... Gradual warming is observed through the 20^th century (after 1935 A.D.), strongly intensifying between 1980 and 2003, which is in agreement with meteorological data. Between 1450 (+57, -66)¹ and 1800 (+17, -20), isotope levels were generally below average. This time period is generally called the Little Ice Age, e.g. defined by Lamb (1969) to have occurred from 1450–1850 A.D. Around 1020 A.D., the highest δ¹⁸O values of this record (-7.6‰ & -7.7‰) were observed in two samples covering about a 5-year time period and surrounded by other unusually high values. An average δ¹⁸O was calculated over a 30-year period (1005–1034 A.D.) centered at this anomaly and yielded -11.7±2.3‰. A t-test was applied showing that this was significantly higher than the average for the recent 27-years (1976– 2003) period: -13.1±2.4‰. Very high values were also observed around 740 A.D. This suggests that the Medieval Warm Period might have been even warmer than the last two decades of the 20^th century... (Chapter 4.3.9)

δ¹⁸O record 550–2003 A.D. The thin line represents raw data with decreasing temporal resolution, the thick line represents a smoothed spline function. The straight line represents the mean of the interpolated data (-13.6 ). The section between 1800 and 1976 A.D. was sampled at coarse resolution.