What was done
The authors employed "a network of about 1000 samples of tree-ring series ... that cover a significant part of the territory" of Spain to reconstruct thousand-year chronologies of temperature and precipitation.  They then used this data base to detect the occurrence of anomalies in these two parameters that varied from the mean by more than four standard deviations.

What was learned
The greatest concentration of very extreme climatic excursions was located between AD 1400 and AD 1600, during a period when extreme low temperatures reached their maximum frequency about AD 1500.  The authors refer to these anomalies as "the outstanding oscillations of the Little Ice Age."  They also note the existence of a period of below-normal temperature values from approximately AD 1920 to AD 1960, which was followed by predominantly above-normal values, but with frequencies far below those characteristic of the Little Ice Age.

What it means
We hear much these days about the great extremes of climate and weather that are predicted to accompany global warming.  However, as this paper demonstrates, much greater extremes (both above and below "normal") typically occur during colder, as opposed to warmer, periods, which can also be verified by consulting various reports we have posted in our Subject Index under the general heading of Weather Extremes.  Hence, we once again have a situation where the scare-mongering of climate alarmists is at variance with the testimony of the real world.