A Global Warming Primer: Answering Your Questions About The Science, The Consequences, and The Solutions

A Global Warming Primer: Answering Your Questions About The Science, The Consequences, and The Solutions

by Jeffrey Bennett


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Product Details

ISBN-13: 9781937548780
Publisher: Big Kid Science
Publication date: 09/01/2016
Pages: 128
Sales rank: 248,168
Product dimensions: 6.90(w) x 9.90(h) x 0.50(d)
Age Range: 13 - 17 Years

About the Author

Jeffrey Bennett has been teaching and writing about global warming for more than 30 years. He holds a B.A. in Biophysics (University of California, San Diego) and an M.S. and Ph.D. in Astrophysics (University of Colorado). He is the author of critically acclaimed books including Beyond UFOs, Math for Life, What is Relativity?, and On Teaching Science. His six books for children have all been selected for launch to the International Space Station for NASA’s new “Story Time From Space” program; along with one previous book of his that went into space, this makes him the only author ever to have had seven books launched into orbit.

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A Global Warming Primer

Answering Your Questions About the Science, the Consequences, and the Solutions

By Jeffrey Bennett, Joan Marsh, Lynn Golbetz

Big Kid Science

Copyright © 2016 Jeffrey Bennett
All rights reserved.
ISBN: 978-1-937548-80-3


The Basic Science — Easy as 1-2-3

What we are now doing to the world ... by adding greenhouse gases to the air at an unprecedented rate ... is new in the experience of the Earth. It is mankind and his activities which are changing the environment of our planet in damaging and dangerous ways.

— British Prime Minister Margaret Thatcher, Nov. 8, 1989 (speech to the United Nations)

We all know that human activities are changing the atmosphere in unexpected and in unprecedented ways.

— President George H. W. Bush, Feb. 5, 1990 (remarks to the Intergovernmental Panel on Climate Change)

The two quotes above show that, more than a quarter century ago, the conservative leaders of both the United Kingdom and the United States were already convinced of the reality and the threat of global warming. What made them so sure? In the case of Thatcher, it probably helped that she was a scientist herself (trained in chemistry), which made it easier for her to recognize the underlying scientific ideas. But Bush was not a scientist, and he and many other people of all political persuasions were still able to understand the same ideas. Why? Because they are not very difficult.

In this first chapter, I'll show you the simple underlying science of global warming. Note that nothing in this chapter is subject to any scientific debate at all, and you'll find that this basic science is accepted even by the scientists who count themselves as ardent skeptics (as evidence, look ahead to the quote that opens chapter 2). To show you just how simple and solid it is, let's begin with an example from astronomy.

A Tale of Two Planets

Figure 1.1 shows the planets Earth and Venus to scale, along with their global average surface temperatures. You can see that both planets are about the same size; they also both have about the same overall composition of rock and metal. But look at the enormous difference in their surface temperatures. Earth has temperatures ideally suited to life and our civilization, while Venus is hot enough to melt lead. If you think about it, you might wonder why two planets that are so similar in size and composition would have such drastically different surface temperatures.

It might be tempting to chalk it up solely to the fact that Venus is closer to the Sun than Earth, but that is not the answer. Figure 1.2 shows part of the Voyage Scale Model Solar System, which shows the sizes and distances of the Sun and planets on a scale of 1 to 10 billion. Notice that while it's true that Venus is closer to the Sun, the difference isn't really all that great, and it's not nearly enough to account for such a large temperature difference by itself. Moreover, Venus's bright clouds reflect so much sunlight that its surface actually absorbs less sunlight than Earth's, which by itself would lead us to expect Venus to be colder than Earth. So why is Venus so hot?

The primary answer is carbon dioxide, a gas that can trap heat and make a planet warmer than it would be otherwise. In fact, as we'll discuss in more detail shortly, both planets would actually be frozen over if they had no carbon dioxide in their atmospheres at all. Earth has just enough carbon dioxide (plus water vapor; see page 13) to make our planet livable, so in that sense, carbon dioxide is a very good thing for life. But Venus has almost 200,000 times as much carbon dioxide in its atmosphere as Earth, and all this carbon dioxide traps so much heat that the entire surface is baked hotter than a pizza oven — providing clear proof that it is possible to have too much of a good thing (figure 1.3).

