Sedimentary sequences from glacial lakes in southern Norway provide a new approach to the reconstruction of a relatively complete record of Holocene glacier and climatic variations. The data show that, following the "Climatic Optimum" of the early Holocene, neoglaciation was asynchronous; glaciers formed at different times at different sites, depending on critical altitudinal thresholds in relation to the scale of climatic variations. Neoglaciation began as early as ca. 6400 yr B.P. at Gjuvvatnet, ca. 3400 yr B.P. at Midtivatnet, and later than ca. 1000 yr B.P. at Storevatnet. These differences in glacierization provide a key to reconstructing the fluctuating decline in mean summer temperature (relative to the present) from at least +1 °C during the mid-Holocene to below -2 °C in the "Little Ice Age."