In the scheme of things that really matter—those with dramatic and potentially life-altering consequences—surely the prospect of global climate change must rank high, perhaps even highest. Yet it is clearly a human trait—shared with frogs, as Al Gore likes to point out in his lectures—to put out of mind what is unlikely to affect one’s quality of life over an insensibly short period of time.

As I write this book review, the U.S. Supreme Court has just taken up for the first time an issue directly involving global warming. Twelve states, joined by the District of Columbia, are demanding that the Environmental Protection Agency (EPA) regulate, in accordance with their mandated authority, carbon dioxide (CO2) pollution from motor vehicles. For anyone wondering why the EPA would decline to regulate CO2 pollution, Deputy Solicitor General Gregory Garre, representing the federal government, explained that “now is not the time to exercise such authority in light of the substantial scientific uncertainty surrounding global climate change…” Uncertainty? On page 260 of his book, Mr. Gore reproduces in 1.5 cm-high letters the judgment of Donald Kennedy, Editor in Chief of Science Magazine that “Consensus as strong as the one that has developed around this topic [global warming] is rare in science.” On the next page, the reader will see the number 928 in numerals 2-cm high; this is the size of a random sample of peer-reviewed articles dealing with climate change published in scientific journals during the period 1993-2003. Under 928 is an equally large 0%: the percentage of those articles in doubt as to the cause of global warming. I will return to this point shortly.

“Uncertainty” aside, the plaintiffs still face a steep hurdle. “You have to show the harm is imminent,” Justice Scalia instructed Assistant Attorney General James Milkey of Massachusetts, who represented the plaintiffs; “I mean, when is the cataclysm?” “The harm,” Milkey explained, “does not suddenly spring up in the year 2100; it plays out continuously over time. Once these gases are emitted…the laws of physics take over.” The dialogue continued. Justice Scalia eventually acknowledged the role of carbon dioxide as a pollutant in the “stratosphere”. “Respectfully, Your Honor,” Milkey pointed out, “it is not the stratosphere. It’s the troposphere.”—to which Scalia replied with surprising frankness: “Troposphere, whatever. I told you before I’m not a scientist. That’s why I don’t want to have to deal with global warming, to tell you the truth.”

At this point in the news report I was hearing on the radio, I willingly would have sent a copy of An Inconvenient Truth to Garre and Scalia at my own expense if I thought that act of generosity would do any good. Most likely, it wouldn’t, for, as Upton Sinclair wrote—and Al Gore reproduces on page 266—“It is difficult to get a man to understand something when his salary depends upon his not understanding it.” And, I would add, not just salary, but his (or her) investment portfolio, stockholders, capital equipment maintenance and replacement, market control, political constituency and electability or appointability to public office as well.

Author and former U.S. Vice President Al Gore does not need an introduction. Nor by now is the existence of his book likely to be unknown to physicists. And yet, surprisingly, I have found that relatively few physicists or other scientists of my acquaintance have actually read it. The legalistic exchanges cited above provide a compelling reason for reviewing An Inconvenient Truth in a physics journal concerned with scientific history, culture, and education.

If someone presumably as educated as a US solicitor general or a justice on the US Supreme Court can reflect such ignorance of the evidence underlying the broad consensus among scientists that rapid global climate change is occurring as a result of anthropogenic release of greenhouse gases into the atmosphere, then it is reasonable to suppose that scientific ignorance of this magnitude is pervasive among the general population. And how could it be otherwise? Return to page 262 with the 2-cm high 0% (of scientific articles in doubt of human-caused global warming) and fold out the adjoining page to find the following equally large numerical figures: 636 articles in a random sample of articles in the popular press discussing global warming during the previous 14 years; of these, 53% express doubt as to the cause. Clearly, there is a chasm-wide divide between what scientists report in the peer-reviewed scientific literature and what laymen read or hear in the general news media. In my opinion, An Inconvenient Truth can be a valuable source of information for scientists who would like to help reduce that divide.

