William Ruddiman has been a scientist of climate (see http://www.evsc.virginia.edu/faculty/ruddiman-william-f/) over most of the recent span of a tremendous growth in the study of that subject, a growth that continues a two-century surge in earth/life sciences, marked by the work of Hutton, Darwin, Wegener, as well as in the study of humanity's story. His most recent effort -- which I am attempting to extract from here (and any re-statings and errors in this entry are, be assured, mine) -- resulted in Plows, Plagues, and Petroleum: How Humans Took Control of Climate (Princeton 2005). His work does not directly deal with the Grand Canyon, of course, yet his thesis is an important element in understanding the Canyon's human context, its politics. His thesis also impacts heavily on the idea of wilderness and what it can mean if we properly comprehend humanity's history.
Briefly stated, Ruddiman argues that human activities arising from the Neolithic Revolution have already had the not-to-be-understated result of preventing the start of a period of increasing glaciation. To show this, he summarizes the current picture of ice ages, emphasizing their periodicity. That periodicity indicated that a glacial was due and yet is not happening. In investigating why, he could find no convincing natural cause, and so studied human activities that might have increased the greenhouse gases of carbon dioxide and methane over the relevant period of the past 10+ millennia.