What was done
Since instrumental data relative to floods of the Vistula River in Poland are only available after about 1945, the authors make use of documentary sources of information (written documents and "flood boards") to develop a reconstruction of the river's winter flooding all the way back to AD 988.

What was learned
Cyberski et al. write that "a look at the history of floods places the recent events in a broader perspective covering a period of over a thousand years," and that look indicates, in their words, that winter floods "have exhibited a decreasing frequency of snowmelt and ice-jam floods in the warming climate over much of the Vistula basin."

What it means
Over the period of time, i.e., the 20th century, when climate alarmists claim the world experienced a warming that was unprecedented over the past one to two millennia -- which extreme degree of warming is contended by them to lead to a variety of hugely negative impacts, including increasing floods -- the five researchers determined that conditions in the Vistula River Basin became less flood-prone in winter. Interestingly, Pfister (2005) indicates that that most of Central Europe has also become less drought-prone in winter during the 20th century. Consequently, 20th-century global warming has been accompanied by reductions in both floods and droughts in much of Central Europe, which is just the opposite of what the world's climate alarmists say should be the case on both counts.

Reference
Pfister, C. 2005. Weeping in the snow. The second period of Little Ice Age-type impacts, 1570-1630. In: Behringer, W., Lehmann, H. and Pfister, C. (Eds.) Kulturelle Konsequenzen der "Kleinen Eiszeit," Vandenhoeck, Gottingen, Germany, pp. 31-86.