Wang, L., Rioual, P., Panizzo, V.N., Lu, H., Gu, Z., Chu, G., Yang, D., Han, J., Liu, J. and Mackay, A.W. 2012. A 1000-yr record of environmental change in NE China indicated by diatom assemblages from maar lake Erlongwan. Quaternary Research 78: 24-34.
Working with a sediment core extracted from the center of Lake Erlongwan in the Long Gang Volcanic Field of Jilin Province, NE China (42°18'N, 126°21'E), Wang et al. dated its many layers with the help of radiometric 210Pb, 137Cs and 14C analyses, and identified and quantified the various species of diatoms contained in it. This work revealed the existence of three major intervals within their 1000-year record that they associated with "the Medieval Warm Period [AD 1050-1400], the Little Ice Age [AD 1400-1800] and the 20th century warming trend [AD 1900-2000]." And of the MWP, they say, first of all, that "the duration of the summer was longer while the spring and autumn were shorter than the 20th century," after which they unequivocally declare that "the period between ca. AD 1150 and 1200 was the warmest interval of the past 1000 years."