As a physicist and chemist who investigates aspects of global climate change myself, and who has lectured on the subject for over 15 years, I have read much of the recent literature, both scientific and popular, and am reasonably familiar with many of the physical and chemical issues, the broad brush strokes of scientific consensus as well as the fine points of scientific contention. Frankly, much of the original literature, however important for its content, makes for dull reading. The onerous task of wading through turgid scientific prose is compounded in many cases by the difficulty of extracting critical information from a tangle of plots of different physical quantities all on one graph with multiple axes and different scales and units. It verges on hopelessness to display these data, as scientists have published them, in public or even university lectures, to convey to an audience the serious consequences the findings portend.

In contrast, An Inconvenient Truth is remarkable for its comprehensible, inclusive, and accurate presentation of evidence for global warming—all the more so as the author is not a scientist. Virtually all the seminal issues are addressed in the book: atmospheric accumulation of carbon dioxide and methane and the connection between greenhouse gases and temperature; the melting of glaciers, ice shelves, and continental ice and consequent sea-level rise; melting of the permafrost; the paleoclimatic evidence from Antarctic and Greenland ice cores as deduced from dust, pollen, and fractionation of hydrogen and oxygen isotopes as proxies for temperature; the abundance and isotopic composition of foraminifera from sea-bed sediments; effects of temperature rise and seasonal shifts on migrations and food supplies of birds and insects; the linkage between rising sea temperatures and the intensity of cyclonic weather events; the planetary climate as a nonlinear system subject to amplifying feedback effects and abrupt transitions between vastly different equilibrium states, such as may apply to the thermohaline circulation in the Atlantic—and much more.

As remarkable as the inclusive content, is the visually attractive mode of presentation. There are no equations in the book, which in this case is a virtue. Instead, concise written descriptions in large font sizes to facilitate reading and to accentuate points of major significance, accompanied by colorful, readily comprehensible diagrams and photographs and fold-out pages, bring out each essential issue under discussion with unmistakable clarity. This is a book to fascinate the eye, as well as inform the brain. In an age when many Americans (including physicists) are more likely to get their information from some visual medium like television or the internet, the essential content of An Inconvenient Truth will remain in the mind of a reader far longer than the technical details of a standard text or any other book on climate change for the general reader that I have yet seen. Beyond the classroom, Gore’s book would serve ideally to provide useful explanations, charts, graphs, photographs, and references to physicists who are not specialists in the subject of climate change, but who wish to help dispel some of the false information spread widely by global warming deniers via the internet and print news media, and by oil and power companies through “educational materials” furnished to local schools (see L. David, “Science a la Joe Camel”, Washington Post, 26 November 2006, p. B01) or to special interest groups (see C. Mooney, “Some Like It Hot”, www.motherjones.com).

Besides the scientific content of the book, there are personal reflections by the author about occurrences in his life. I mention this only so that a prospective reader will know they are there, but my concern in this review is exclusively with its scientific content and educational potential. Because of the latter, I recommend the book to physicists for their personal reading and civic applications. Regrettably, the book does not have a table of contents or an index or a standard bibliography (although sources of information are credited), which makes retrieving information more time-consuming than it need be. My own inelegant solution to the problem was to use an ample supply of “Post-It” tabs. The book concludes with two useful summaries printed together on the same pages: an itemization of what the reader can do personally to help reduce emissions of greenhouse gases and a concise debunking of ten of the most frequently encountered misconceptions about global climate change.

