Globally consistent natural evidence on past climate evolution is
indispensable for climate model evaluations and forecasts. However, it
has rarely been investigated quantitatively whether large sets of
globally distributed pollen records with limited dating resolution can
be statistically linked. This could facilitate the identification of
global in contrast to regional climate change signals on millennial to
orbital time scales. We consider a global set of time-irregular pollen
records for a joint analysis of spatial similarity on different time
scales during the last glacial. Making use of measures suitable for
irregular time series and by application of a spatio-temporal stochastic
model, we examine significant commonality between pollen records. We
quantitatively assess the resulting paleo-climate networks while
respecting the spatially heterogeneous and sparse proxy archive layout.
The network configurations are compared to synthetic proxy networks,
which mimic different real-world record impairments. We find strong
commonalities of well resolved Chilean, North Pacific and European
records on orbital to millennial time scales. They reveal partly
inverted deglaciation signals for westward exposed coastal tree
vegetation. Such signals are consistently observable for several
mid-latitude records, probably indicating equatorward shifts of westerly
circulation structures during the last glacial. Surrogate data suggests
that a notable part of total records might be insufficiently resolved to
detect statistically significant record similarity at least when
classical correlation-based measures are utilised. We compare the
results to temperature and precipitation signals in PMIP3 models.