lModel-based estimates of
natural internal variability are an integral component of D&A research
lWhy do we rely on models
for these estimates?
ÆThey can be used to
perform the control experiments that we canÕt conduct in the real world
lWhy is it difficult to
estimate natural internal variability from observations?
ÆWe want to estimate noise on multi-decadal to century
timescales
ÆMost observational records are too short for this
purpose
ÆSignal and noise are convolved – difficult to
achieve unambiguous partitioning