Last month, both the Pentagon  and the Intergovernmental Panel on Climate Change  of the United Nations issued projections of the long-term impact of hydrocarbon emissions. They could "slow down economic growth, make poverty reduction more difficult, further erode food security, and prolong existing and create new poverty traps, the latter particularly in urban areas and emerging hot spots of hunger.”
That was the wording of the U.N. report, but the Pentagon sounded much the same, warning that climate change "will influence resource competition while placing additional burdens on economies, societies, and governance institutions around the world." The U.S. military characterizes these tendencies as "threat multipliers that will aggravate stressors abroad such as poverty, environmental degradation, political instability, and social tensions – conditions that can enable terrorist activity and other forms of violence."
Isn't such talk rather alarmist, considering all the research by scientists who reject the idea of anthropogenic global warming? Consider a recent survey  of the literature appearing in scientific journals between 1991 and 2012. By my calculation, scientists rejecting the man-made climate change published an impressive 0.17 percent of peer-reviewed papers containing the phrases "global warming" or "global climate change." That's almost one-fifth of one percent!
Clearly the debate is far from over. But a couple of weeks back, an assistant professor of philosophy at Rochester Institute of Technology named Lawrence Torcello argued, in a much-discussed article , that we have "good reason to consider the funding of climate denial to be criminally and morally negligent." His comments inspired an enormous amount of hate mail , including a number of threats of violence. Many of his correspondents were so outraged that they could not bring themselves actually to read the article, relying instead on second- and thirdhand accounts of Torcello's argument that refuted, not what he wrote, but what he could almost certainly be imagined to have intended to say.
Lest anyone feel too sympathetic to Torcello, I must point out that he failed to consider other explanations for why 99.83 percent of the scientific papers discussing climate change assessed it to be a real problem. It is possible, for example, that the researchers who wrote them were funded by the dirty tree-hugging hippies running the Pentagon.
Now, irony regarding any topic that elicits hate mail seldom turns out well. The people you don't anger, you tend to confuse. But it proves almost irresistibly tempting once a debate has reached a standoff. Pieces remain in play on the chess board but neither side makes any progress. That's where things stand now. More than two-thirds of the American public thinks that global warming is real despite the fact that it still gets cold in winter, just as they believe the earth to be spherical even though the front yard is, plainly, flat. Many will stick to those opinions, no matter how well-funded the denialists may be. (There's just no reasoning with some people.)
The more substantial discussion now seems to focus on the processes of climate change -- about whether, say, the continued melting of polar ice will trigger the release of enormous amounts of methane into the atmosphere. If so, how soon? And how fast, once it starts?
The particular mechanisms involved in climate change don't much interest Paul R. Ehrlich and Michael Charles Tobias in their book Hope on Earth: A Conversation, from University of Chicago Press . Ehrlich, the senior author, is a professor of population studies at Stanford University, where he is also president of the Center for Conservation Biology; Tobias is a writer and and documentary director primarily interested in environmental issues. But the question of the tempo of ecological disaster hovers over the discussion as a whole.
Ehrlich's The Population Bomb (1968) became one of the most ubiquitous of alarming paperbacks during the 1970s. It was the neo-Malthussian equivalent of one of Hal Lindsay's books about the End Times; extrapolating from birth rates and the rate of growth of food supplies, it projected worldwide famine and social collapse by about 1980. The promotional copy for Hope on Earth identifies Ehrlich as one of "the world's leading interdisciplinary environmental scientists," and undoubtedly he does remain one of the best =-known. But it is important to keep in mind that some ecologists were sharply critical of The Population Bomb even at the height of its popularity, seeing it as reductive and alarmist. Ehrlich overemphasized the environmental impact of poor countries while underemphasizing that of pollution and wastefulness in the consumerist societies. He also failed to grasp either the increased agricultural output that came with the Green Revolution or the environmental impact of the pesticides making it possible.
Ehrlich ventures no such prognostication in his dialogue with Tobias, conducted over a couple of days at the Rocky Mountain Biological Laboratory in Colorado. As far as I can determine, the exchange took place during 2011, with revisions and elaborations of the transcript from both parties continuing over the following year. In spite of the protracted effort, it remains very much a conversation, for good and for ill. It roams without a map or a set agenda, however provisional, and the speakers are prone to data-dump monologues whose pertinence is not always obvious.
The conversation can be interesting when Ehrlich and Tobias butt heads. They approach environmental matters in distinct and sometimes conflicting perspectives. Tobias seems exemplary of a generation of environmentalists who emerged in Ehrlich's wake -- one for which preserving biodiversity and the wilderness are concerns inseparable from the defense of animal rights, as well as an attachment to ascetic mysticism. (He's reminiscent of the "level 5 vegan" who appears in one episode of "The Simpsons": "I won't eat anything that casts a shadow.") By contrast, Ehrlich clings fast to both a secular worldview and a belief that overpopulation, as such, is a major driving factor in ecological problems. He enjoys the comforts and conveniences available in advanced industrial society and can eat a chicken sandwich with few, if any, moral qualms. "The thing I hate about vegetarians," he says, "is that they're not put off by the screaming of cabbage."
One substantial issue sometimes emerges from their bull session, only to sink back out of view again. It could be called the problem of ecological triage: of how to decide what can be saved and what can't, and on what basis such judgments can be made.
"One of the troubles," says Ehrlich, "is that there are far too limited funds going into trying to save our life-support systems. It's a big allocation issue, how much to spend on description and cataloging and protecting species, as opposed to focusing on populations and the ecosystem services they provide…. Is it more important, for instance, to maintain pest control services in the grain baskets of the world or to protect narrow endemic species in tropical hotspots? Not an easy question to answer, and one with ethical implications."
And one that will come to the fore more and more over the next few decades, if the effects of climate change are felt on anything like the scale that scientists are discussing. Tobias characterizes it -- more generally, if also with more wool -- as the problem of "ascertaining those points of convergence wherein there are thematic flash points, positive pathways that the majority of scientists and people in general can agree upon in an effort to improve the conditions of life on Earth -- both for our species and others."
By "points of convergence" and "thematic flash points," he seems to mean whatever minimal bases of agreement about core values and priorities can serve as a basis for deciding how many arks can be built, and who gets a compartment. The upshot of Ehrlich and Tobias's discussion -- if not their actual conclusion, since they seem not to reach one -- is that no such basis can be identified at present. The effects of climate change may become severe within a couple of decades. The authors probably meant their title to be encouraging, but irony seems to have prevailed, because Hope on Earth offers precious little of it.