Among scientists, there is now serious talk that the Holocene has ended and a new era has begun, called the Anthropocene, a term first used in 2000 by Paul Crutzen, who shared a Nobel Prize for his work on the chemical mechanisms that affect the ozone layer.In that regard, I submit these figures that I use in talks on my research on nitrate reductase in bacteria:
Those of us alive today may well be able to say we were present when the Anthropocene epoch was formally adopted. But we will not be able to say we were present at the start of the Anthropocene. There is a strong case that the Anthropocene begins with the Industrial Revolution, around 1800, when we began to exert our most profound impact on the world, especially by altering the carbon content of the atmosphere.
Clearly the rise begins at around year 1800. Here is atmospheric concentration (left axis) and radiative forcing (right axis) of methane, which is a potent green house gas, about a third as bad as carbon dioxide. Nitrous oxide, which is in part produced by bacteria in agricultural soils, is even less potent, at about a tenth the radiative forcing of carbon dioxide. But the point is that all three gases closely mirror the human population growth.
From IPCC 2007 Synthesis Report (the x-axis is identical to the human growth curve, starting at 1000 and ending at 2000.)