Abstract (from the online documentation):
A compilation of paleoclimate records from lake sediments, trees, glaciers, and
marine sediments provides a view of circum-Arctic environmental variability
over the last 400 years. From 1840 to the mid-20th century, the Arctic warmed
to the highest levels in four centuries. This warming ended the Little Ice Age
in the Arctic and has caused dramatic ... retreats of glaciers, melting of
permafrost and sea-ice, and alteration of terrestrial and lake ecosystems.
Although significant warming, particularly after 1920, was likely due to
increases in atmospheric trace-gases, the initiation of the warming in the
mid-19th century suggests that increased solar irradiance, decreased volcanic
activity, and feedbacks internal to the climate system played roles.
For graphics and discussion of the data from this paper, see the web site