He describes how wild grains and animals were domesticated, as well as the new technologies that made farming possible (sickles, baskets, pestles, gourds, irrigation, the wheel, the plow). He uses a chart to plot these movements. His evidence is mainly archeological, historical, and botanical with heavy doses of appeal to imaginary scenarios. Its power to convince is narrational. His ultimate point in cataloguing this change is to assert how, for first time in history, humans become a prime factor in altering earth's natural landscapes. Land was now exploited and degraded through deforestation for crops and soil erosion.
Summary: Ruddiman summarizes the history of how humans began to shape the earth through technology and landscape transformation. He relies on the credibility of his narrative.
Ch. 8, pp. 76-83: His main claim is that humans rather than nature have created a rise in atmospheric methane. He presents several lines of argument, beginning with his own explanation of the problem. The anomalous rise in methane cannot be accounted for by natural law since in his detailed investigations tropical and boreal wetlands have shrunk and have not emitted more methane than expected. Citing his own and others' research, he claims the new source generating methane is human farming through such methods as diversion of rivers to irrigate rice (artificially created wetlands), biomass burning (slash-and-burn), livestock emissions, and increased human waste from increased population. Of these, the major factor is irrigation. His main evidence is a correlation between the rise of irrigation use in Southeast Asia (and rise in population) and the methane data burst before industrialization. When his calculating model seems ready to fail, he switches to asserting authority rather than evidence to claim that rice farming was inefficient (more weeds in flooded areas) which meant methane was emitted in excess of the proportion of human population. Realizing how little his opinion is based on facts, he calls for more quantitative evidence, while insisting that the point will be hard to prove. His rhetoric is based on his authority and the weak correlation he draws.
Summary: Ruddiman's point is to try to show how methane gas increases before the industrial era stem from the anthropogenic effects of agriculture, particularly irrigation methods.
Ch. 9, pp. 84-94: The principal claim in this chapter is that deforestation is to blame for pre-industrial increases in atmospheric CO2. First he establishes that CO2 has increased and that it cannot be explained naturally. Claiming lack of expertise, he assesses research into CO2 levels in the ocean that shows the cyclical pattern of climate-based increase and decrease in CO2. Yet he finds the current cycle is different. Taking data from a "high resolution CO2 record spanning the last 11,000 years," he sees levels increasing where they should naturally be dropping. He invokes two natural explanations, discusses only one of them (that extra CO2 came from the natural release of carbon), and dismisses by authority the effort to find natural explanations since all the major climate system factors in the past (radiation, ice sheet retreat, rise in sea level, vegetation change) behaved in same way through the last four intervals of ice melting, yet only the current one shows CO2 rises in the interglacial period. He spends the last part of the chapter explaining a formula, based on William the Conqueror's Domesday Survey in 1089 and scientific evidence of past clear cutting (pollen in sediment, charcoal in soil), to estimate quantitatively whether thousands of years of deforestation could have released the immense amounts of gas necessary to explain CO2 levels. He concludes based on his formula and the data that massive deforestation and burning caused pre-industrial rises in carbon dioxide levels. He ends with an imaginative appeal to seeing a hillside with tamed goats as a natural forest.
Summary: This chapter gives his rational reasons for believing that widespread deforestation could lead to rise in greenhouse gases in the last thousands of years of human civilization.
Ch. 10, pp. 95-105: The main claim in this chapter is that the human-induced increase in greenhouse-gases has delayed the onset of natural glaciation. Global cooling trends (retreat of forests and increase in tundra and sea ice) driven by natural orbital variations has masked global warming in the last 8,000 years. Ruddiman uses William's climate-modeling analysis to show that without this global warming, parts of earth's terrain would be glaciated. His conclusion is that human-based carbon emission has caused higher temperatures that have stalled the natural cooling process. This argument is based on modeled data, scientific theory, and his own view that natural processes cannot explain the change. Then he shifts into a discussion based on his authority of his own simulation of how much cooler the earth would be today without human greenhouse gases. His results are inconclusive.
Summary: This chapter adds further basis for Ruddiman's view of human change of climate through the rhetoric of scientific findings combined with his own interpretations of them.
Ch. 11, pp. 106-114: His claim is that major challenges to his theory do not invalidate it. One challenge called him to look farther back in the sequence of ice-age cycles, which led to him review the ice core data. His review and charts of the new evidence confirm, in his view, the predictive power of his position, although it contradicts the idea that current glaciations is overdue. He finds uncertain additional information that Antarctic temperatures had plummeted to glacial conditions despite the longer interglaciation period, and concludes from reason (not evidence) that the former interglaciation period must have started far earlier than the present one. A second challenge is that ocean warmth means that ice sheets are decreasing, not growing as projected. He rejects this from his own previous studies that say as ice sheets are growing the ocean can stay warm ("lagging ocean warmth") although he admits the reasons for this are unclear. He rejects also the notion that humans could not have slash and burned enough forest to cause such huge gas rises, appealing to his own model in which the prevention of a natural drop in CO2 levels is taken into account to fill the gap. His conclusion is that these challenges do not disprove his thesis. At the end his adds a first person discussion of the way university pressures prevent real reflection and how much time it takes for scientific revolutions to occur -- an appeal from pathos for the reader's patience despite the lack of forthcoming solid evidence. The persuasive effect of this chapter is that it shows the author to be open to responding to criticism, but it does not eliminate the suspicion that he interprets data in the direction of his theory.
Summary: Ruddiman takes on several challenges to his theory and attempts primarily through reason and less through scientific evidence to show how the criticisms are inadequate.
Ch. 12, pp. 119-126: Ruddiman's main claim is that the oscillations (dips) in CO2 levels during the Middle Ages can be explained through natural temporary (not gradual orbit-based) climate variations. He appeals to an analogy of a heating cycle broken by a sudden storm and to imagination of how glaciers would have affected farming. Then he shifts from narrative examples to looks at the natural archives -- tree rings, mountain ice, and coral -- for evidence that a little ice age occurred. He explains the process by which northern regions are cooled through 11-year cycles of variations in sunspots (using satellite and telescope measurements) and how volcanic eruptions cause a cooling effect (sulfuric acid in vapor reflects radiation). He casts doubt on conventional chemical explanations for CO2 drops when it is cooler, saying the models do not explain the rapidity of value drops during stable climate.
Summary: Ruddiman writes this chapter to eliminate the criticism that an ice age appearing in recent history contradicts his view that the globe is warming. His appeal is based on natural cycles and events, and an assertion of his own authority.
Ch. 13, pp. 127-138: This chapter claims that drops in CO2 levels correlate with the human history of disease (pandemics). After claiming no historical expertise, he culls evidence (without citations) from a historical narrative that is presumed to be universally acceptable. He finds no evidence in the historical record (examples) that either war or famine (regressions from agricultural progress) could be responsible for elevated CO2 levels. He plots preindustrial pandemics on a chart with population losses, and compares these with dips in CO2. His conclusion is that there must be a correlation, though not yet causality, between pandemics and dips in atmospheric CO2. The argument rests on the rational premise of a correlation between human history and scientific data.
Summary: This chapter leads into his more detailed discussion of the effects of disease in terms of creating greenhouse gases. It is introductory and based on an inexpert field of…