Plows, Plagues and Petroleum
Plows, Plagues and Petroleum: How Humans Took Control of Climate is a 2005 book published by Princeton University Press and written by William Ruddiman, a paleoclimatologist and Professor Emeritus at the University of Virginia. He has authored and co-authored several books and academic papers on the subject of climate change. Scientists often refer to this period as the "Anthropocene" and define it as the era in which humans first began to alter the earth's climate and ecosystems. Ruddiman contends that human induced climate change began as a result of the advent of agriculture thousands of years ago and resulted in warmer temperatures that could have possibly averted another ice age; this is the early anthropocene hypothesis. Synopsis Ruddiman begins the book with a brief introduction to the science of climate change and the various individuals that have been key in influencing the field over the years. He also notes that the earth's climate has been drifting toward cooler temperatures for the last 55 million years. The dominant hypothesis for this trend is that large volcanic eruptions have subsided while increasing amounts of carbon dioxide have been absorbed out of the atmosphere due to interactions between monsoon rains and ground up rock exposed by India pushing into Asia and creating the Himalayas. Additionally it is believed that the melting ice that produced higher sea levels resulted in the ocean absorbing more carbon dioxide out of the atmosphere. These two natural occurrences resulted in less carbon dioxide in the atmosphere hence possibly producing the general cooling trend. According to Ruddiman, beginning about 900,000 years ago the earth has begun to go through regular glacial cycles in which glaciers or ice have covered approximately one quarter of the earth's total surface. These conditions typically last for about 100,000 years and are followed by brief interglacial periods of more temperate weather. Ruddiman cites various researchers in geology and astronomy who pioneered the understanding of earth's climate as a function of its orbit. The various cycles of earth's climate seem to be explained by the eccentricity, axial tilt, and precession of the Earth's orbit as well as cycles in the amount of solar radiation. Ruddiman primarily relies on the groundwork by Milutin Milankovitch to explain the effects of solar radiation and earth's orbit on the climate. By examining ice cores from around the world scientists have been able to link levels of greenhouse gases such as carbon dioxide and methane to the various cycles of earth's climate history. The discovery of carbon dating aided a great deal in developing this understanding. Upon investigating the levels of carbon dioxide and methane in the earth's atmosphere in the most recent interglacial period—10,000 years ago—Ruddiman noticed that levels of carbon dioxide and methane were steadily rising despite the fact that the earth's natural cycles determined that they should have been decreasing. It was this discovery that lead to Ruddiman's search for an explanation and ultimately the creation of this book. Ruddiman's central argument is that this most recent