http://www.placergop.org/_content/gw.jpg
I believe Human activity started with agriculture 10,000 yrs ago . The point on the graph where the red turns solid.
William F. Ruddiman1
(1) Department of Environmental Sciences, University of Virginia, Charlottesville, VA, 22904, U.S.A.
Abstract The anthropogenic era is generally thought to have begun 150 to 200 years ago, when the industrial revolution began producing CO2 andCH4 at rates sufficient to alter their compositions in the atmosphere. A different hypothesis is posed here: anthropogenic emissions of these gases first altered atmospheric concentrations thousands of years ago. This hypothesis is based on three arguments. (1) Cyclic variations in CO2 andCH4 driven by Earth-orbital changes during the last 350,000 years predict decreases throughout the Holocene, but the CO2 trend began ananomalous increase 8000 years ago, and the CH4 trend did so 5000 years ago.(2) Published explanations for these mid- to late-Holocene gas increases basedon natural forcing can be rejected based on paleoclimatic evidence. (3) A wide array of archeological, cultural, historical and geologic evidence points to viable explanations tied to anthropogenic changes resulting from early agriculture in Eurasia, including the start of forest clearance by 8000 years ago and of rice irrigation by 5000 years ago. In recent millennia, the estimated warming caused by these early gas emissions reached a global-mean value of 0.8 °C and roughly 2 °C at high latitudes, large enough to have stopped a glaciation of northeastern Canada predicted by two kinds of climatic models. CO2 oscillations of 10 ppm in the last 1000 years are toolarge to be explained by external (solar-volcanic) forcing, but they can be explained by outbreaks of bubonic plague that caused historically documented farm abandonment in western Eurasia. Forest regrowth on abandoned farms sequestered enough carbon to account for the observed CO2decreases. Plague-driven CO2 changes were also a significant causal factor in temperature changes during the Little Ice Age (1300–1900 AD).
SpringerLink - Journal Article
And I also feel compelled to post this paper ,But You are Right SoilWatcher, this contention is for another thread.
If any field of endeavor Deserved a BIG TENT it is TP. The bigger the tent the better, it is the ultimate of a conservative cause and a tree hugging earth mother cause. Let every group political or scientific express their interest in TP the way they can. The local garden club to organic farmers to show off the horticultural gains, the environmental engineers and the fossil fuel chemical engineers............this list just goes on and on..........even the "fringe" or "new age" can play their part.
Erich
