Too Hot to Handle?
[Carl] Sagan called [the earth] a pale blue dot and noted that everything that has ever happened in all of human history has happened on that tiny pixel. All the triumphs and tragedies. All the wars. All the famines. It is our only home. And that is what is at stake—to have a future as a civilization. I believe this is a moral issue. It is our time to rise again to secure our future.
—Al Gore, An Inconvenient Truth, 2006
Imagine taking a time machine to the final half of the age of dinosaurs. Known as the Cretaceous Period, it spanned the interval of time from 145 million years ago until 65 million years ago, a total of 80 million years. This is 15 million years longer than the entire duration of the “age of mammals,” or Cenozoic era, which has lasted for the past 65 million years. If you stepped out of the time machine, you would not recognize much of the landscape and not just because dinosaurs ruled the world. The Rocky Mountains did not exist; most of California, Oregon, and Washington did not exist; and the Appalachians were not nearly so deeply eroded as they are today. The most notice able difference would have been a huge shallow seaway filled with predatory marine reptiles, such as mosasaurs, plesiosaurs, ichthyosaurs, and sea turtles, as well as gigantic fish, with huge flying reptiles soaring overhead. Today, if you go to western Kansas or South Dakota, you find the ancient marine beds filled with these marine reptile fossils. The Western Interior Cretaceous Seaway (fig. 10.1) once extended all the way from the Arctic Ocean to the Gulf of Mexico, flooding the entire Great Plains and much of the future Rocky Mountain region, cutting North America in half. Although it was only a few hundred meters deep at its deepest, it was an impassable barrier for land animals. The dinosaurs of Montana, Alberta, or New Mexico, which lived on the western shore of this seaway, had more in common with the dinosaurs of Mongolia than with the dinosaurs of New Jersey because there was a temperate-forest land bridge over the Bering Strait to Asia.
Fig. 10.1. Map showing the high sea levels of the Cretaceous that drowned the continents in many parts of the world and made it easier for dinosaurs from Montana to walk to Mongolia than to New Jersey. (Original drawing by Pat Linse)
That would be the second striking fact about the Cretaceous world: instead of polar ice caps, the Arctic and Antarctic were temperate or even subtropical, with abundant trees, and a large fauna of dinosaurs, turtles, crocodiles, frogs, salamanders, and other animals living there. Many animals, such as crocodiles, cannot tolerate even the slightest freezing temperature, so they must have lived in relatively mild conditions even though above the Arctic and Antarctic circles the winters mean six months of darkness. For example, Cretaceous rocks on the North Slope of Alaska (below freezing most of the year today) yield abundant fossils of bald cypress, cycads, ginkgoes, ferns, and many other temperate and subtropical plants typically found in the swamps of Georgia or Florida today. Instead of the subfreezing annual temperatures, the summer temperatures in the region were about 10°C (50°F), or cool temperate.
This is also true of the southern polar regions. Decades of work in southern Australia and even in Antarctica show the region inside the Antarctic Circle supported a varied fauna of dinosaurs, fish, turtles, flying pterosaurs, birds, amphibians, and even small mammals. The temperatures were similar to Alaska at the time, with lush, green vegetation. It included ferns, ginkgoes, cycads, podocarps (“yew pines”), numerous flowering plants, and Araucaria trees (known today as the Norfolk Island pine, or the monkey-puzzle tree). As in the Arctic, these plants could tolerate six months of darkness but not freezing, so they would have been dormant about half the year. Dinosaurs show an interesting mixture of ecologies. Most dinosaurs from Alaska are the same as the duckbill dinosaurs in southern Alberta, so it is reasonable to assume that they migrated from the region in herds during the winter darkness and returned in the summer (as most Arctic animals do today). Many dinosaurs from southern Australia, however, are small bodied and could not migrate. Their bones have clear growth lines, suggesting dormancy or hibernation half the year. Other Australian Cretaceous dinosaurs show no such growth lines and have large eye sockets, which support the notion that they were active year round and used their large eyes to see in the dim world of polar winter.
How could these animals and plants survive six months of darkness each year? Temperatures had to be mild, because so many of these organisms are intolerant of freezing conditions. Most paleoceanographers agree that polar regions must have been bathed in oceanic currents coming up from the tropics, which kept the climate mild and minimized the temperature difference between the poles and the equator. In addition to the absence of ice anywhere on the planet, melting polar ice caps would help explain why sea levels rose and drowned the continents, forming the Western Interior Seaway (fig. 10.1). Finally, paleoclimatologists have found numerous lines of evidence indicating atmospheric carbon dioxide must have been about 2,000 ppm (parts per million), almost 10 times the pre–Industrial Revolution values of 270 ppm. This was a true “greenhouse planet,” with no ice or polar ice caps, high sea levels, and very high levels of greenhouse gases like carbon dioxide in the atmosphere.
