If you can't explain the 'pause', you can't explain the cause...
Saturday, April 7, 2012
Paper: Extreme weather was as common during Medieval Warming Period & Little Ice Age
A paper published in Quaternary Science Reviews finds that, contrary to AGW predictions, the frequency and severity of weather extremes was similar to the present during the Medieval Warming Period and Little Ice Age.
A predicted rise in anthropogenic greenhouse gas emissions and associated effects on the Earth’s climate system likely imply more frequent and severe weather extremes with alternations in hydroclimatic parameters expected to be most critical for ecosystem functioning, agricultural yield, and human health. Evaluating the return period and amplitude of modern climatic extremes in light of pre-industrial natural changes is, however, limited by generally too short instrumental meteorological observations. Here we 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. Even though a dominant climatic driver of European fir growth was not found, ring width extremes were evidently triggered by anomalous variations in Central European April–June precipitation. Wet conditions were associated with dynamic low-pressure cells, whereas continental-scale droughts coincided with persistent high-pressure between 35 and 55°N. Documentary evidence independently confirms many of the dendro signals over the past millennium, and further provides insight on causes and consequences of ambient weather conditions related to the reconstructed extremes. A fairly uniform distribution of hydroclimatic extremes throughout the Medieval Climate Anomaly, Little Ice Age and Recent Global Warming may question the common belief that frequency and severity of such events closely relates to climate mean stages. This joint dendro-documentary approach not only allows extreme climate conditions of the industrial era to be placed against the backdrop of natural variations, but also probably helps to constrain climate model simulations over exceptional long timescales.
► 11,873 living and historical fir ring width samples were compiled across Europe. ► The world’s largest tree-ring composite continuously spans the AD 962–2007 period. ► Tree-ring extremes were triggered by April–June precipitation anomalies. ► Documentary evidence independently confirms dendro signals over the past millennium. ► Reconstructed extremes may constrain climate model simulations over long timescales.