The droughts that Europe has suffered over the past two decades, particularly since 2015, have been more severe than those in the past two millennia. This is what an international team of researchers assures this week that attributes the greater frequency of periods without rain to climate change caused by human action and warns of the effects on forests and crops.
Because, as the authors of this research published in the journal Nature Geoscience point out, prolonged droughts can have profound effects on both the environment and society. The latest examples have been the droughts of 2003, 2015, and 2018, the impact of which was felt on the health systems of the most affected countries and food production in Europe.
Our results show that what we have experienced over the last five summers is extraordinary for central Europe says Ulf Büntgen, professor at the University of Cambridge and leader of this research involving scientists from the Czech Republic, Germany, and Switzerland.
The researchers wondered whether central Europe had always suffered from such droughts in the past, but the lack of reliable meteorological records made it impossible to compare the current trend, perfectly monitored thanks to current technology, with what happened centuries and even millennia ago.
THE NATURE ARCHIVE
So they turned to nature’s archive: tree trunks. Buntgen and his colleagues reconstructed the chronology and severity of the droughts that have plagued central Europe in the last two millennia by analyzing a total of 27,089 rings of 147 oak trunks (living and dead) that have grown in the last 2,110 years.
They measured its composition, to independently quantify the oxygen and carbon isotopes of its rings since these vary depending on how the tree responds to heat stress and water. That is, its composition is different if the tree is exposed to high temperatures or if it receives rain.
By combining the data they read on living trees with those obtained from logs extracted from ancient buildings and archaeological sites, they were able to determine in which years there were droughts since 75 BC and which periods were wettest.
Thus, his analysis of the isotopes revealed that in the years 200, 720, and 1100 there were very humid summers while those of the years 50, 590, 950, and 1510 were very hot. The samples from the 2015-2018 period revealed more intense periods of drought than in previous periods without rain.
He concluded that the high interannual frequency of European droughts in the last two decades is unprecedented, even compared to the pronounced historical droughts of the 6th and early 16th centuries, during the Renaissance. Scientists suggest that changes in atmospheric circulation patterns due to climate change are primarily responsible for the recent increase in hot and dry European summers. The unprecedented forest extinction in much of central Europe supports our results according to Mirek Trnka, co-author, and researcher at the CzechGlobe Center.