This story of Venus and Earth contains almost everything you need to understand the basic science of global warming. It shows that gases like carbon dioxide, which we call greenhouse gases, really do make planets warmer than they would be otherwise, and that the more of these gases a planet has, the hotter it will be.

Global Warming 1-2-3

The lesson from our tale of two planets leads directly to the subtitle of this chapter, in which I say that global warming is as easy as 1-2-3. By this, I mean that for all the arguments you may hear in the media, the basic science of global warming can be summarized in three simple statements, which embody two indisputable scientific facts and the inevitable conclusion that follows from them:

1. Fact: Carbon dioxide is a greenhouse gas, by which we mean a gas that traps heat and makes a planet (like Earth or Venus) warmer than it would be otherwise.

2. Fact: Human activity, especially the use of fossil fuels — by which we mean coal, oil, and gas, all of which release carbon dioxide when burned — is adding significantly more of this heat-trapping gas to Earth's atmosphere.

3. Inevitable Conclusion: We should expect the rising carbon dioxide concentration to warm our planet, with the warming becoming more severe as we add more carbon dioxide.

Notice the inevitability of the conclusion: As long as both of the facts are true — and I'll show you why there is no scientific doubt about either of them — then there's really no way around the conclusion that global warming should be expected.

Of course, knowing that global warming is expected doesn't tell us how badly or imminently we'll be affected, and by itself it leaves open the possibility that other factors (such as climate feedbacks) might mitigate or even counteract the expected warming, at least on some time scales. We'll discuss the debate over these issues in chapter 2. First, however, we'll turn our attention to the evidence that supports our two facts.

Evidence for Fact 1 (Carbon Dioxide Makes Planets Warmer)

Fact 1 is that carbon dioxide is a greenhouse gas that makes a planet warmer than it would be otherwise. Now, in Q&A format, we're ready to examine the evidence that makes this a fact rather than a matter of opinion.

Q How do we know that Fact 1 is really a fact?

There is no doubt that higher concentrations of carbon dioxide and other greenhouse gases make planets warmer, because this fact is based on the simple, well-understood, and well-tested physics of what we call the greenhouse effect. Figure 1.4 shows how the greenhouse effect works. Notice the following key ideas:

• The energy that warms Earth comes from sunlight, and in particular from visible light (the kind of light that our eyes can see). Some sunlight is reflected back to space, and the rest is absorbed by the surface (land and oceans).

• Earth must ultimately return the energy it absorbs back to space. The returned energy takes the form of infrared light, which our eyes cannot see.

• Greenhouse gases — which include water vapor (H2O), carbon dioxide (CO2), and methane (CH4, also commonly called natural gas) — are made up of molecules that are particularly good at absorbing infrared light. Each time a greenhouse gas molecule absorbs a photon (the technical name for a "piece" of light) of infrared light, it quickly reemits it as another infrared photon, which may head off in any random direction. This photon can then be absorbed by another greenhouse gas molecule, which does the same thing.

The net result is that greenhouse gases tend to slow the escape of infrared light from the lower atmosphere, while their molecular motions heat the surrounding air. In this way, the greenhouse effect makes the surface and the lower atmosphere warmer than they would be from sunlight alone. The more greenhouse gases present, the greater the degree of surface warming. A blanket offers a good analogy. You stay warmer under a blanket not because the blanket itself provides any heat, but because it slows the escape of your body heat into the cold outside air.

Q How do we know that Earth returns energy to space in the form of infrared light?

It's basic physics, verified by observations. All objects — including the Sun, the planets, and even you — always emit some form of light, but the form depends on the temperature. Hot objects, like the Sun, emit visible light. Cooler objects, like planets and you, emit only infrared light. While we cannot see infrared light with our eyes, we can detect it with infrared cameras and other instruments, and orbiting satellites have directly measured the amount of infrared light being emitted by Earth.