Where did all this carbon dioxide come from? A number of potential sources have been discovered by geologists over the past decades of research. One factor was that the supercontinent of Pangea (fig. 9.7) was breaking up rapidly during the Cretaceous. The ocean floor was spreading apart at rates never seen again in earth history as the continents raced away from one another. Seafloor spreading brings up huge volumes of volcanic gases from the earth’s mantle, among which are abundant greenhouse gases such as carbon dioxide. Another contributing factor are huge lava eruptions straight from “hot spots” or plumes of molten material in the mantle. Most of these eruptions occurred beneath the ocean, piling up huge volumes of basalts in submarine plateaus such as the Ontong Java Plateau in the western Pacific. This plateau (one of many now known) consists of 1.5 million cubic kilometers (360,000 cubic miles) of lava erupted in less than a 1-million-year interval about 122 million years ago. Other similar plateaus include the Hess Plateau, the Kerguelen Plateau, and the Shatsky Rise, all of which would have poured immense amounts of carbon dioxide into the Cretaceous atmosphere. There is no problem with producing the Cretaceous greenhouse atmosphere given the ongoing geologic events. The problems remain in the details of when the carbon dioxide erupted, and how these events match the changes in sea level that occurred throughout the Cretaceous.
This “greenhouse of the dinosaurs” reached an even hotter level in the early Eocene, about 55 million years ago. At that time, a huge “burp” of methane was released from ice crystals embedded in oceanic sediment, and suddenly global temperatures rose higher than they had been for 300 million years. For example, in the Canadian Arctic are plant fossils that suggest even warmer conditions than in the Cretaceous. These plants include sequoias, dawn redwoods, elms, oaks, Liquidambar, ginkgoes, Viburnum, and bald cypresses. On the basis of modern forest analogues, the mean annual temperature in the Canadian Arctic was as high as 25°C (77°F), or temperate to subtropical. Living in those forests were abundant crocodilians, pond turtles, amphibians, monitor lizards, garfish, as well as primitive horses, tapirs, rhinoceroses, lemurlike primates, rodents, and many other creatures that required a dense forest with ponds and subtropical conditions to survive.
This greenhouse world came to a slow end throughout the 21 million years of the Eocene (55–34 million years ago). It climaxed with the appearance of glacial ice caps on Antarctica 33 million years ago, which marked the beginning of the modern icehouse world. As discussed in chapter 9, the end of the “greenhouse of the dinosaurs” is a complex story, which certainly involves some mechanism of lowering carbon dioxide in the atmosphere and may be a function of changes in oceanic circulation and the development of the Circum-Antarctic Current (fig. 9.5). The full details of this story are given at length in my book, Greenhouse of the Dinosaurs (Prothero 2009, chap. 8).
Fig. 10.2. Typical example of fossiliferous limestones from the Midwest, showing the continent was drowned during most of the Paleozoic by enormous shallow tropical seas, something like the Bahamas but on a continental scale. A, Early Carboniferous limestone from Illinois, made entirely of the pieces of crinoids, or “sea lilies.” It is estimated that several trillion of these animals made up units such as the Burlington Limestone. B, An Ordovician outcrop from near Cincinnati, with two large coral heads growing one on top of the other. (Photos by the author)
Was the “greenhouse of the dinosaurs” a unique event in geologic history? No! If you travel across the Midwest and many parts of the Rockies and the Colorado Plateau, almost every Paleozoic outcrop and road cut consist of fossiliferous marine rocks produced in shallow tropical seas that covered the planet from 600 million to 320 million years ago (fig. 10.2). These include the fossiliferous marine shales and limestones around Cincinnati, Ohio; the incredibly fossiliferous limestone quarries of Indiana, Illinois, and Iowa; the great limestones of Kentucky from which Mammoth Cave was etched—or similar limestones like the Redwall limestone in the Grand Canyon, the Madison limestone in the northern Rockies, or the Pahasapa limestone in the Black Hills. All are products of another huge tropical seaway that drowned the entire continent except for small areas (like the Appalachian Mountains) that emerged from the waves. During this time span, there were few or no glacial ice caps on the polar continents, and carbon dioxide must have been at levels comparable to the 2,000 ppm of the Cretaceous.
