The idea of the Anthropocene

Crutzen and Stoermer (2001) have proposed that the period from the late eighteenth century onwards merits separate designation as the Anthropocene. Their suggestion arises from .an acknowledgement of the increasing role of human activities in the functioning of the Earth system, as witnessed by, for example:

• The accelerated use of fossil-fuel resources, bringing with it steeply rising emissions and an unprecedented gradient of change in atmospheric CO2 concentrations.

• The impact of human activities on other key global biogeochemical cycles, including nitrogen.

• Major changes in the Earth's surface cover as a result of processes such as deforestation, land reclamation, irrigation and soil degradation induced by human activities.

Irrespective of doubts about the choice of a starting date (Ruddiman, 2003b; Steffen and Crutzen, 2003) and of the extent to which the concept of the Anthropocene will be justified as the long-term future unfolds, the term helps to capture and dramatise the idea that, as Steffen et al. (2004) state: ‘The Earth is currently operating in a no-analogue state. In terms of key environmental parameters, the Earth System has recently moved well outside the range of the natural variability exhibited over at least the last half million years. The nature of changes now occurring simultaneously in the Earth System, their magnitudes and rates of change are unprecedented.’

Figure 8.1 shows graphically some of the key indicators of the current no-analogue state as they have evolved over the last three centuries.