  We propose a conceptual model which generates abrupt climate changes akin to
Dansgaard-Oeschger events. In the model these abrupt climate changes are not
triggered by external perturbations but rather emerge in a dynamic
self-consistent model through complex interactions of the ocean, the atmosphere
and an intermittent process. The abrupt climate changes are caused in our model
by intermittencies in the sea-ice cover. The ocean is represented by a Stommel
two-box model, the atmosphere by a Lorenz-84 model and the sea-ice cover by a
deterministic approximation of correlated additive and multiplicative noise
(CAM) process. The key dynamical ingredients of the model are given by
stochastic limits of deterministic multi-scale systems and recent results in
deterministic homogenisation theory. The deterministic model reproduces
statistical features of actual ice-core data such as non-Gaussian
$\alpha$-stable behaviour. The proposed mechanism for abrupt millenial-scale
climate change only relies on the existence of a quantity, which exhibits
intermittent dynamics on an intermediate time scale. We consider as a
particular mechanism intermittent sea-ice cover where the intermittency is
generated by emergent atmospheric noise. However, other mechanisms such as
freshwater influxes may also be formulated within the proposed framework.