Thus, we have greenhouse worlds between the Cambrian and early Carboniferous (600–320 million years ago) and in the later Mesozoic to Eocene (200–33 million years ago), and icehouse worlds of the “snowball earth” (700–600 million years ago), the great Permian Gondwana ice sheet (fig. 9.7) of 320–200 million years ago, and the current icehouse world from 33 million years ago until now (fig. 10.3). Three icehouses separated by two greenhouses over roughly 500–600 million years. Some geologists calculate a roughly 250–million-year-long greenhouse-icehouse cycle, and many suggestions have been proposed to explain this apparent cyclicity. However, it is difficult to make the case that there is a true alternation of two stable states here, because there are only 2.5 “cycles” in all, not enough events to make the case statistically. In addition, it does not appear that the causes of each transition are comparable or even similar. For example, the greenhouse-icehouse transition that occurred 320 million years ago was probably triggered by carbon dioxide trapped in huge coal deposits (see chapter 9), but no such similar event took place 33 million years ago during the last greenhouse-icehouse transition. Arguments about the possible causes of these events continue, but whatever direction the discussion takes, it is clear that the earth has had long periods of greenhouse climates with no polar ice caps, high carbon dioxide levels in the atmosphere, and sea levels that drowned most of the lower elevations of the continents.
Looking back at past greenhouse worlds gives us a different perspective on the global climate change our planet is experiencing. As we saw in chapter 9 (fig. 9.10), if the normal glacial-interglacial cycles of our current icehouse world were allowed to operate naturally, we should have begun heading into the next glacial cycle any time now. As we shall see later, the opposite is the case. The planet is already measurably warmer than it has been in any interglacial in the past 2 million years, with carbon dioxide levels at 400 ppm and headed up past 600 ppm, higher than at any time in the past 5 million years. In the discussion that follows, we shall see some of the many effects of this “superinterglacial” greenhouse world we are inflicting on the planet.
Fig. 10.3. The “greenhouse-icehouse” cycles of the past 600 million years. (Image by author; redrawn by Pat Linse)
How did scientists discover that the planet was undergoing global warming? As early as 1896, the Nobel Prize–winning Swedish chemist Svante Arrhenius showed that carbon dioxide was a powerful greenhouse gas. He realized that when the earth receives energy through solar radiation it comes in short wavelengths (mostly visible light and ultraviolet) that penetrate any atmospheric gases. Once the solar radiation is absorbed by the earth, the energy radiates back out as heat (infrared radiation), a long-wavelength form of energy blocked by greenhouse gases. Unable to radiate back into space, heat accumulates in the earth’s atmosphere and contributes to global warming. Thus, the greenhouse gases act like the glass ceiling of a gardener’s greenhouse, locking in heat but letting the light through. In 1896, Arrhenius calculated that doubling the level of atmospheric carbon dioxide would cause global temperatures to rise by 5°–6°C. This is remarkably close to the current estimates of scientists in the Intergovernmental Panel on Climate Change (IPCC) report in 2007, published more than a century later with more data and better instrumentation than was available to Arrhenius.
Atmospheric scientists occasionally discussed global warming and the greenhouse effect over the next 60 years, but no real systematic experiments to measure its effects were undertaken until 1958. Then Charles D. Keeling began his first measurements of atmospheric carbon dioxide that continue today, a half-century later. Keeling was trained as a geochemist at the University of Illinois and Northwestern University and then as a postdoctoral student at Caltech, where he invented one of the first devices for measuring carbon dioxide in the atmosphere. In 1956, he was hired at the Scripps Institute of Oceanography near San Diego to begin work on measuring changes in the earth’s atmospheric carbon dioxide. Spurred by the legendary geologist Roger Revelle, Keeling used funding from the famous International Geophysical Year program to begin his research. In 1958, he began measuring both in Antarctica and atop Mauna Loa, an extinct volcano in Hawaii, as well as a few other places. Most of these places were chosen because they were far from the effects of local cities or large forests and continents, so they gave the best possible averages for the global atmosphere.
Fig. 10.4. The “Keeling Curve” of the increase in atmospheric carbon dioxide since 1958. (Modified from image at Globalwarmingart.com; redrawn by Pat Linse)
By 1960, the second year of his experiment, he could already see the mean values climbing dramatically (fig. 10.4). After a few years, his funding from the National Science Foundation ended because his results were considered “routine.” They were uninterested in supporting any long-term research that might take more than three to five years. This is typical of the vagaries of science funding in the United States, where safe short-term projects get all the regular funding, but long-term projects, or more daring projects that don’t guarantee success have no chance at money. Ironically, after the National Science Foundation cut his funding, they still used his results to warn the government about the dangers of global warming.
Keeling had to abandon his expensive trips to Antarctica, and he and Revelle scraped up enough money each year to keep the Mauna Loa Observatory going—and it is still collecting data today, more than 52 years later, making it the longest continuously collected data set on global climate anywhere in the world. Today, the Mauna Loa Observatory is a large facility, with numerous buildings and different experiments, well funded by the National Oceanic and Atmospheric Administration. It is an important landmark in the history of science, just as Mount Wilson Observatory in the mountains above Pasadena is the birthplace of the discovery of the expanding universe and the “Big Bang” theory.
