Ruddiman's anthropogenic climate change theory and scientific evidence

Plows, Plagues, and Petroleum: William F. Ruddiman's Evidence for Long-Term Anthropogenic Climate Change

A family huddles together for warmth in a the center of an especially thin-walled thatch hut, the sputtering fire little warmth to combat the wind that finds its cold and hungry way into every possible corner of the one-roomed home. Wrapped in a blanket that is woven of coarse, thick wool if they were lucky, or of a thinner and more permeable fabric if times were harder, these human creatures are forced to wait out the cold winter with little else, hoping that what food they had would be enough to last because more would not be easily forthcoming in the harsh landscape outside. There were neighbors of course, and a lord that ostensibly offered cared for his vassals, but these offered no certain protection against the vagaries of the environment and the potential for destruction that it carried with it at the turn of every season, and especially as the days shortened.

Such scenes were common in the Middle Ages, and it is difficult to imagine that the people of Europe -- the majority of whom lived in huts similar to those described rather than large cities or stone castles as is popularly imagined -- were actually having a significant impact on the global environment when it was so obviously and so extensively having an effect on them. Yet according to the claims and considerable evidence presented by William F. Ruddiman in his book, Plows, Plagues, and Petroleum, this is precisely what was occurring at key times throughout human history, and particularly the development of Western civilization.

Ruddiman makes an excellent case for his assertions, citing an abundance of contemporary scientific and historical evidence in a way that presents a unified and comprehensive view of both the human and the global trajectories over the many millennia of their coexistence. His objectivity despite his obvious convictions is also remarkable, and highly compelling -- Ruddiman is careful to maintain that there is no proven link between his assertion, but that the number of mounting coincidences seems to add up in favor of his ultimate conclusions. Presented in such a manner, it is difficult to disagree with Ruddiman, yet doubt does creep in when some of the scientific objections to his arguments and conclusions are raised by other researchers in the field. This paper will examine Ruddiman's arguments in the context of his status and the opposing views that counter certain specific conclusions Ruddiman draws and his conclusions generally, in an effort to build a more comprehensive and a more compelling understanding of these arguments and their merits.

William F. Ruddiman

Though William F. Ruddiman was quickly drawn to a study of the environment, his initial education did not take place in either atmospheric or environmental sciences. Ruddiman was actually trained as marine geologist. His first major research project, however, involved a study of the migration patterns of sea sediments and their relationship to sea surface temperatures. These in turn have, of course, an effect on -- and are influenced by -- global temperature and climate changes, now a long-standing interest of the author (Ruddiman 2010).

Ruddiman has long been an innovator in the study of global warming, approaching the topic from a multitude of scientific angles and disciplines and always receiving consistent praise for his careful consideration and presentation of evidence, even -- and perhaps especially -- when presented in laymen's terms, as in Plows, Plagues, and Petroleum (Bert 2003). His long-standing respect in the scientific research community is marked both by his current position as a semi-retired professor emeritus at the University of Virginia, and by the prestige of his alma mater, Columbia University (Ruddiman 2010). Ruddiman also has several other published books and numerous articles, and has collaborated with many other researchers in varying fields to develop cutting-edge and comprehensive concepts of what is driving global climate change, and what role human beings might be playing -- and possibly should be playing -- in the global environment (Ruddiman 2010).

Plows, Plagues, and Petroleum

The argument that Ruddiman puts forward in his book is relatively simple and straightforward, even if the evidence behind this argument and the research used to obtain that evidence are not. Essentially, Ruddiman maintains that large changes in the human population and in the degrees and extent of human agriculture, as well as other large-scale human activities as civilization "progressed," have led to periods of global warming and cooling in the past (Ruddiman 2005). Greenhouse gases, though newly a household term, are not new byproducts of human activity, and they were having an effect -- according to Ruddiman -- since civilization began.

Ruddiman begins his argument with the development of agriculture approximately eight thousand years ago, during a time when carbon dioxide and methane in the atmosphere should have been decreasing according to the Earth's natural cycles. Instead, Ruddiman observed an increase of these gases as preserved in ice core samples, and he attributes this to the expansion of human society after the development of agriculture (Ruddiman 2005). Any imaginable combustible fuel, from standard gasoline to cow chips and wood, releases carbon and other greenhouse gases into the air, and the expansion of human populations and the establishment of cities, in Ruddiman's view, necessarily led to greater fuel consumptions and greenhouse gas releases from other human activities (Ruddiman 2005). This is the source of the gas increase observed in the ice core, according to Ruddiman, and evidence of humanity's long-term influence on the environment.

Ruddiman does not leave off here, but travels to the Middle Ages and other periods in the development of human history when less savory things than the agricultural revolution occurred. The bubonic plague, for instance, which wiped out possibly as much as two thirds of Europe's population during the 1300s, coincides with a brief downward "wiggle" in the level of greenhouse gases found in the geological records, a fact which Ruddiman denies is coincidental at all. Instead, according to him, hugely suggests that the massive reduction in human population is tied to the reduction in greenhouse gases present in the atmosphere, for the same reasons that population growth caused an increase (Ruddiman 2005).

Ruddiman concludes his text by examining our current and potentially future state, particularly with our use of petroleum and other fossil fuels. Though many of these actually burn far cleaner than older fuels used in the times Ruddiman discusses, the human population is exponentially larger than it was in the Middle Ages and is still growing, and greenhouse gas emissions are significantly higher now than at any other time in human history. Ruddiman insists that this will lead to a warming trend, and doubts that sufficient technological steps will be taken in the near enough future and on a massive enough scale -- if such a thing were even physically possible -- to alter the situation, especially given the continued use of such fuels (Ruddiman 2005). After making such a compelling argument about long-past events and effects of humanity, Ruddiman's warning strikes especially prepared and well-attuned -- and well-informed -- ears.

Synthesis and Evaluation

It must be acknowledged -- and is, in fact, acknowledged by Ruddiman -- that there is not complete scientific certainty that the current warming trend the Earth is experiencing, if indeed it is experiencing one, is the result of human behavior, and specifically the use of fossil fuels. The evidence that Ruddiman presents in Plows, Plagues, and Petroleum, however, clearly suggests that human beings have the potential to cause worldwide environmental change, and if this potential has existed in the past it must exist a thousand-fold now. Though there are scientific questions and possible problems with Ruddiman's argument, these questions and arguments are no more certain in their conclusions than Ruddiman is with his, leaving it up to each individual to decide what the truth is and ultimately ending in a lot of senselessly heated disagreement rather than rational debate.

What the reality of the situation comes down to is this: there is some evidence that human beings have caused, and are currently causing, changes to global temperatures through the release of greenhouse gases. If human beings truly are causing global warming, action should be taken to keep this from reaching dangerous levels. If this action is taken and human beings were not the cause of the warming, no harm would have been done by moving to more renewable and cleaner energy resources. Whether or not William F. Ruddiman is correct in his assertions, then, we might as well behave as if he is.