[U-02] 地球規模環境変化の予測と検出

[U02-P04] The timing of unprecedented hydrological drought under climate change

*佐藤 雄亮^1,2、芳村 圭³、ポカレル ヤドゥ⁴、金 炯俊⁵、塩竈 秀夫¹、横畠 徳太¹、花崎 直太¹、和田 義英^2,6、ブレック ピーター²、バイヤーズ エドワード²、ミュラーシュミ―ド ハネス^7,8、ゲーテン ディーター^9,10、オストベルグ セバスチアン⁹、ゴスリング サイモン¹¹、ブーランジェ ジュリアン¹、沖 大幹³ (1.国立研究開発法人国立環境研究所、2.国際応用システム分析研究所、3.東京大学、4.ミシガン州立大学、5.韓国科学技術院、6.ユトレヒト大学、7.フランクフルト ゲーテ大学、8.センケンベルグライプニッツ生物多様性・気候研究センター、9.ポツダム気候研究所、10.フンボルト大学、11.ノッティンガム大学)

キーワード：干ばつ、温暖化

Droughts that exceed the magnitudes of historical variation ranges could occur increasingly frequently under future climate conditions. However, the time of the emergence of unprecedented drought conditions under climate change has rarely been examined. Here, using multimodel hydrological simulations, we investigate the changes in the frequency of hydrological drought (defined as abnormally low river discharge) under high and low greenhouse gas concentration scenarios and existing water resource management and estimate the time of the first emergence of unprecedented regional drought conditions centered on the low-flow season. The times are detected for several subcontinental-scale regions, and three regions, namely, Southwestern South America, Mediterranean Europe, and Northern Africa, exhibit particularly robust results under the high-emission scenario. These three regions are expected to confront unprecedented conditions within the next 30 years with a high likelihood regardless of the emission scenarios. Additionally, the results obtained herein demonstrate the benefits of the lower-emission pathway in reducing the likelihood of emergence. The Paris Agreement goals are shown to be effective in reducing the likelihood to the unlikely level in most regions. However, appropriate and prior adaptation measures are considered indispensable to when facing unprecedented drought conditions. The results of this study underscore the importance of improving drought preparedness within the considered time horizons.