows that sea levels rose 4 to 5 meters (14-17 ft.) per century at the end of the last ice age and argues that similar changes could occur if Greenland and West Antarctica ice sheets melted (30). In the past he has argued that keeping atmospheric CO2 levels below 450 ppm would prevent major environmental catastrophes from occurring. In a 2008 paper (51) and in his recent book Storms of My Grandchildren (30), he argues convincingly from paleoclimate data over the past 65 million years that the ice sheets in Antarctica and Greenland did not exist when CO2 was higher than 450 (±100) ppm, 34 million years ago. If we continue to burn fossil fuels as we are now, increasing CO2 by 2 ppm per year, we will surely exceed that limit in a few decades with very dire consequences likely. He now recommends that we should aim to reduce atmospheric CO2 to 350 ppm to avoid these consequences. This rec­ommendation has been the spur behind the website www.350.org, developed by Bill McKibben, which actively promotes efforts to reduce CO2 to 350 ppm. Recall that the atmosphere is already over 390 ppm CO2.

To answer the question, we first need to understand exactly what is meant by greenhouse gases and how they cause the earth to warm up. The real questions are: Why does the earth have the temperature it has, and what causes it to change? Physics provides the answers. The earth gets its temperature from the energy bombarding it from the sun. The average amount of energy hitting the earth from the sun each second is about 342 watts per square meter (W/m2), but about 30% of this is reflected by clouds and water and ice on the earth’s surface, so about 235 W/ m2 is absorbed by the earth.1 A basic law of physics says that objects that get heated up also have to radiate energy to keep energy in balance, so about 235 W/m2 are also radiated by the earth. The Stefan-Boltzmann law says that the rate at which an object (known as a black body) radiates energy goes up as the fourth power of its temperature (T4). Using this law and the rate at which energy is absorbed and emitted by the earth, you can calculate that a black body earth should have a temperature of about -18°C or 0°F. But that is not what the temperature of the earth actually is—its average temperature is actually about 15°C (59°F) (10). It is lucky that the earth’s temperature is not what the Stefan-Boltzmann law predicts because the earth would be a ball of ice!

So is physics wrong? No, but we didn’t account for the earth’s atmosphere. The atmosphere consists mostly of nitrogen and oxygen but also contains gases known as greenhouse gases—principally water vapor and CO2 but also methane, nitrous oxide, ozone, and a few other minor gases. The energy from the sun is mostly vis­ible light, but when it is absorbed by the earth and radiated back into space, it is radiated as infrared light that has a longer wavelength and less energy than visible light. The earth’s atmosphere is largely transparent to the visible light from the sun, but the greenhouse gases absorb most of the infrared radiation. The nitro­gen and oxygen that form most of the atmosphere do not absorb the infrared radiation, so they do not contribute to warming the earth. So, the simple expla­nation of the greenhouse effect is that the earth is like a greenhouse where the sun’s energy passes through the glass panes but is trapped inside the greenhouse because the infrared radiation can’t pass through the glass—the glass being the greenhouse gases.

A more sophisticated and accurate view is that the infrared radiation is absorbed by the greenhouse gases, which then re-emit the radiation in all directions, with some of it coming back to the earth and some of it heating up the atmosphere and being radiated into space. The net result is that the earth heats up to a higher temperature than it would have if the greenhouse gases didn’t exist. It still has to be in balance energetically, so as the earth gets a higher temperature, it radiates energy at a higher rate—with some of it coming back to earth—until it is balanced to match the incoming solar radiation, according to the Stefan-Boltzmann law (10). The balancing act can take a very long time, however, and the big problem is that currently there is a mismatch. The earth is radiating 0.6 W/m2 less than it is absorbing, inevitably leading to global warming (10, 11)

All of this is non-controversial and natural—it is how the earth and its atmo­sphere work, though there are lots of details glossed over here. The real contro­versy is whether humans are changing the earth’s temperature by adding such large amounts of CO2 (and other greenhouse gases) to the atmosphere that its greenhouse effect is causing the earth to heat up to achieve a new energy balance. That is the question!

While I wrote the first draft of this chapter in the winter of 2009-2010, Washington, DC, was hit with two record-setting snowstorms, there was a foot of snow in Dallas, and 49 states had snow on the ground at one time, which had apparently never hap­pened before in modern record-keeping. Meanwhile, at the 2010 Winter Olympics in Vancouver, BC, the skiing events were delayed for days because there was little snow and the temperatures were so high that the snow was melting. As 2010 unfolded, Russia suffered an extreme heat wave in the summer that caused enormous for­est fires (52). Meanwhile, the United States and much of northern Europe had record-breaking snowfall and cold during the winter of 2010-2011, and again 49 states had snow on the ground at the same time (53). As expected, many people wonder, how can there be global warming with such a cold, snowy period? In fact, this is not at all surprising because, as Tom Friedman has said, we should be think­ing about “global weirding“ rather than global warming (54). As global temperatures rise, extreme weather becomes more frequent (1, 31), but it can be highly variable geographically.

