Abstract
The major early 20^th^ century climatic fluctuation (βΌ1920β1940) has been the subject of scientific enquiry from the time it was detected in the 1920s. The papers of scientists who studied the event firstβhand have faded into obscurity but their insights are relevant today. We review this event through a rediscovery of early research and new assessments of the instrumental record. Much of the interβannual to decadal scale variability in surface air temperature (SAT) anomaly patterns and related ecosystem effects in the Arctic and elsewhere can be attributed to the superposition of leading modes of variability in the atmospheric circulation. Meridional circulation patterns were an important factor in the high latitudes of the North Atlantic during the early climatic fluctuation. Sea surface temperature (SST) anomalies that appeared during this period were congruent with lowβfrequency variability in the climate system but were themselves most likely the result of anomalous forcing by the atmosphere. The highβresolution data necessary to verify this hypothesis are lacking, but the consistency of multiple lines of evidence provides strong support. Our findings indicate that early climatic fluctuation is best interpreted as a large but random climate excursion imposed on top of the steadily rising global mean temperature associated with anthropogenic forcing. Copyright Β© 2009 Royal Meteorological Society