Q Why haven't you mentioned nitrogen and oxygen, which make up most of our atmosphere?

The atmosphere is indeed made mostly of nitrogen and oxygen; together, these two gases make up about 98% of the gas in Earth's atmosphere (77% for nitrogen and 21% for oxygen). However, molecules of nitrogen and oxygen do not absorb infrared light, and therefore do not contribute to the heating of the surface. In other words, without the relatively small amounts of infrared-absorbing greenhouse gases (such as water vapor, carbon dioxide, and methane) that are present in our atmosphere, all the infrared light emitted from Earth's surface would escape directly into space, and our planet would be frozen over.

In case you are wondering why some molecules can absorb infrared light and others cannot, it is a result of their structures. In our atmosphere, nitrogen and oxygen both take the form of molecules in which two atoms are bound together; that is, nitrogen is in the form N2 and oxygen in the form O2. In order to absorb photons of infrared light, molecules must be able to vibrate and rotate. This turns out to be fairly difficult for molecules with only two atoms, particularly when both atoms are the same, as in N2 and O2; that is why these molecules do not contribute to planetary heating. In contrast, vibration and rotation are relatively easy for many molecules with more than two atoms, which is why water vapor (H2O), carbon dioxide (CO2), and methane (CH4) all absorb infrared light effectively, making them greenhouse gases.

Q Are there any other greenhouse gases I should know about?

Although water vapor, carbon dioxide, and methane are the three most important greenhouse gases in Earth's atmosphere, other trace gases can also act as greenhouse gases, which means they can also contribute to warming. Those that you are likely to hear about and that we'll discuss a bit more in this book include nitrous oxide (N2O) and industrial chemicals known as halocarbons, which include chlorofluorocarbons (CFCs).

Q I've heard that "greenhouse effect" is a misnomer. Is that true?

It depends on how picky you want to be. The term comes from botanical greenhouses, but those greenhouses actually trap heat through a different mechanism than planetary atmospheres: Rather than absorbing infrared radiation, greenhouses stay warm primarily by preventing warm air from rising. Nevertheless, atmospheric greenhouse gases and botanical greenhouses have the same net effect of keeping things warmer than they would be otherwise, so I'm personally fine with the term "greenhouse effect."

Q How do we know that greenhouse gases really trap heat?

Two major lines of evidence show conclusively that greenhouse gases trap heat. First, scientists can measure the heat-trapping effects of these gases in the laboratory. Although the actual setups are somewhat more complex, the basic idea is simply to put a gas (such as carbon dioxide) in a tube, shine infrared light at it, and measure how much of that light passes through and how much is absorbed. Such measurements were first made more than 150 years ago by British scientist John Tyndall (figure 1.5) and have been repeated and refined ever since.

Second, we can easily confirm that the greenhouse effect raises actual planetary temperatures in the way we discussed earlier for Earth and Venus. If there were no greenhouse effect, a planet's average temperature would depend only on its distance from the Sun and the relative proportions of sunlight that it absorbs and reflects. I won't bother you with the mathematical details, but they lead to the simple formula that you can see being applied to Earth in figure 1.6. The formula shows that Earth's global average temperature would be well below freezing (–16°C, or +3°F) without greenhouse gases. In other words, we need the greenhouse effect to explain Earth's actual average temperature, which is about 15°C (59°F). The same is true for all other planets: We get correct answers for planetary temperatures only when we use mathematical formulas that include the greenhouse effect.

This brings us back to our tale of two planets. For Earth, we find that without the naturally occurring greenhouse effect, our planet would be too cold for liquid oceans and life as we know it. That is why, as we saw in figure 1.3, the natural greenhouse effect is a very good thing for life on Earth. But Venus, with almost 200,000 times as much carbon dioxide in its atmosphere as Earth, clearly has much too much of this good thing.

Q Why does Venus have so much carbon dioxide in its atmosphere?

Earth actually has about the same total amount of carbon dioxide as Venus, but while Venus's carbon dioxide is virtually all in its atmosphere, nearly all of Earth's is "locked up" in what we call carbonate rocks, the most familiar of which is limestone. The reason for this difference is that Earth has oceans and Venus does not.

