Research press release


Nature Geoscience

Climate change: Unprecedented European droughts in the past two decades

過去20年のヨーロッパの乾期は、人為起源の気候変動のために、過去2110年間の他の乾期よりも厳しいものであったこと報告する論文が、今週、Nature Geoscience に掲載される。


今回、Ulf Buentgenたちは、過去2110年にわたり成長してきた中央ヨーロッパの147本のオークの高木から得た2万7080の年輪を分析することで、過去2000年にわたるヨーロッパの干ばつの時期と厳しさを再現した。Buentgenたちは、年輪の酸素と炭素の同位体組成を測定した。これらは、高木が水や熱のストレスに応答すると系統的に変化する。その測定結果を、生きている高木や古い建物・遺跡から採取した丸太の記録と組み合わせた結果、紀元前75年以降の特定の年に干ばつが起きたかどうかを明らかにすることができた。Buentgenたちは、過去20年間のヨーロッパの干ばつの、対前年比の高い発生頻度は、古代末期小氷期(6世紀ごろ)やルネッサンス期(16世紀初頭)の顕著な歴史的干ばつと比較しても、前例のないものであることを示している。


European dry spells during the past two decades have been more severe than others in the past 2,110 years due to anthropogenic climate change, reports a study published online this week in Nature Geoscience.

Prolonged droughts can have profound environmental and social effects; the European heat waves in the summers of 2003, 2015 and 2018 put pressure on food and health systems across the continent. However, understanding the causes and frequency of these droughts and how they compare to droughts in the past is hampered by a lack of reliable drought records prior to the keeping of high-quality meteorological observations.

Ulf Buentgen and colleagues reconstruct the timing and severity of European droughts over the last two millennia by analysing 27,080 growth rings from 147 oak trees from central Europe that grew over the past 2,110 years. They measure the oxygen and carbon isotope composition of the growth rings, which systematically change as the trees respond to water and heat stress. By combining records from living trees and logs pulled from old buildings and archaeological sites, they were able to determine whether a drought occurred in any particular year starting from 75 bce. They show that the high year-on-year frequency of European droughts in the past two decades is unprecedented, even compared to pronounced historical droughts during the Late Antique Little Ice Age (around the sixth century of the Common Era) and Renaissance (early sixteenth century of the Common Era).

The authors suggest that atmospheric circulation over the continent and the position of the jet stream represent the dominant drivers of historical drought occurrence in the region. Ongoing changes in these circulation patterns due to climate change, while complex, are likely to be responsible for the recent increase in dry, hot European summers.

doi: 10.1038/s41561-021-00698-0


メールマガジンリストの「Nature 関連誌今週のハイライト」にチェックをいれていただきますと、毎週各ジャーナルからの最新の「注目のハイライト」をまとめて皆様にお届けいたします。