2023-08-23 カリフォルニア大学サンタバーバラ校(UCSB)
◆研究は過去800年間の気象データを用い、温室効果ガスの影響について調査しました。結果として、太平洋ウォーカー循環の強度には大きな変化はなかったが、その年々の振る舞いが異なることが判明しました。これが将来の気象条件やリスクに影響を与える可能性があるとされています。また、火山噴火が太平洋ウォーカー循環に一時的な影響を及ぼし、エルニーニョの発生を引き起こすことも明らかになりました。
◆この研究結果は、気候変動の影響を理解し、将来の気象予測を信頼性のあるものにするために重要です。
＜関連情報＞
- https://www.news.ucsb.edu/2023/021177/el-nino-and-la-nina-multi-year-events-could-become-more-common
- https://www.nature.com/articles/s41586-023-06447-0
過去1000年間の太平洋ウォーカー循環の強制的変化 Forced changes in the Pacific Walker circulation over the past millennium
Georgina Falster,Bronwen Konecky,Sloan Coats & Samantha Stevenson
Nature Published:23 August 2023
DOI:https://doi.org/10.1038/s41586-023-06447-0
Abstract
The Pacific Walker circulation (PWC) has an outsized influence on weather and climate worldwide. Yet the PWC response to external forcings is unclear1,2, with empirical data and model simulations often disagreeing on the magnitude and sign of these responses3. Most climate models predict that the PWC will ultimately weaken in response to global warming4. However, the PWC strengthened from 1992 to 2011, suggesting a significant role for anthropogenic and/or volcanic aerosol forcing5, or internal variability. Here we use a new annually resolved, multi-method, palaeoproxy-derived PWC reconstruction ensemble (1200–2000) to show that the 1992–2011 PWC strengthening is anomalous but not unprecedented in the context of the past 800 years. The 1992–2011 PWC strengthening was unlikely to have been a consequence of volcanic forcing and may therefore have resulted from anthropogenic aerosol forcing or natural variability. We find no significant industrial-era (1850–2000) PWC trend, contrasting the PWC weakening simulated by most climate models3. However, an industrial-era shift to lower-frequency variability suggests a subtle anthropogenic influence. The reconstruction also suggests that volcanic eruptions trigger El Niño-like PWC weakening, similar to the response simulated by climate models.
