Hall, V.A. and Mauquoy, D. 2005. Tephra-dated climate- and human-impact studies during the last 1500 years from a raised bog in central Ireland. The Holocene 15: 1086-1093.
The authors conducted analyses on tephra, plant macrofossils and pollen from peat cored from Mongan Bog (53.33°N, 7.93°W), located on the east bank of the River Shannon in County Offaly in the Irish Midlands, to evaluate the effects of climatic and human impact in this region over the past 1500 years. They report that Zone C of their pollen diagram (~ AD 890-1270) "encompasses the time period during which the High Middle Ages occurred, therefore the reduction in local water-table depths may reflect warmer/drier conditions during this period of climatic amelioration."