Keeling’s experiments generated the famous “Keeling Curve” showing the increase in carbon dioxide since 1958 (fig. 10.4). As already mentioned, it shows a dramatically increasing trend, year by year. There are also seasonal up-and-down cycles of carbon dioxide caused when Northern Hemisphere plants absorb the gas in the spring and then release it when they die back in the fall and winter. Such a monotonic change should have already been evident, but it always helps to look over longer time frames to see whether the increase is part of a “natural variation.” This has been done on many different timescales. For example, in the famous temperature plot (fig. 10.5) of the past 1,000 years of temperature data (Mann et al. 1999), the past 900-plus years are reconstructed from tree rings, ice cores, corals, and other climatic indicators. The final century of data points comes from direct measurements. No matter which data sets are used the results are similar. Climate was stable within a narrow band through the past 1,000, 2,000, or even 10,000 years of the Holocene, with just slight warming events during the Climatic Optimum about 7,000 years ago, and the slight cooling of the Little Ice Age from the 1700s and 1800s. But the magnitude and rapidity of the warming represented by the past 200 years is simply unprecedented in all of human history—and it exactly coincides with the Industrial Revolution, when humans first began massive deforestation and burning coal, gas, and oil in large quantities, which released huge amounts of carbon dioxide. This is the clearest possible “smoking gun” for human culpability for global warming because no other explanation comes close to making sense of it. The curve is now legendary and known by the nickname “the hockey stick curve” because of its long, straight “shaft” of no net change before 1800, followed by the rapid curve upward at the end of the hockey stick.
Fig. 10.5. The record of the last 1,000 years of temperature change (after Mann et al. 1999), which was stable until the late 1800s, when it suddenly shot upward in response to greenhouse gases released by the Industrial Revolution. The long straight line with the sudden kick upward gave it the nickname the “hockey stick curve.” (Modified from image at Globalwarmingart.com; redrawn by Pat Linse)
The data presented so far are clear-cut and beyond dispute among climate scientists. They represent an amazingly uniform consensus about climate change by nearly every scientist who works on the problem directly and publishes in top peer-reviewed journals. Such a group of scientists made up the IPCC, which was unequivocal in warning about the dangers of global warming and that humans were largely responsible. Their work was honored with the 2007 Nobel Peace Prize, shared with former vice president (and Oscar winner) Al Gore, who helped publicize it with his lectures depicted in the documentary film An Inconvenient Truth. The same basic conclusions have been endorsed by all leading scientific societies in nearly every nation of the world, and especially the most prestigious ones, the national academies of every nation that has spoken on the topic.
If that were not enough evidence, plenty of unbiased surveys show the depth and breadth of consensus among mainstream scientists that global warming is real and a serious threat to humanity. The most famous of these was conducted by Naomi Oreskes in 2004, which looked at all papers published on the topic in the world’s leading scientific journal, Science, between 1993 and 2003. Of the hundreds of papers written by the world’s top scientists, 980 supported global warming and none opposed it. A more recent study (Doran and Kendall Zimmerman 2009) found the support among the geophysical and atmospheric scientific community was virtually unanimous. This was confirmed when the prestigious Proceedings of the National Academy of Sciences (USA) published a paper showing that 98 percent of all scientists who actually publish climate research agree that global warming is real and caused by humans (Anderegg et al. 2010). I can think of no other topic in science (except evolution) that has this level of agreement among nearly all the world’s leading scientists, especially among scientists who actually work with the scientific data and know the problem intimately. If it were not such a controversial topic politically, there would be almost no interest in discussing it among scientists, the evidence is so clear cut.
Right-wing politicians, Web sites, blogs, and Fox News continue to claim that global warming is still “controversial” or “unproven” and cite support in the scientific community. They can dredge up a few scientists here or there who are climate skeptics. One poll conducted by denialists led by Oklahoma senator James Inhofe (who receives major political contributions from the oil industry) attempted to show that there were at least a few hundred scientists who did not agree with the consensus about global warming. On closer inspection, the Center for Inquiry (CFI; www.centerforinquiry.net/) found that fewer than 10 percent of the names on the list had any appropriate credentials or direct experience in climate research. Instead, they were a mixture of scientists with no relevant training or experience. More than 80 percent had no refereed publications in climate science at all. About 4 percent of the denialists on the list actually protested their inclusion because they favored the IPCC 2007 consensus that global warming is real and man-made. Dr. Stuart Jordan, formerly a climate scientist for NASA and now with the CFI, wrote, “As a result of our assessment, Inhofe and other lawmakers using this report to block proposed legislation to address the harmful effects of climate change must face an inconvenient truth: while there are indeed some well respected scientists on the list, the vast majority are neither climate scientists, nor have they published in fields that bear directly on climate science” (Center for Inquiry 2007). Dr. Ronald Lindsey of CFI wrote, “Sen. Inhofe and others have had some success in conveying to the media the impression that the number of scientists skeptical about man-made global warming is swelling, yet this is demonstrably not true” (Center for Inquiry 2007). Inhofe’s office had misleadingly claimed that the number of dissenting scientists was 13 times more than the number of United Nations scientists (52) who authored the 2007 IPCC. “But those 52 U.N. scientists were in fact summarizing for policymakers the work of over 2,000 active research scientists, all with substantially similar views on global warming and its causes. This is the kind of broadside against sound science and scientific integrity that we at CFI deplore” (Center for Inquiry 2007). The tactic of beating the bushes for any “expert” who will dissent from a legitimate scientific consensus resembles creationists’ tactics. They frequently tout “lists of Ph.D. scientists who doubt evolution”; however, these lists consist of people with no relevant training, mostly nonscientists, plus a few engineers, chemists, or physicists. None of these “dissenting scientists” have firsthand research experience in geology, biology, or paleontology, and those who claim to be “geologists” or “biologists” got their degrees from creationist diploma mills. The National Center for Science Education cleverly parodied this misleading approach to cherry-picking names with “Project Steve” (http://ncseweb.org/taking-action/project-steve). It consists entirely of PhD scientists whose first name is Steve (less than 1% of all scientists) and who accept evolution—and that list alone far outnumbers all the “creationist scientists” put together.