On both planets, the original source of carbon dioxide was gas released by volcanoes. On Earth, carbon dioxide dissolves in the oceans (which contain about 60 times as much carbon dioxide as the atmosphere), where it then combines with dissolved minerals to form carbonate rocks (which contain almost 200,000 times as much carbon dioxide as the atmosphere). Venus lacks oceans and therefore cannot dissolve carbon dioxide gas, so it all remains in the atmosphere.

A deeper question is why Earth has oceans and Venus does not, and scientists attribute this to the fact that Venus is closer to the Sun (Venus is about two-thirds as far from the Sun as Earth). You can understand the role of distance from the Sun by thinking about what would happen if Earth were magically moved to Venus's orbit (figure 1.7). The greater intensity of sunlight would immediately raise Earth's average temperature from its current 15°C to about 45°C (113°F). The higher temperature would increase the evaporation of water from the oceans, putting much more water vapor into the atmosphere — and because water vapor is a greenhouse gas, the added water vapor would strengthen the greenhouse effect and drive temperatures even higher. The higher temperatures, in turn, would lead to even more ocean evaporation and more water vapor in the atmosphere, strengthening the greenhouse effect even further. In other words, we'd have a reinforcing feedback process in which each little bit of additional water vapor in the atmosphere would lead to a higher temperature and even more water vapor. The process would rapidly spin out of control, resulting in what scientists call a runaway greenhouse effect. It would not stop until the "moved Earth" became as hot as (or even hotter than) Venus is today.

In fact, something like this probably occurred on Venus long ago. Based on scientific understanding of how the Sun generates energy through nuclear fusion, the Sun should very gradually brighten with time. The rate is so slow that we cannot measure it, but the calculations indicate that the Sun was about 30% dimmer when the planets were born (about 4 ½ billion years ago) than it is today. This means that the young Venus probably had sunlight of not much greater intensity than Earth does today, and some scientists suspect that Venus may have had oceans at that time. As the Sun gradually brightened, Venus grew hotter until a runaway greenhouse effect set in.

Q Does Mars also have a greenhouse effect?

Yes, but it is very weak. The atmosphere of Mars is made mostly of carbon dioxide (about 95%), but the atmosphere is so thin (the surface pressure is less than 1% of that on Earth) that the total amount of carbon dioxide is actually quite small. As a result, Mars is warmed only a little by its greenhouse effect, and its greater distance from the Sun makes it quite cold, with an average surface temperature of –50°C (–58°F). Scientifically, the surprise is that Mars shows clear evidence of having had liquid water on its surface in the past. This means that long ago, Mars must have been much warmer than it is today, which in turn means that it must once have had a much stronger greenhouse effect. Scientists have a pretty good idea of why Mars once had a strong greenhouse effect and why the effect ultimately weakened so much, but the full discussion isn't directly relevant to our topic in this book.

Q Why are you focusing on carbon dioxide, when there's more water vapor (also a greenhouse gas) in the atmosphere?

It's true that there is more water vapor than carbon dioxide in the atmosphere. In fact, there's about 10 times as much water vapor as carbon dioxide, and water vapor does indeed contribute more than carbon dioxide to Earth's overall greenhouse warming. However, carbon dioxide is the more critical gas in setting Earth's temperature.


Excerpted from A Global Warming Primer by Jeffrey Bennett, Joan Marsh, Lynn Golbetz. Copyright © 2016 Jeffrey Bennett. Excerpted by permission of Big Kid Science.
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
Excerpts are provided by Dial-A-Book Inc. solely for the personal use of visitors to this web site.

