  Climate variability over the past million years shows a strong
glacial-interglacial cycle of ~100,000 years as a combined result of
Milankovitch orbital forcing and climatic resonance. It has been suggested that
anthropogenic contributions to radiative forcing may extend the length of the
present interglacial, but the effects of anthropogenic forcing on the
periodicity of glacial-interglacial cycles has received little attention. Here
I demonstrate that moderate anthropogenic forcing can act to damp this 100,000
year cycle and reduce climate variability from orbital forcing. Future changes
in solar insolation alone will continue to drive a 100,000 year climate cycle
over the next million years, but the presence of anthropogenic warming can
force the climate into an ice-free state that only weakly responds to orbital
forcing. Sufficiently strong anthropogenic forcing that eliminates the
glacial-interglacial cycle may serve as an indication of an epoch transition
from the Pleistocene to the Anthropocene.