Always check the credentials of people who write books about climate science. If they lack a PhD in climate science and are not actively researching climate science and publishing in respected journals of climate science, then they are amateurs in that topic and don’t deserve to be taken seriously. This applies to many books and other writings that claim to show that there is no problem with global warming. For example, Bjorn Lomborg’s book, The Skeptical Environmentalist, made a big splash when it first appeared, but Lomborg has no credentials in any science, and his work has been destroyed by many different groups of scientists who have revealed him to be incompetent in scientific issues (let alone his economic claims). More recently, people have carefully checked his footnotes and sources, and found that he has been quoting out of context (like a creationist), and most of his “sources” do not support the claims he makes in his book but have the opposite meaning. In August 2010, even Lomborg admitted that global warming was real and represented a serious threat to humanity.
Ian Plimer’s recent book, Heaven and Earth: Global Warming, the Missing Science (2009) received more attention because Plimer is a geologist; however, Plimer is a mining geologist, not a climate scientist, and he (along with oil geologists) would be expected to have a vested interest in not understanding climate data that threatens his livelihood. His incompetence in climate science was revealed in numerous, scathing book reviews by both climate scientists and earth scientists (e.g., “Plimer’s Homework Assignment,” www.realclimate.org/index.php/archives/2009/08/plimers-homework-assignment/; “The Science is Missing from Ian Plimer’s “Heaven and Earth,” http://science blogs.com/deltoid/2009/04/the_science_is_missing_from_ia.php).
A favorite tactic of the anti-science movement such as creationism and climate denialism is to quote scientists out of context (called “quote mining”) to support their position. When the full citation is consulted, it is clear that the misquotation contradicts the original author’s intended meaning. This was particularly apparent in the attempt to distort the meaning in the wording of a few stolen e-mails from the Climate Research Unit of the University of East Anglia. If you read the actual e-mails and understand the context of the language used by climate scientists when talking casually to one another, it is clear that there was no great “conspiracy” or that they were faking data (www.realclimate.org/index.php/archives/2009/11/the-cru-hack/). This is one of the most dishonest tactics of all, because quote-miner climate denialists are either deliberately trying to mislead their audience by distorting the evidence or do not understand the quotes and their context in the first place.
Climate denialists, like creationists and Holocaust deniers, have many other traits in common. They pick on small disagreements between different labs as if scientists can’t get their story straight, when in reality there is always a fair amount of give-and-take between competing labs as they try to get the answer right before the other lab does. When competing labs around the world have reached a consensus and arrive at the same answer, there is no longer any reason to doubt their common conclusion. The anti-scientists of creationism and climate denialism will also point to small errors by individuals to argue that the entire enterprise cannot be trusted. Scientists are human and can make mistakes, but the great power of the scientific method is that peer review weeds these out, so that when they speak with consensus, there is no doubt that their data are solid. Finally, the most convincing evidence that this is a purely political controversy, rather than a scientific debate, is that membership lists of creationists and climate denialists are mostly identical. Both are fed to overlapping audiences through right-wing media such as Fox News and Rush Limbaugh. The intelligent-design creationism Web site for the Discovery Institute (www.discovery.org/) lately posts items that have nothing to do with creationism at all but are focused on climate denialism and other right-wing causes.