An Inconvenient Truth is not the only recent book for a nonspecialist reader that addresses global warming, but the organization and format of the book makes it particularly suitable for hesitant physicists whose expertise may lie in some distant domain to develop confidence to address this serious issue with townspeople in their local communities. While preparing this review, I was asked by a physicist colleague to whom I pointed out that positive feature, “why should physicists whose expertise lies elsewhere be particularly qualified to educate the public about global warming?” The short reply is simply, if they don’t, who will? In face of executive*, legislative, and judicial branches of a federal government, and powerful, well-financed corporate self-interest groups, that give every impression of being opposed to, or skeptical of, the incontrovertible evidence of a human-caused global climate problem, the “first, last, and only line of defense against”…well, quite literally,…”the scum of the universe” [No, here that line from the Men In Black song refers to greenhouse gases, not to space aliens or global warming deniers] is the nation’s well-informed and environmentally conscious core of scientists, especially physicists. Training in physics should signify the capacity to evaluate scientific evidence, reach valid scientific conclusions, and explain esoteric points of science to laymen. The facts that substantiate anthropogenic causes of global warming are physical in nature, and physicists, irrespective of specialization, should be able to acquire sufficient background to understand them. An Inconvenient Truth is a particularly suitable reference to begin with.

Nevertheless, despite an overall favorable impression upon reading the book, I could not dispel a feeling of disappointment in the author’s facile conclusion that everything will go well (“the future is ours”) if only we choose to use “our democracy and God-given ability to reason…and make moral choices”. Perhaps one expects such saccharine words from a politician, even a scientifically well-informed one, because no politician gets elected by alienating voters. However, the full truth is more inconvenient than the author either realizes or chooses to acknowledge. I am a physicist with no political ambitions at all, and my own public lectures on global climate change conclude differently from his. They point out that there is in fact only one fundamental cause of a global-warming problem—by which I mean the unnatural variation in global climate—and that cause is the uncontrolled growth in human population. The more people there are on the planet, the greater is their demand for resources and the greater is the resulting environmental degradation, waste, and pollution. The most telling graph in Gore’s entire book—a graph similar to those I have displayed in my classes and public lectures for nearly two decades—is the plot that spans pages 216 and 217. On page 216 the number of humans on Earth remains flat below 250 million for more than 160,000 years. On page 217 it skyrockets to 6 billion people primarily over the past 60 years and is expected to reach 9 billion by 2050. Gore takes comfort in thinking that the rate of growth is slowing, but the actual number of people is still increasing—and that is what matters because the number of people determines the demand for energy, which ultimately creates the global-warming problem.

So long as most people on the planet (including well over 60% of the US population, according to recent polls) hold supernatural beliefs regarding the primacy of human beings and the sacredness of human life, so long as rampant population growth occurs in those parts of the world where misogynistic theocracies and other dysfunctional cultures treat women like chattel, it is doubtful whether the “God-given ability to reason”, to which the author refers, will ever recognize a growing human population as a cancer on the planet, occupying all living space, devouring all resources, and fouling all habitats. Or whether the “moral choices” to which the author refers will ever include stringent restrictions on human reproduction.

From the standpoint of physics, not politics, there is one basic “truth” upon which any effective solution to the global-warming problem must rest, and it is this: Nothing is exempt from the laws of physics. This means that continuous growth on a finite planet is not sustainable; that sound science, not market forces, should determine national policy; and that there is a price to be paid for environmental degradation.

And one thing more. On page 299 of his book, Gore reproduces the photograph of the Earth that a robotic spacecraft took years ago as it was leaving the solar system. At that distance, the entire planet appeared as a single blue pixel. Gore rightly points out that “It is our only home. And that is what is at stake.” But it also needs to be said that that blue pixel is of no cosmic significance whatever. If it vanished this instant, nothing else in the universe would mourn the loss. Far from being the pinnacle of a special creation, we humans are but one of many kinds of organisms that evolved to share the living space on a fragile and finite planet among countless other suns and planets. Nothing “out there” is looking after our well-being; for that we must rely on our own good judgment. And if, through carelessness, greed, and stupidity, humans damage beyond the tipping point the one place in the cosmos where they evolved and can live, then, like any other unfit species, they will go extinct. That is the inconvenient truth.