Background
The authors state that anthropogenically-induced climate change is projected by climate models to increase the frequency, severity and probability of extreme meteorological phenomena; and many climate alarmists claim that we have been experiencing this effect of global warming for some time now. Buntgen et al., on the other hand, write that a palaeoclimatic perspective is "indispensable to place modern trends and events in a pre-industrial context (Battipaglia et al., 2010)" and "to disentangle effects of human greenhouse gas emission from natural forcing and internal oscillation (Hegerl et al., 2011)," stating that it "remains unclear if long-term changes in climatic mean stages, such as those associated with the Medieval Climate Anomaly (AD ~900-1300), the Little Ice Age (AD ~1300-1850), and the Recent Global Warming (AD ~1850-present), [have] affected the probability of extremes."

What was done
To help develop this essential palaeoclimatic perspective, the nine researchers analyzed 11,873 annually-resolved and absolutely-dated ring-width measurement series from living and historical fir (Abies alba Mill.) trees that had been sampled across France, Switzerland, Germany and the Czech Republic, and which continuously spanned the AD 962-2007 period, while demonstrating that ring-width extremes were triggered by anomalous variations in Central European April-June precipitation.

What was learned
Buntgen et al. discovered there was "a fairly uniform distribution of hydroclimatic extremes throughout the Medieval Climate Anomaly, Little Ice Age and Recent Global Warming," which result brings into question, in their opinion, "the common belief that frequency and severity of such events closely relates to climate mean states."

What it means
For the portion of Europe involved in the study of Buntgen et al., extreme hydroclimatic phenomena were found to not be amplified in either number or strength in response to global warming, which leads one to suspect that the same likely holds true for other portions of the planet, in contradiction of vociferous climate-alarmist claims to the contrary.

References
Battipaglia, G., Frank, D.C., Buntgen, U., Dobrovolny, P., Brazdil, R., Pfister, C. and Esper, J. 2010. Five centuries of Central European temperature extremes reconstructed from tree-ring density and documentary evidence. Global and Planetary Change 72: 182-191.

Hegerl, G., Luterbacher, J., Gonzalez-Rouco, F.J., Tett, S., Crowley, T. and Xoplaki, E. 2011. Influence of human and natural forcing on European seasonal temperatures. Nature Geosciences 4: 99-103.