Natural forcing from solar and volcanic activity contributes
significantly to climate variability. The post-eruption cooling of
strong volcanic eruptions was hypothesized to have led to
millennial-scale variability in the Glacial and to be weakened in warmer
climate states. The underlying question is whether the climatic response
to natural forcing is state-dependent. Here, we quantify the response to
natural forcing under Last Glacial and Pre-Industrial conditions in an
ensemble of climate model simulations. We evaluate internal and forced
variability on annual to multicentennial scales. The global temperature
response reveals no state dependency. Findings on the ability of models
to simulate past variability could therefore translate to future
climates. Small local differences result mainly from state-dependent sea
ice changes. Variability in forced simulations matches paleoclimate
reconstructions significantly better than in unforced scenarios.
Considering natural forcing is therefore important for model-data
comparison and future projections.