A number of journalists and researchers have documented (McCright and Dunlap, 2003; Williams 2005; Curry et al. 2006; Mooney 2006, 2007; Hoggan, 2009; Oreskes and Conway, 2010) that the movement to deny global warming was not some rebellion scientists critical of the consensus spontaneously generated. It turns out to be a well-funded disinformation campaign supported by oil money to sow seeds of doubt about global warming. A number of memos and documents that were leaked out revealed that the entire movement was a giant public relations effort, not something real scientists would do in the unbiased pursuit of truth. Many have compared the denialist effort to how tobacco lobbyists tried to create a disinformation campaign of doubt. For decades, they forestalled any political action against tobacco by trying to prevent people from recognizing that smoking will kill you. In one particular instance, the oil lobby (through intermediaries) actually advertised and put up money to beat the bushes and find scientists—any scientists—who would dispute the consensus in some way. This is comparable to the practice of defense attorneys calling on highly paid, but unqualified, “expert” witnesses to confuse the jury about relatively clear-cut scientific facts. As Mooney (2006) and others documented, the Bush administration even had oil company lobbyists with no scientific qualifications placed high in their government bureaucracies. These unqualified political hacks edited government scientific reports to tone down the global warming emphasis or censored scientists altogether if their message was inconvenient to energy industry lobbyists.
Disinformation campaigns have had an effect. Numerous polls show that about 40 percent to 50 percent of Americans are still unsure about global warming or think that there is no scientific consensus. Numbers apparently improved after Al Gore’s movie An Inconvenient Truth became a hit and changed the minds of many people, but still they represent a significant number of Americans who have bought into the disinformation campaign and don’t trust the scientific consensus.
Let’s set aside politics and look at the best available scientific data on why the climate science community considers global warming to be established beyond a reasonable doubt. Most common lies and myths about global warming are answered on the Web sites Grist (www.skepticalscience.com) and RealClimate (www.realclimate.org), so there is no need to repeat every argument here. I’ve already outlined the huge amount of climate data that have been available since 1999, and that data set keeps getting larger. Every new observation— from rapidly melting glaciers and ice caps to rising oceanic temperatures to rising sea level—is consistent with global climate change. The most common myth propagated by those who would deny global warming is that somehow this final 200 years of increasing temperature and carbon dioxide is part of a “natural cycle” of climate variability and nothing to be concerned about. As the “hockey stick curve” (fig. 10.5) shows, however, the rise in temperature is unprecedented over the past 1,000 years, and plots of the past 10,000 years show the same trend. The warming documented over the past century is faster and hotter than even the previous warmest period of the Holocene, or “Climatic Optimum,” about 6,000–7,000 years ago.
Maybe 10,000 years is not convincing enough. Let’s look at 680,000 years of climate change. We have such amazing records in long ice cores taken from Greenland and Antarctica. After these cores are drilled and brought up, they are carefully stored until trapped air bubbles from thousands to hundreds of thousands of years ago can be analyzed for their carbon dioxide and oxygen isotope contents. The most impressive of these is the EPICA core from Dome C on Dronning Maud Land, Antarctica (Siegenthaler et al. 2005; Spahni et al. 2005; fig. 10.6). It shows at least six or seven of the 100,000-year-long glacial-interglacial cycles, going back to almost 700,000 years ago. In the wiggly lines, you can see the carbon dioxide measurements for every stage of the glacials and interglacials, including the warmest periods of all seven previous interglacials. At no time during any previous interglacial cycle did the carbon dioxide levels exceed 300 ppm, even at their warmest. The earth’s atmospheric carbon dioxide is already close to 400 ppm today and is headed to 600 ppm within a few decades, even if the release of greenhouse gases stopped immediately. This is decidedly not within the normal range of “climatic variability” but clearly unprecedented in human history. This is the point Gore made in An Inconvenient Truth when he stands atop the scissor lift and rides it upward to show the future levels of carbon dioxide on the long-term climate curve. It may have been a bit corny as a theatrical device, but it got the point across.
Fig. 10.6. Almost 800,000 years of temperature and climatic history (including at least seven interglacials) and carbon dioxide levels, as measured by the EPICA core from Antarctica (Modified from Siegenthaler et al. 2005, Science 310:1313–1317, Fig. 1. © American Association for the Advancement of Science. Used with permission.)
As Tim Flannery pointed out, ultimately the climate denialists are just a noisy distraction, a rearguard action. They are as irrelevant to the science of climate change as creationists are to the science of evolution. They may make a fuss and have friends in the Republican Party, but the reality of global warming has already convinced the most important audiences: world governments, big businesses, the Pentagon, and other institutions that really do matter. The recent Copenhagen Climate Conference in December 2009 may not have produced as many results as some of us would have liked, or concrete pledges of how much each country would reduce emissions, with enforcement that some were hoping for. Nevertheless, it was a big step from the 1999 Kyoto conference because the United States, China, and India (three of the biggest players in global warming) all agreed to the seriousness of global warming and made some pledges to cut down their greenhouse emissions. A decade earlier, none of these countries agreed to the Kyoto pact.
