Ice core data - Ice Ages and Interglacials: Measurements, Interpretation, and Models - page 166

mechanisms, involving changes in ocean circulation, in atmospheric concentrations
of greenhouse gases or haze particles, and in snow and ice cover, have been
invoked to explain these sudden regional and global transitions. We do not know
whether such changes could occur in the near future as a result of human effects
on climate. Phenomena such as the Younger Dryas and Heinrich events might
only occur in a glacial world with much larger ice sheets and more extensive sea
ice cover. All the evidence indicates that most long-term climate changes occur in
relatively sudden jumps, rather than as incremental changes (Adams et al., 1999).
More recently, there have been smaller climate variations such as the Medieval
Warm Period and Little Ice Age (see Figure 4.2 ).
A topic of considerable concern today for the climate in the near future is the
question of how stable the climate was in past interglacial periods. The climate
during the Holocene has been very stable, as Figure 4.3 demonstrates. However,
Figure 4.7 shows that large variations in climate apparently occurred during the
Eemian interglacial period and it is not clear how the Eemian interglacial differed
from the Holocene.