Research press release


Nature Climate Change

An extreme future for California



今回、Daniel Swainたちの研究グループは、カリフォルニア州内でのこうした年々の異常乾燥と異常湿潤の急激な切り替わり[「降雨むち打ち事象(precipitation whiplash events)」と命名された]の発生頻度が、今後、人為的温暖化によってどのように変化するのかをモデル化した。Swainたちは、降雨むち打ち事象の発生頻度が21世紀末までに北カリフォルニアで25%高くなり、南カリフォルニアで最大100%高くなると予測している。このような変化の主たる原因は異常湿潤の増加であり、これは、すでに大きな州内の降水量の変動をさらに増幅する。こうした水循環の活発化によって、干ばつ時の水不足の軽減と豪雨時の洪水の防止の両面で、カリフォルニア州のインフラが強いプレッシャーを受けるようになると考えられる。

California is projected to swing from drought to extreme rainfall and flooding more often in the future, reports a study published online this week in Nature Climate Change. These results highlight the continuing challenge faced by the water infrastructure in the most populated state in the United States.

California has recently undergone a rapid hydrological change and its worst drought in recorded history plagued the entire state from 2010-2016. In the winter of 2016-2017, however, California was inundated by heavy rainfall and flooding - culminating in the Oroville Dam disaster that forced 250,000 residents to evacuate.

Daniel Swain and colleagues model how the frequency of these rapid, year-to-year transitions from extreme dry to wet conditions - which they dub ‘precipitation whiplash events’ may change in California’s future as a consequence of man-made warming. The authors predict a 25% rise in the frequency of precipitation whiplash events by the end of the twenty-first century in northern California, increasing up to 100% in southern California. These changes occur primarily due to an increase in wet extremes, which amplify the already variable precipitation across the region. This intensification of the water cycle will increase the pressure on California’s infrastructure to both alleviate water shortages during droughts and prevent flooding during heavy rain.

doi: 10.1038/s41558-018-0140-y


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。