If data are not convincing enough, and drowning polar bears aren’t convincing, consider this: many normally conservative institutions (oil companies and many other businesses, the military, and insurance companies) are already planning on a world with global warming, even though they often will not admit it to right-wingers. Oil companies are already making inroads into other forms of energy, because oil will run out in a few decades or less and the effects of burning oil will make their business less popular. BP once stood for “British Petroleum,” but now stands for “Beyond Petroleum.” Oil companies may still spend a small percentage of their budget on alternative energy, but they are preparing for a future without oil. Even their publicity people know the public is aware of this problem and the need for alternative energy sources.
Pentagon sources indicate that the military has been making contingency plans for fighting wars in an era of global climate change: what will be the strategic threats when climate change alters the kinds of enemies we might fight and when water becomes scarce. The New York Times (2009) reported in “Climate Change Seen as Threat to U.S. Security” (www.nytimes.com/2009/08/09/science/earth/09climate.html?hp) that in December 2008 the National Defense University outlined plans for military strategy in a greenhouse world. The May 2004 issue of Monthly Review is full of articles about the Pentagon’s plans for climate change. The issue was summarized and analyzed in a Pentagon report An Abrupt Climate Change Scenario and Its Implications for United States National Security, by Peter Schwartz and Doug Randall of the Global Business Network and commissioned by Peter Marshall, director of the Pentagon’s Office of Net Assessment. Their report was released in October 2003 and laid out the grim scenarios that the military must consider in a greenhouse planet. The Pentagon report discusses the likelihood that agricultural decline and extreme weather conditions would overtax energy demand throughout the globe. Rich countries with resources, such as the United States and Australia, might build “defensive fortresses” to keep out hordes of immigrants, while the rest of the world fought over resources. As the report says, “Violence and disruption stemming from the stresses created by abrupt changes in the climate pose a different type of threat to national security than we are accustomed to today. Military confrontation may be triggered by a desperate need for natural resources such as energy, food and water rather than by conflicts over ideology, religion, or national honor. The shifting motivation for confrontation would alter which countries are most vulnerable and the existing warning signs for security threats” (p. 14). To the Pentagon, the big issue is global chaos and the potential for nuclear conflict. The world must “prepare for the inevitable effects of abrupt climate change—which will likely come [the only question is when] regardless of human activity” (New York Times 2009).
Insurance companies have no political axe to grind. If anything, they tend to be on the conservative side. They are simply in the business of assessing risk in a realistic fashion so they can accurately gauge their future insurance policies and what to charge for them. Yet they are all investing heavily in research on the disasters and risks posed by climatic change. In 2005, a study commissioned by the re-insurer Swiss Re said, “Climate change will significantly affect the health of humans and ecosystems and these impacts will have economic consequences” (Epstein and Mills 2005).
Right-wing ideologues may still not like the idea, but big businesses, including oil and insurance, and conservative institutions such as the military, don’t have the luxury of living in an ideological ivory tower. They must plan for the world that will be in the next few decades; however, many symptoms are already apparent. They cannot afford to be caught flat-footed by climatic change when it threatens their survival. Neither can we as a society.
Many of global warming’s effects on the planet are familiar, but let’s get a few things straight. “Global warming” sounds like a good thing to the uninformed. A warmer world seems enticing when many of us shiver through cold winters, but it’s much more complicated than that. Some places on earth will be warmer, but some will be cooler. The net effect is a few degrees warming over the entire planet, which is more than the total temperature change between glacial and interglacial stages during the ice ages. The most severe effects are already perceptible in the polar regions, where both the Arctic and Antarctic ice caps are melting at alarming rates (plate 15). Huge ice shelves the size of several U.S. states break away from Antarctica every few years, a phenomenon that has never been known to occur in human history. The Arctic ice cap is rapidly thinning and breaking up so that, in 2000, the Arctic Ocean at the North Pole was exposed to sunlight for the first time in almost 4 million years since the Arctic first froze over (see chapter 9). My former graduate advisor, the late Dr. Malcolm McKenna, was one of the first humans to see the North Pole covered in water and not ice (plate 15). Now this is an annual occurrence, and scientists are mapping the alarming disappearance of the Arctic ice sheet by satellite. More than 40 percent of the ice cover was lost between 1979 and 2003, and it is almost half gone as I write this. Already there is talk of ships taking the once-legendary “Northwest Passage” through the Canadian Arctic, because the region loses so much ice each year. This may give shippers a shorter route between the Atlantic and Pacific, but it is a serious problem for the rest of us, because an ice-free Arctic has a huge effect on the climate of the rest of the world.
