Plain Language Summary
Future changes in global-mean temperatures have substantial implications
for climate-related risks, and global-mean temperatures will continue to
increase in response to carbon emissions (a property known as climate
sensitivity). In addition to long-term, human-driven warming, the global
surface temperature also exhibits short-term swings due to natural
climate variability. Recently, climate model experiments have shown some
evidence of a linear relationship between climate sensitivity and
climate variability, with potential applications for climate model
development and future predictions. We show that this relationship holds
when applied to paleoclimate data from the Common Era (850-1999) and use
the reconstructed temperature record over this period to estimate
climate sensitivity. Our analysis considers a period
(~1000 years) that is much longer than what has been
used in prior studies (~100 years) and thus paints a
fuller picture of past temperature variability. We show that interannual
and decadal fluctuations in climate could offer a novel technique for
assessing the Earth’s sensitivity to external forcing. Our results are
consistent with other lines of evidence, increasing confidence in our
approach. We hope our findings add value to the existing collection of
climate sensitivity estimates and encourage future use of paleoclimate
data to verify proposed constraints on climate quantities.