NGRIP late Weichselian glacial age Bölling-Alleröd-Younger dryas methane amount data. Methane data is from source " Methane (CH4) record from the North Greenland Ice Sheet Project (NGRIP) ice core, Greenland, covering 32-11KYrBP, 10-17-2012 Authors: M. Baumgartner, A. Schilt, O. Eicher, J. Schmitt, J. Schwander, R. Spahni, H. Fischer, and T. F. Stocker