Background
The authors correctly indicate that instrumental station measurements, which systematically cover only the last 100-150 years, "hinder any proper assessment of the statistical likelihood of return period, duration and magnitude of climatic extremes," stating that "a palaeoclimatic perspective is therefore indispensable to place modern trends and events in a pre-industrial context (Battipaglia et al., 2010), to disentangle effects of human greenhouse gas emission from natural forcing and internal oscillation (Hegerl et al., 2011), and to constrain climate model simulations and feedbacks of the global carbon cycle back in time (Frank et al., 2010)."

What was done
To satisfy these requirements and help facilitate the accomplishment of the associated goals, Buntgen et al., as they describe it, "introduce and analyze 11,873 annually resolved and absolutely dated ring width measurement series from living and historical fir (Abies alba Mill.) trees sampled across France, Switzerland, Germany and the Czech Republic, which continuously span the AD 962-2007 period," and which "allow Central European hydroclimatic springtime extremes of the industrial era to be placed against a 1000 year-long backdrop of natural variations."

What was learned
The nine researchers found, in their words, "a fairly uniform distribution of hydroclimatic extremes throughout the Medieval Climate Anomaly, Little Ice Age and Recent Global Warming."

What it means
This finding, as they astutely state, "may question the common belief that frequency and severity of such events closely relates to climate mean states," which conclusion essentially rebuffs the well-worn climate-alarmist claim that global warming will lead to more frequent and severe floods and droughts. The odds are that if global warming didn't do so over the past thousand or more years, it likely won't do so in the future.

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.

Frank, D.C., Esper, J., Raible, C.C., Buntgen, U., Trouet, V., Joos, F. and Stocker, B. 2010. Ensemble reconstruction constraints of the global carbon cycle sensitivity to climate. Nature 463: 527-530.

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.