The melting polar ice caps may be bad news for penguins, polar bears, Inuits, and Laplanders, but what about the human population of the world? It turns out that the effects in temperate latitudes are just as scary. More frequent heat waves and droughts, stronger and deadlier hurricanes, and all sorts of unexpected side effects have already occurred and will only worsen, because of global climate change. There are unexpected side effects as well. When the Rocky Mountains were colder with a sharp freeze each winter, the cold snap kept the pine bark beetle populations down. Now these beetles survive winters, and the pine forests of the Rocky Mountains have been devastated. Cold winters keep many diseases in check. Now a host of insect pests and pathogens are spreading new diseases. Cold-intolerant organisms are rapidly moving into higher latitudes because winters do not freeze as they used to. My wife grew up in southeastern Kansas, and at the time, there were no rattlesnakes or armadillos because of cold winters. Now both species are common in the region. This does not begin to address those species dying out because of climate change or how oceans (especially coral reefs) are dying off as they become too warm and too acidic because of excess carbon dioxide that seawater can no longer absorb.
The most serious effect of the last few episodes of greenhouse climate will be sea-level change. High sea levels of the geologic past drowned lower elevations of entire continents (see chapter 9). Currently, sea level is rising about 3–4 mm per year, more than 10 times the rate of 0.1–0.2 mm/year that has occurred over the past 3,000 years (fig. 10.7A). Before that, sea level was virtually unchanged over the past 10,000 years since the present interglacial began. This doesn’t sound like much until you consider that the rate is accelerating and that most scientists predict it will rise 80–130 cm in the twenty-second century. A rise of 1.3 m (almost 4 feet) would drown many of the world’s low-elevation cities, such as Venice, and many countries, such as Bangladesh. A number of tiny island nations such as Vanuatu and the Maldives, which barely stick above the ocean now, are already applying to the United Nations for relief, because they are about to vanish beneath the waves, and their entire population will have to move elsewhere (Environmental News Service, www.ens-newswire.com/ens/dec2005/2005-12-06-02.asp). If sea level rose by just 6 m (20 feet), nearly all the world’s coastal plains and low-lying areas (the Louisiana bayous, Florida, most of the world’s river deltas, the Netherlands, and the rest of Bangladesh) would be inundated. An overwhelming part of the world’s population lives in coastal cities such as New York, Boston, Philadelphia, Baltimore, Washington, D.C., Miami, Shanghai, and London. All of those cities would be under water with just that much additional sea-level rise. If glacial ice caps on Antarctica and the Arctic Ocean melted completely (as they have several times before during greenhouse conditions), sea-level would rise by 65 m (215 feet)! The entire Mississippi Valley would flood, so you could dock your boat in Cairo, Illinois (fig. 10.7B). Such a sea-level rise would drown nearly every coastal region under hundreds of feet of water and inundate New York City, London, and Paris. All that would remain would be the tall landmarks, such as the Empire State Building, Big Ben, and the Eiffel Tower, which would be convenient for tying up boats but not much else.
Fig. 10.7. A, The recent rise in sea level. (Courtesy Globalwarmingart.com; redrawn by Pat Linse) B. If all the glaciers melted, nearly all land below 215 feet in elevation would be drowned, and coastal plains, cities, and harbors would vanish. (From Prothero and Dott 2009; redrawn by Pat Linse)
There’s one other terrifying dimension. As I discussed in chapter 9 of my book Greenhouse of the Dinosaurs (2009), this climatic change may not happen gradually. Studies of ice cores from the Younger Dryas episode, which marked the end of the last ice age and the beginning of the present Holocene interglacial about 11,000 years ago, showed that the switch from glacial to interglacial world did not happen over tens of thousands of years—but flipped wildly from one state to another in less than a decade! This is not the instantaneous event of the hokey Hollywood disaster movie The Day after Tomorrow, but it is much more rapid and catastrophic than anyone had ever thought before these ice cores were studied. Climate change is already more rapid than we have ever seen in the past, and apparently, it can happen even faster. As Richard Alley, an expert on ice-core climatology, wrote in The Two-Mile Time Machine (2000), the rapid switch from interglacial to glacial due to ocean currents “could produce a large event, perhaps almost as large as the Younger Dryas, dropping northern temperatures and spreading droughts far larger than the changes that have affected humans through recorded history, and perhaps speeding warming in the far south. The end of humanity? No. An uncomfortable time for humanity? Yes” (Alley 2000, 184).
During a speech on the Senate floor on July 28, 2003, Oklahoma Senator James Inhofe said, “With all of the hysteria, all of the fear, all of the phony science, could it be that man-made global warming is the greatest hoax ever perpetrated on the American people? It sure sounds like it.” Inhofe needs to look at all the Cretaceous marine rocks in the western part of his state, or the Paleozoic marine rocks in the eastern and central part of his state, to realize that past greenhouse climates have drowned Oklahoma again and again. It would be ironic if someday future residents of Oklahoma, Texas, Arkansas, and Louisiana are sailing around their inundated prairie like Kevin Costner in Waterworld, wondering how someone as dogmatic and misinformed as Inhofe got elected and managed to delay necessary action on global warming for so long.
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