Table of Contents

Introduction 1

1 The Basic Science-Easy as 1-2-3 3

A Tale of Two Planets 4

Global Warming 1-2-3 6

Evidence for Fact I (Carbon Dioxide Makes Planets Warmer) 7

Q: How do we know that Fact 1 is really a fact? 7

Q: How do we know that Earth returns energy to space in the form of infrared light? 8

Q: Why haven't you mentioned nitrogen and oxygen, which make up most of our atmosphere? 8

Q: Are there any other greenhouse gases I should know about? 9

Q: I've heard that "greenhouse effect" is a misnomer. Is that true? 9

Q: How do we know that greenhouse gases really trap heat? 9

Q: Why does Venus have so much carbon dioxide in its atmosphere? 11

Q: Does Mars also have a greenhouse effect? 12

Q: Why are you focusing on carbon dioxide, when there's more water vapor (also a greenhouse gas) in the atmosphere? 13

Q: Can you be more precise about how long added carbon dioxide remains in the atmosphere? 13

Q: What about other greenhouse gases? 14

Q: What's the bottom line for Fact 1? 14

Evidence for Fact 2 (Human Activity Is Adding Carbon Dioxide to the Atmosphere) 15

Q: How do we know that the atmospheric concentration of carbon dioxide is really rising? 15

Q: What are the small wiggles on the graph? 16

Q: Are measurements at Mauna Loa really representative of the whole world? 16

Q: Can we measure the carbon dioxide concentration further into the past? 16

Q: How do we know the added carbon dioxide is a result of human activity, rather than natural sources? 18

Q: Does all the carbon dioxide released by human activity add to the atmospheric concentration? 20

Q: Wait - I heard that the amount of carbon dioxide released by human activity is very small compared to the amount released by natural sources like the oceans and living organisms. So why do you say that the natural sources aren't contributing to the increase? 20

Q: Is human activity also increasing the concentrations of other greenhouse gases? 22

Q: What's the bottom line for Pact 2? 24

Global Warming 1-2-3: The Inevitable Conclusion 24

2 The Skeptic Debate 25

Skeptic Claim I: Earth Is Not Warming Up as Expected 26

Q: Is the world actually warming up? 26

Q: Are these temperature data reliable? 26

Q: How much uncertainty is there in the data infigurc 2.1? 28

Q: Wait - I've heard that global warming has stopped since the late 1990s. Is the world still warming up? 28

Q: Still, shouldn't there be some explanation for the slowing? 29

Q: I recently read of a data reanalysis suggesting that there was no slowing. What's up with that? 31

Q: Does the warming match up with what we might expect from the carbon dioxide rise? 31

Q: So is there anyway that Skeptic Claim 1 could be correct? 31

Skeptic Claim 2: It's Warming Up, but it's Natural 32

Q: Could the Sun be the cause of the observed global warming? 32

Q: Can you explain the curves in figure 2.5 more clearly, including why they use an 11-year average? 33

Q: Could it be other natural factors besides the Sun? 34

Q: Why are you saying "models" in plural? 36

Q: What's the bottom line for Skeptic Claim 2? 37

Skeptic Claim 3: It's Warming Up, Humans Are Causing It, but It's Nothing to Worry About 38

Skeptic Claim 3, Part I: Natural Climate Variability 38

Q: Earth has had many ice ages that had nothing to do with humans; how do those natural climate changes compare to what we're experiencing today? 38

Q: What causes the natural cycles of ice ages and warm periods? 40

Q: I heard that the temperature changes in the ice core record precede the carbon dioxide changes. Doesn't this mean that you have cause and effect backward? 40

Q: What about the Medieval Warm Period, when Greenland was "green"? Doesn't that mean that we've been through much warmer periods in the recent past? 42

Q: Wait - didn't I hear that the hockey stick graph has been discredited? 42

Q: You've Looked back 800,000 years, but I've heard that if you go back further, both carbon dioxide levels and temperatures were significantly higher than they are today. What do you say to that? 44

Skeptic Claim 3, Part 2: The Reliability of Models 45

Q: Today's models can't even predict the weather more than a few days out, so how could they possibly predict the effects of global warming many years from now? 46

Q: OK, but maybe the models are missing an important mitigating factor. For example, aren't there uncertainties about the effects of clouds? 47

Q: Still, given the complexity of the climate and the uncertainties of the models, isn't it reasonable to think that other feedbacks may mitigate the threat? 48