The summer and fall of2012 gave an excellent example of that. Much of the Midwest and western United States suffered extreme drought and record-breaking temperatures, then the superstorm Hurricane Sandy landed in the northeast in late October. Hurricane Sandy caused extensive damage in New Jersey, New York, and Connecticut, mostly due to an unprecedented storm surge that flooded sub­ways and tunnels in New York City and destroyed the New Jersey shore. Estimated damages are up to $60 billion (55). While it is impossible to precisely point the finger at global warming for these extreme weather events, it is exactly the kind of weird weather predicted by the models. Extreme flooding in the United States and England have been linked to global warming for the first time in two recent scientific reports (56).

One can argue about the exact degree of various effects on the earth, humans, and ecosystems from increased global warming due to greenhouse gases (57). One cannot sensibly argue, however, that there will be no deleterious effects, and the possibility exists that there will be major effects. Jared Diamond has described in detail how climate change, among other factors, has tipped societies into col­lapse, depending strongly on how the societies choose to deal with the environ­mental problems they confront (58). Therefore, the question is whether we as a society and a world community are willing to tackle the environmental problems we are creating, for the sake of our grandchildren and for unique and threatened ecosystems.

By far the largest factor in global warming is CO2 emissions from burning fossil fuels (75%), while land use changes such as deforestation account for about 25% of CO2 emissions (1). A substantial part of the fossil fuel emissions comes from burning coal to produce electricity. The rest of this book deals with how we can reduce CO2 emissions from fossil fuels by using alternative energy sources and greatly increasing the use of nuclear power to replace coal as a source for generat­ing

What do the naysayers say? In the popular press, an outspoken, well-respected columnist who consistently downplays the effects of CO2 on global warming— and indeed denies any global warming—is George Will. He claims that there has been no global warming since 1998, that the models that predict global warming are based on “dicey” assumptions, and that scientists are likely to be wrong about global warming, since they also predicted global cooling in 1975 (12). He loves to quote the April 28, 1975, cover story of Newsweek called “The Cooling World” as evidence that scientists don’t know whether the earth is warming or cooling. However, that Newsweek article did not represent the consensus of scientific articles at the time.2 The best way to evaluate these claims is to look at some actual data on temperature and CO2 levels, which we will do shortly.

Many politicians have been vociferous opponents of the science of global warming. Perhaps the most vocal is Senator James Inhofe from Oklahoma, who said in a January 4, 2005, statement on the Senate floor:

As I said on the Senate floor on July 28, 2003, “much of the debate over global warming is predicated on fear, rather than science.” I called the threat of catastrophic global warming the “greatest hoax ever perpetrated on the American people,” a statement that, to put it mildly, was not viewed kindly by environmental extremists and their elitist organizations. I also pointed out, in a lengthy committee report, that those same environmental extremists exploit the issue for fundraising purposes, raking in millions of dollars, even using federal taxpayer dollars to finance their campaigns. (13)

In his view and that of other (mostly Republican) politicians with similar beliefs, this is all a hoax perpetrated by environmentalists. Other politicians, such as the British politician Nigel Lawson, have a more nuanced view but still are convinced that the ultimate consequences of any global climate change are small compared to the economic cost of doing anything about it when there are more pressing human needs (14).

Another common criticism is that if weather forecasters can’t predict the weather accurately within a few days, how on earth can models predict the cli­mate for 50 years in the future? But this argument confuses the difference between weather and climate. Weather is the daily temperature, precipitation, and storm activity, which varies widely over time and geographical areas. The differences between weather and climate are clearly explained in the fourth IPCC report in 2007:

Climate is generally defined as average weather, and as such, climate change and weather are intertwined. Observations can show that there have been changes in weather, and it is the statistics of changes in weather over time that identify climate change. The chaotic nature of weather makes it unpre­dictable beyond a few days. Projecting changes in climate (i. e., long-term average weather) due to changes in atmospheric composition or other fac­tors is a very different and much more manageable issue. As an analogy, while it is impossible to predict the age at which any particular man will die, we can say with high confidence that the average age of death for men in industrialised countries is about 75. (15)