Mongabay: The Arctic should be growing cooler, but a new sediment core taken from an Arctic lake reveals that the lake’s ecology and chemistry has been transformed by unnatural warming beginning in the 1950s. The sediment core proves that changes happening in the lake during the Twentieth Century are unprecedented over the past 200,000 years. Headed by University of Colorado scientist Yarrow Axelford, the study retrieved the sediment core from the bottom of a thirty foot deep lake on Baffin …