Q: What if I still don't trust the models? 49

Q: What's the bottom line on the possibility that temperatures won't rise as much as the basic science might make us expect? 49

Skeptic Claim 3, Part 3; Benefits May Outweigh the Risks 49

Q: Could the added carbon dioxide help plant growth and agriculture? 50

Q: Won't the melting of Arctic ice be good for us in opening up the Arctic sea? 50

Q: So how much credence should I give to the skeptic arguments overall? 51

Skeptic Claim 4: It's Warming Up, Humans Are Causing St, Its Harmful, But It's Not Cost-Effective to Solve It 52

The Expected Consequences 53

Q: What is the basic science behind the consequences of global warming? 53

Q: Can you give us an analogy to explain why the extra energy trapped by a stronger greenhouse effect will do more than just warm the planet? 55

Q: How much energy is global warming adding to the atmosphere? 55

Regional Climate Change 56

Q: What evidence shows that regional climate change is already occurring? 56

Q: Besides the temperature changes, what else happens as a result of regional climate change? 57

Q: What future effects can we expect from regional climate change? 59

Q: I've heard concern about thawing of permafrost; could that amplify these effects? 60

Storms and Extreme Weather 60

Q: Can we tie particular storms to global warming? 60

Q: Are we certain that extreme weather events are increasing? 61

Q: We've had some extremely cold winters lately; doesn't that undermine the argument for global warming? 62

Q: Should we expect heat waves to become more common than cold spells? 62

Melting of Sea Ice 62

Q: Why is the decline of sea ice likely to be detrimental? 64

Q: Why doesn't melting sea ice affect sea level? 64

Q: What evidence indicates that sea ice is declining in the Arctic Ocean? 65

Q: You've shown the sea ice for 2012, which was a record low year. Is that fair? 65

Sea Level Rise 66

Q: How much is sea level rising due to thermal expansion? 67

Q: Why do the satellite data and tidal data differ in figure 3.11? 68

Q: How much will sea level rise due to melting ice? 68

Q: I've recently heard people say that the Antarctic ice cap is actually growing, not shrinking. Are you sure that ice is actually melting into the sea? 69

Q: What if the polar caps melted completely? 71

Q: Should I sell my beach-front real estate? 71

Ocean Acidification 72

Q: What evidence indicates that the oceans are actually acidifying? 72

Q: What's the bottom line for the expected consequences of global warming? 72

4 The Solution 75

Replacement Energy Technologies 77

Q: What is the role of energy efficiency? 77

Q: Could we replace fossil fuels with renewable energy? 78

Q: Should we build new nuclear power plants? 79

Q: So bottom line, do we have the necessary technology to end our fossil fuel dependence? 81

Q: Why haven't you suggested "clean coal," in which we sequester the carbon dioxide? 82

Q: What about tracking and using natural gas as a "bridge fuel"? 82

Future Energy Technologies 83

Q: Why do you think it's worth looking into fusion? 83

Q: What do you mean by solar energy from space? 84

Q: What are microbe-based biofuels? 85

Q: What about geoengineering? 86

Q: If future geoengineering technologies may be able to reverse global warming, can't we just wait for those instead of dealing with the problem now? 87

The Obstacle to a Solution 88

Q: Are there socialized energy costs that almost everyone agrees on? 88

Q: What additional energy costs are currently socialized? 90

Q: Are you saying that politicians who favor the status quo of energy pricing are secretly socialists? 91

The Clear Pathway to the Future 91

Q: How can we institute a true free market for energy? 92

Q: What about "cap and trade" instead of a carbon tax? 93

Q: What about other governmental approaches to dealing with global warming, such as subsidies for solar and wind, regulations supporting mileage standards for vehicles, and so on? 94

A Letter to Your Grandchildren 95

Acknowledgments 99

To Learn More 101

Index 103

About the Author 107

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A Global Warming Primer: Answering Your Questions About The Science, The Consequences, and The Solutions 5 out of 5 based on 0 ratings. 1 reviews.
Anonymous More than 1 year ago
Should be required reading for every elected official.