Boulder -- A U.S. study of a 200,000-year-old sediment core from an arctic lake indicates ongoing biological and chemical changes are likely caused by human activities.
The University of Colorado-Boulder-led study shows that while environmental changes at the Baffin Island lake during the past millennia have been tightly linked with natural causes of climate change -- like periodic wobbles in the Earth's orbit -- changes seen in the sediment cores since about 1950 indicate expected climate cooling is being overridden by results of human activity, such as greenhouse gas emissions.
